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By Carl F. Lutz, Robert F. Mehl

A layer of brass was formed on 0 brass using a vapor-solid reaction technique. The variation in composition with distance within the phase layer and across the a -ß interface was determined by an electron probe. The diffusivities were calculated as a function of concentration; the diffusion coefficient in brass was found to change by a factor of twenty-five over a compositional range of 8 at. pct. An explanation is proposed to account for the large change in the diffusivity, based on possible stresses in the diffusion zone; it is suggested that the concentration dependence of the thermodynamic factor might decrease the activation energy with increasing zinc content. ALTHOUGH the body of data on diffusion coefficients (D- values) in terminal solid solutions and in isomorphous systems is quite large, there is but little quantitative information for intermediate alloy phases. This paper recounts measurements of D-values for the ? phase in the Cu-Zn system. The experimental method employed consists in the forming of alloy layers and determining and analyzing the concentration-distance (c-x) curve. The experimental method employed could have been applied to several systems; the Cu-Zn system was chosen because the D-values in the a and ß phases are well known, and can thus be used for purposes of comparison. The rates of growth, of intermediate alloy layers are known for a number of systems. In nearly all cases the thickness varies parabolically with time, as to be expected if the rate of growth is controlled by the D-values. In a few cases, nonparabolic behavior has been noted.1 Nonparabolic growth may be the result of a) a variation of the composition at the phase interface with time, b) interface-controlled kinetics, c) short diffusion times coupled with long vacancy lifetimes (in vacancy diffusion),2 and d) crystal reorientation during diffusion in anisotropic systems.3 In the Al-Ni system4 and in the Al-u5 system parabolic growth kinetics are slowly approached after an initial transient period. In general those phases stable at a given temperature in a system A-B appear as separate phase layers when A and B are put in contact and given a diffusion he at-treatment. In most cases the compositions at the interface of adjacent phase layers are those read from the phase diagrams for the termini of the respective phases. This discontinuity in concentration is taken as independent of time, and the growth of one phase at the expense of another is assumed to be independent of interface kinetics, i.e., the rate of interface movement is controlled by volume diffusion in the phases concerned. wagner6 has given many solutions for multi-phase diffusion processes, assuming that the chemical diffusion coefficient, D, is independent of concentration, as have others. Jost7 has pointed out that the familiar Boltzmann-Matano solution is as valid for a (c-x) curve exhibiting concentration discontinuities at phase boundaries as for the usual single-phase case. Heumann and associates8,9 have applied this solution to the multi-phase case, but lacking concentration data within the several layers were forced to assume linear concentration gradients, thus calculating only average D-values. The purposes of the present study were: 1) to determine the dependence of D on concentration, 2) to calculate the intrinsic diffusion coefficients D?Cu and D?Zn, 3) to establish the time-law for the movement of the interface, 4) to determine the concentration limits at the ß-? interface, and, 5) to attempt to clarify the mechanism of diffusion. EXPERIMENTAL PROCEDURE The ? phase is exceedingly brittle; conventional solid couples and conventional sectioning methods were thus inapplicable. Vapor-solid couples were accordingly employed. Unfortunately the equilibrium vapor pressures of Zn for the ? phase are unknown; to escape this awkwardness, samples were enclosed in a capsule containing powder of an alloy of known composition, sufficiently large in quantity as to be effectively an infinite source, maintaining the concentration of Zn at the sample surface constant with time. The sources of Zn-vapor which can be employed in reaction with Cu, or a brass, or ß brass, to form a layer of ? brass satisfactorily wide in concentration range, are alloys of the phases ?, or ? + E or ? + d (depending on the temperature).

Jan 1, 1962

By Oliver Smalley

EXCEPT for the work of Guillet, who conducted a systematic investigation on the zinc-replacing value of nickel in brass, and extended his investigation with a view to developing commercial high zinc content nickel brasses, the author does not know of any systematic research on the subject. The most promising commercial alloys and their physical properties obtained by Guillet are given below: Maximum Elonga- Reduction Copper Zinc Nickel Stress, tion, of Area, Brinell Tons Per Per Cent. Per Cent. Sq. In. 55.0 41.0 5.0 24.4 46.5 94 Sand cast. 22.6 27.0 90 Chill cast. 56.7 39.74 3.35 30.0 43.0 51.7 97 Casting annealed 2 hr. at 750° C. 33.9 33.0 50.7 144 Cold-drawn bar. 55.15 42.3 2.24 29.8 33.0 116 Casting annealed 2 hr. at 750° C. 32.3 29.0 151 Cold-drawn bar. These test results scarcely justify the use of such quantities of so expensive a metal, and could have been obtained from ordinary commercial brass. For purposes of comparison, the physical properties of ordinary brasses, ranging from 70 per cent. to 50.1 per cent. Cu in both the cast and normalized1 conditions are included in Table 1. These incidentally furnish a useful standard of the properties of castings and of rolled, extruded and forged brass when correctly annealed. A close study of some of the well-known special brasses containing nickel reveals a series of alloys which bewilder by their complexity, and one can only hazard a guess at the function and commercial value of each of the many elements used.

Jan 10, 1925

Jan 1, 1935

By J. G. Eenink, R. A. Cunningham

One phase has been completed of a laboratory invesrigation of formations with relatively high permeability under conditions of overburden, formation and mud coltrmn pressures. The following statements are based on these tests within the limitations described. Drilling rate decreased when mud column pressure was greater than formation pressure. The decrease was primarily due to a layer of cuttings and mud particles held to the hole bottom by the difference in pressure. Much of the force of the bit was wasted in this layer and was unavailable for penetrating virgin formation. Adequate jet velocities helped clean the filter cake and chips away and resulted in increased drilling rate — the higher the jet velocity the faster the drilling rate. Drilling rate increased slightly when formation pres sure was greater than mud column pressure. The i11(reuse resulted from cleaning the hole bottom as formarion fluid flowed into the borehole. Overburden pressure had practically no effect on drilling rate. INTRODUCTION Some formations are difficult to drill in a wellbore hole but are easily drilled under atmospheric conditions in the laboratory. The reasons for this apparent difference in drillability are not fully understood. An increase in formation compressive strength causes a reduction in drilling rate. It has been shown by Griggs1, Handin2 and others3-1 that formation strength increases under conditions of high hydrostatic stress. Based on these results, a decrease in drilling rate would be expected with increased drilling fluid pressure in formations of low permeability having low formation fluid pressure. Such a decrease has been shown by Murray. et a1 and Eckel" This effect holds even when using nitrogcn under high pressure as the drilling fluid (unrc-ported tests from the Hughes laboratory). Poor bottom-hole cleaning may account for decreased drilling rates. Even though it may not be easily explained, evidence of poor cleaning can easily bc seen. One evidence is the increased drilling rate that accompanies decreased balling obtained with addition of oil in some muds used to drill shales.4,7,3 Many variables can affect drilling rates. These may include mud composition and properties, formation properties, bit types and operating conditions, formation fluid, mud column and overburden pressures. These must be studied a few at a time under carefully controlled conditions which simulate actual conditions as closely as possible. The purpose of this work was to investigate effect of overburden, formation and mud column pressures on drilling rates in permeable formations. These tests were suggested by conditions shown in Fig. I. Represented is a borehole drilled into a formation with relatively high permeability. In the vicinity of the hole bottom there exists a mud column pressure, P a formation fluid pressure, P and an overburden pressure, The mud has low water-loss properties and sufficient weight to more than overbalance the formation pressure. Laboratory investigation included a range with formation pressure greater than mud column pressure. NOMENCLATURE Pm mud column pressure = pressure of drilling fluid or mud at hole bottom Pf, formation pressure = pressure of fluid in intersticies of formation

By W. Weissberger, Frankiewicz, L. Pommier

Introduction In the U.S., about one-quarter of the fuel oil and natural gas consumption is associated with power production in utility and industrial boilers and process heat needs in industrial furnaces. Coal has been an attractive candidate for replacing these premium fuels because of its low cost, but there are penalties associated with the solid fuel form. In many cases pulverized coal in unacceptable as a premium fuel replacement because of the extensive cost of retrofitting an existing boiler designed to burn oil or gas. In the cases of synthetic fuels from coal, research and development still have a long way to go and costs are very high. Another option, which appears very attractive, is the use of solid coal in a liquid fuel form - coal slurry fuels. Occidental Research Corp. has been developing coal slurry fuels in conjunction with Island Creek Coal (ICC), a wholly-owned subsidiary. Both coal-oil mixtures and coalwater mixtures are under development. ICC is a large eastern coal producer, engaged in the production and marketing of bituminous coal, both utility steam and high quality metallurgical coals. There are a number of incentives for potential users of coal slurry fuels and in particular for coal-water mixtures (CWMs). First, CWM represents an assured supply of fuel at a price predictable into future years. Second, CWM is available in the near term; there are no substantial advances in technology needed to provide coal slurry fuels commercially. Third, there is minimal new equipment required to accommodate CWM in the end-user's facility. Fourth, CWM is nearly as convenient to handle, store, and combust as is fuel oil. Several variants of CWM technology could be developed for different end-users in the future. One concept is to formulate slurry at the mine mouth in association with an integrated beneficiation process. This slurry fuel may be delivered to the end-user by any number of known conveyances such as barge, tank truck, and rail. Slurry fuel would then be stored on-site and used on demand in utility boilers, industrial boilers, and potentially for process heat needs or residential and commercial heating. An alternative approach is to formulate a low viscosity pre-slurry at the mine mouth and to pipeline it for a considerable distance, finishing up slurry formulation near the end-user's plant. Finally, at the other extreme of manufacturing alternatives, washed coal would be shipped to a CWM manufacturing plant just outside the end-user's gate. Depending on fuel specifications and locations of the mine and end-user facility, any of these alternatives may make economic sense. They are all achievable in the near term using existing technology or variants thereof. The Coal-Water Mixture CWMs contain a nominal 70 wt. % coal ground somewhat finer than the standard pulverized ("utility grind") coal grind suspended in water; a complex chemical additive system gives the desired CWM properties, making the suspension pumpable and preventing sedimentation and hardening over time. Figure 1 shows the difference between a sample of pulverized coal containing 30 wt. % moisture and a CWM of identical coal/water ratio. The coal sample behaves like sticky coal, while the CWM flows readily. The combustion energy of a CWM is 96-97% of that associated with the coal present, due to the penalty for vaporizing water in the CWM. Potentially any coal can be incorporated in the CWM, depending on the combustion performance required and the allowable cost. CWMs are usually formulated using high quality steam coals containing around 6% ash, 34% volatile matter, 0.8% sulfur, 1500°C (2730°F) initial deformation temperatures, and energy content of 25 GJ/t (21.5 million Btu per st). Additional beneficiation to the 3% ash level can be accomplished in an integrated process. There are a number of minimum requirements which a satisfactory CWM must meet: pumpability, stability, combustibility, and affordability. In addition, a CWM should be: resistant to extended shear, generally applicable to a wide variety of coals, forgiving/flexible, and compatible with the least expensive processing. It was found that a complex chemical additive package and control of particle size distribution are necessary to achieve these attributes simultaneously, while maximizing coal content in the slurry fuel. Formulation of Coal-Water Mixtures A major consideration in the manufacture, transportation, and utilization of a slurry fuel is its pumpability, or effective viscosity. Most CWM formulations are nonNewtonian, i.e., viscosity depends on the rate and/or duration of shear applied. Viscosities reported in this paper were obtained using a Brookfield viscometer fitted with a T-spindel and rotated at 30 rev/min, thus they are apparent viscosities measured at a shear rate of approximately 10 sec-1. The instrument does reproducibly generate a shear field if spindle size and rotation rate are held fixed. By observing the apparent viscosities of several slurries at fixed conditions it is possible to obtain a relative measure of their viscosities for comparison purposes. A true shear stress-shear rate relationship at the shear rates at which the CWM will be subjected in industry may be obtained using the Haake type and a capillary viscometer. These viscometers are used for specific applications. However, for comparison purposes, apparent viscosities are reported.

Jan 1, 1985

By T. Toda, R. Maddin

A study has been made of the microstructure and mechanical properties of splat-cooled aluminum-base gold alloys with gold concentration from 0.25 to 5.0 wt pct. These alloys have been quenched from the liquid state by a torsion-catapult technique, which has made it possible to pepare specimens suitable for mechanical property measwements. From the electron micrographs it has been shown that the solid solubility of gold in aluminum can be extended to 2.5 wt pct (0.35 at. pct) by splat-cooling, while the maximum equilibrium solubility is known to be less than 0.3 wt pct (0.04 at. pct). The very fine grain size (several tenths of a micron), the extended solid solubility, and the fine dispersion of a second phase (AuAl2) contribute concurrently to a substantial strengthening effect. In Al-5 wt pct Au splat-cooled specimens of less than 50 thickness, the yield strength is 17 kg per sq mm or 6 times as large as the strength of bulk specimens. For the Al-1.0 to 2.5 wt pct Au solid solution obtained by splat-cooling, the yield strength reaches 7.5 kg per sq mm after an aging treatment (for 10 hr at 200°C), while it is 3.7 kg per sq mm for the corresponding bulk specimens. A great deal of research has been done in recent years on the structure and the properties of metals and alloys rapidly quenched from the liquid state.' The term "splat-cool" has been used with the meaning of a rapid quenching from the liquid state., The splat-cooling techniques have produced large numbers of new structures, which are expressed in terms of metastable phases,3 concentrated solid solutions,4 amorphous phases,5'6 new phases,7 and so forth. Nearly all previous studies have concentrated on the physical properties; i.e., crystallography, structure, electrical resistivity, magnetism, and so forth, of the splat-cooled metals and alloys. The mechanical strength of splat-cooled metals and alloys has hardly been investigated except for some recent work by MOSS' on A1-V alloys. The principle common to all experimental techniques developed to obtain very rapid quenching rates is based on the heat transfer by conduction. Liquid must be in good thermal contact with a substrate of high heat conductivity. Both of the published devices known as the "gun" and the "piston and anvil" techniques suffer from certain shortcomings. For example, the specimen obtained by the gun technique is very small and flaky, and hence inadequate for mechanical properties measurements. On the other hand if the material is forced to yield a continuous speci- men by the piston and anvil technique, it is probable that some plastic deformation occurs during the quench. A novel method for rapid quenching of a liquid metal or alloy, the "torsion-catapult", has been devised by Roberge and Herman9 at the University of Pennsylvania. In the apparatus the melt is thrown out of a curved furnace by a catapult and impinges on a copper substrate. The apparatus has the advantage of producing a continuous foil which is relatively large in size and of a quality suitable for the measurements of mechanical properties. The quenching rate is estimated to be of the order of l05 to l06 ºC per sec, (comparable to rates achieved by the piston and anvil technique). In selecting an alloy to be studied we were made aware of the fact that gold was believed to be "insoluble" in in and consequently age hardening in the A1-Au system appeared to be interesting. Quite recently Heirnendahl13-15 revealed that the solid solubility, as determined by transmission electron microscopy, was 0.3 wt pct Au at 640°C and 0.25 wt pct Au at 600°C, decreasing with decreasing temperature. In an A1-0.2 pct Au alloy after quenching from a solution treating temperature of 600°C the yield stress was 2 kg per sq mm, and it increased up to 6 kg per sq mm after aging for 1 to 10 hr at 200°C. The precipitation occurred in the form of platelike particles mainly on (100) matrix planes. The intermediate phase n', the equilibrium phase n (AuAl2), and lattice relationships between both precipitates and the matrix were also investigated by electron microscopy. One of the purposes of the present research is to determine whether or not the solid solubility in this system, in which gold has a very small solubility in

Jan 1, 1970

By W. S. Hyler, L. W. Berger, R. I. Jaffee

Hydrogen additions of 390 ppm to A-55 titanium and 368 ppm to Ti-8 pet Mn have no deleterious Hydrogenadditionseffect on the unnotched and notched rotating-beam fatigue properties of these materials. 'These amounts of hydrogen, however, are sufficient to cause severe notch-impact thesematerials.embrittlement in A-55 titanium and pronounced loss of tensile ductility in Ti-8 pet Mn. The lack of embrittling effect in fatigue in the latter alloy is consistent with the postulated strain-aging mechanism of hydrogen embrittlement in a-ß alloys. There is a significant strain-agingincrease in the unnotched endurance limit of A-55 titanium with the addition of hydrogen. This increase may be explained as the result of internal heating effects which would dissolve the hydride and cause solid-solution strengthening. TITANIUM and its alloys may be seriously embrittled by relatively small amounts of hydrogen. The form which this embrittlement takes has been shown to vary with alloy type. The a alloys, for example, suffer most strongly from loss of notch-bend impact toughness' when sufficient hydrogen is added, and this effect has generally been associated with the presence of hydride phase in the micro-structure. In a-ß alloys, on the other hand, hydrogen is most detrimental to tensile ductility in slow-speed tests,2-1 and the embrittlement may be detected in a most convincing manner by means of rupture tests at room temperature. This particular kind of embrittlement has not been associated with a change in microstructure, but has been classified rather generally as associated with a strain-aging type of mechanism.' In the present paper, the effect of an embrittling amount of hydrogen on the rotating-beam fatigue properties of both an a and an a-ß titanium alloy is covered. For this study, annealed commercially pure (A-55) titanium was chosen as an a alloy, and equilibrated and stabilized Ti-8 pet Mn as representative of a typical a-ß alloy. Nominal hydrogen levels of 20 and 400 ppm were evaluated, the latter amount having been shown previously to be severely detrimental to the impact toughness of commercially pure titanium and to cause pronounced strain-aging embrittlement in the Ti-8 pet Mn alloy. The only report of the effect of hydrogen on the fatigue properties of titanium is given by Anderson et al.,° in which a push-pull type of fatigue test was conducted on as-received commercial-purity titanium sheet. Much scatter was found in the results, but generally the presence of hydrides slightly decreased the fatigue strength of unnotched specimens in the longitudinal direction. The results of notched tests were masked too greatly by scatter to be significant. Experimental Procedure Preparation of Materials—Analyses of the A-55 titanium and the Ti-8 pet Mn alloy used in this investigation are given in Table I, which indicates the 8 pet Mn alloy to be more nearly a 6 pet Mn alloy. This alloy will be referred to as Ti-8 pet Mn, however, since this is the commercially designated composition. Both alloys were received in the form of5/8-in. diam rod and, after suitable surface preparation, 5-in. lengths were vacuum annealed at 820°C. Half of the rods for each material were then hydrogenated at 820°C to a nominal hydrogen content of 400 ppm. The hydrogenated and vacuum-annealed A-55 rods were hot swaged at 700°C from 5/8-in. diam to 1/4-in. diam, and then annealed 1 hr at 800°C and air cooled prior to preparation into test specimens. Fabrication of the Ti-8 pet Mn alloy was by hot swaging to 3/8-in. diam at 760" and then 1/4-in. diam at 704°C. This material was then annealed 1 hr at 704", followed by furnace cooling to 593"C, and finally air cooling to room temperature. Evaluation—In order to examine more completely the effects of hydrogen on the particular materials studied, slow-speed tensile and notch-bend impact properties were determined in addition to fatigue data. Tensile specimens were of the standard ASTM type with a reduced section of 1/8-in. diam and a gage length of 1/2 in. A subsize cylindrical Izod specimen was used for impact tests. These specimens had a 45" notch with a 0.005-in. radius and a 0.150-in. root diam, and the stress concentration factor of this notch in bending was Kr = 3. Both the ten-

Jan 1, 1959

By H. Conrad, V. V. Damiano, G. J. London

The slip mode activated during the c axis compression of single crystals of commercial-purity ingot SR beryllium, high-purity (twelve-zone-pass) beryllium, and Be-4.4 wt pct Cu and Be-5.2 wt pct Ni alloys in the temperature range of 25° to 364°C was determined using two-surface slip trace analysis, slip-step height analysis, and electron transmission microscopy. All three techniques indicated the occurrence of copious pyramidal {1 122) (1123) slip in the alloys over the entire temperature range, the amount increasing with temperature. Pyramidal slip was also indicated in the high-purity beryllium by slip trace analysis and electron transmission microscopy, but the amount was somewhat less than in the alloys. For the commercial-purity ingot crystals, only a very small number of pyramidal slip lines were observed, and these were in the immediate vicinity of the fracture surface. No pyramidal dislocations could be detected by electron transmission microscopy in this material. Dislocatransmissiontions with Burgers vectors [0001] and +(ll20) were identified by electron transmission microscopy inthe (1122) slip bands, as well as those with the j (1123) vector. This was interpreted to indicate that the edge components of the 3(1123) vector dislocations activated during c axis compression dissociate upon unloading according to the reaction i (1123) — [0001] + 3(1120) THE microstrain c axis compression of single crystals of commercial-purity ingot SR beryllium (99.6 pct), high-purity twelve-zone-pass beryllium (99.98 pct), Be-5.24 pct Ni and Be-4.37 pct Cu alloys was described in a previous paper.1 This paper covers in detail the analysis of slip traces observed on two mutually perpendicular lateral surfaces of these specimens, and a detailed description of transmission electron microscopy studies performed on foils cut from the bulk crystals after they had been deformed to fracture in the c axis compression. Observation of slip traces on single surfaces of deformed single crystals are generally insufficient to positively identify slip or twinning modes. The use of two carefully cut and oriented perpendicular surfaces can greatly aid in the positive identification and index- ing of slip traces, although even this technique may be quite inadequate if more than one type of slip system operates and if an insufficient number of traces are observed on the surfaces. The problem is greatly simplified for symmetric cases like that for c axis compression of an hep crystal such as beryllium, in which the operating slip systems are all equally inclined to the direction of the applied stress, and each slip system of a given slip mode has an equal chance of operating. For such cases, the traces of any given slip mode observed on the surfaces cut parallel to the c axis are symmetrically tilted about the c axis. It is therefore possible to quickly determine whether one or more slip modes are operating. Confirmatory evidence in support of the observations made on the external surfaces can be obtained from foils cut from the deformed crystals and examined by transmission electron microscopy. This latter technique serves to identify not only the operating slip plane but also the Burgers vector of the dislocations which participate in the slip. For this purpose, a simplified technique based upon a double tetrahedron notation is used in the present paper. The planes and directions in the hep lattice are all designated by letters rather than indices and extinction conditions are easily determined if the Burgers vector lies in the plane contributing to the diffraction. RESULTS 1) Slip Trace Analysis. The standard (0001) stereo-graphic projection of beryllium is shown in Fig. 1. The two mutually perpendicular, lateral surfaces of the compression specimen are represented by the diametrical planes AA' and BB', also referred to as surface A and surface B. For the specific case represented (a Be-5.24 pct Ni specimen deformed by c axis compression at room temperature), the A surface is tilted 5 deg to the (10i0') plane and the B surface is tilted 5 deg to the (1120) plane. Two surface trace analyses may be facilitated by examining in turn the intersection of various great circle traces of specific pyramidal planes with two surfaces and comparing the angles made with the (0001) plane with those actually observed on the two surfaces. One then identifies the slip traces by trial and error on a best-fit basis. The (1122) type planes (it was found that slip occurred on these planes) are shown plotted on the stereographic projection in Fig. 1. One obtains directly the angles between the (0001) plane and the {1122) traces by measuring the angle from the periphery to the point of intersection along the lines

Jan 1, 1969

By Lawrence H. Van Vlack, Otta K. Riegger

Periclase-type oxides were examined microscopically after being exposed to siliceous liquids. The rate of grain growth was found to be inversely proportional to the grain diameter. Grain growth proceeds more rapidly at higher temperatures, but is retarded by increasing liquid contents. aMag-nesiowiistites with higher MgO contents grow less rapidly than those with higher FeO contents. The growth rate is reduced by the presence of a second solid phase. The silica-containing liquid penetrates as a film between the individual magnesiowus tite grains. This is independent of time, temperature, amount of liquid, or the MgO/ Fe0 ratio. When present, olivine and spinel-type phases can provide a solid-to-solid &apos;&apos;bridge" between magnesioustite grains. THIS paper presents the results of a study of the microstructures of periclase type oxides in the presence of a silicate liquid. The purpose was to learn more about the effect of service factors such as 1) time, 2) temperature, and 3) liquid content upon A) grain growth, and B) liquid location among the solid grains. This study was prompted by the fact that periclase refractories are known to have very little solid-to-solid contact when the phases which are present are limited to periclase and liquid. Such a micro-structure gains industrial significance because it permits fracture during service when stresses are applied at high temperatures. The details of ceramic microstructures have not received extensive attention. This is in contrast to the extensive attention given to a) the phase relationships pertaining to refractory compositions, and b) the details of the microstructures of comparable metallic materials. A brief review will be made of the pertinent phase relationships and microstructural considerations in general, as well as of refractory compositions. a) Phase Relationships. This investigation was limited to those compositions in which (Mg, Fe)O was the solid phase. MgO and FeO form a complete series of solid solutions. Pure MgO has the name of periclase. The related FeO structure is called wustite. Both have the NaC1-type structure: however, wustite possesses a cation deficiency so that the true composition is Fe<10 even in the presence of metallic iron. The phase relationships involving solid (Mg, Fe)O and a silicate liquid are shown in Fig. 1. In this case. the liquid is saturated with (Mg, Fe)o. There-fore its SiOz content is below that encountered in orthosilicate liquids. As a consequence the liquid phase specie:; are primarily the following ions: and 0-&apos; plus occasional Fe+ ions. Two features are of importance: a) the liquid contains relatively small species and b) the liquid contains large quantities of the same species as the solid. viz., Fig. 2 shows the system, FeO-SiOz, which will be used in some of the discussions that follow. This diagram is the right side, vertical section of Fig. 1. Here, as pre\iously, the composition at the FeO end of the diagram is nonstoichiometric, varying from Feo.950 when the liquid oxide is in contact with the solid iron, to about Fe 0, when the solid oxide is in equilibrium with an atmosphere of equal proportions of CO and C02 at the solidus temperature. The Fe/O ratio will be maintained in wustite in the presence of SiO,. However, the FeM/Fe++ ratio in the liquid will be lower because of the effect OIF the SiO, on the activity of the FeO. With the addition of MgO to wustite, the over-all composition (IvZg, Fe)@, has a value of x lying between 0.9 and 1.0 when the COz/CO ratio is 1.0&apos;. b) Microstructures. In general, published attention to refractory microstructures has been directed toward the phase analyses that accompany compositional variations. This is illustrated by Harvey6 in his work on silica brick and by wells7 in his work on periclase brick. In each case, a series of altered zones is encountered which provides a sequence of phase associations. If due consideration is given to reaction kinetics, such an examination reveals phases that are compatible with equilibrium studies. Admittedly, however, it is often necessary to determine more complicated polycomponent systems to account for all the phases present.8 Relatively little attention has been given to microstructural geometry in ceramic materials. Certainly less attention has been given to this aspect of ceramic microstructures than to the size, shape, and distribution of the constituent phases in metals. Burke has pointed out that the grain size of oxides follows the same growth rules as for metals, viz.,

Jan 1, 1962

By J. J. Gilvarry, B. H. Bergstorm

The first part of this paper describes a new approach to the problem of energy relationships in fracture and comminution. The basic theoretical method used (as contrasted to previous empirical or semi-empirical approaches) is an attempt to verify or disprove the hypothesis of von Rittinger, In the second part of the paper, theoretical conclusions for the three headings of single fracture, plural fracture, and comminution are tested. Agreement between theory and experimental results is demonstrated. The classical hypotheses on the energy relationship in brittle fracture are those of von Rittinger-that the energy required is proportional to the new surface formed— and the alternative one of Kick.&apos; Over the years, repeated attempts have been made to discriminate experimentally between the two assumptions, or to replace both of them, as has been done by Bond? However, no semblance of agreement seems to exist among different investigators. This paper is the first in a series essaying a new approach to the entire problem of energy relationships in fracture and comminution. The purpose of this program of research is to verify (or disprove) the hypothesis of von Rittinger. In contrast to previous empirical or semi-empirical approaches to the problem, the basic method adopted is theoretical. The prime aim is to determine the distribution function for fragment size theoretically and to verify the predicted distribution experimentally. This approach should make possible determination of the total surface of the particles by integration over the corresponding distribution function; one may hope that this direct procedure will yield more definitive results than use of gas adsorption or other methods. The surface area so obtained can then be compared with experimental energies, as obtained by Bergstrom, Sollenberger, and Mitchell,4 for example. It is convenient to distinguish between single fratture, plural fracture, and comminution. Single fracture of a brittle solid is defined as fracture by an external stress system which is removed instantly and permanently when fracture is initiated. Plural fracture consists of single fracture of the original specimen, followed by a sequence of only a few secondary fractures; comminution differs in that the sequence of secondary fractures consists of a large number of repetitive steps. For single fracture, Gilvarrys has given a rigorous derivation of the proper distribution function for fragment size, based on a closely defined physical model and deduced strictly by the laws of probability. Gilvarry and Bergstrome have compared the predictions of the theory with experiment, and have found excellent agreement. The prior work of Gilvarry and of Gilvarry and Bergstrom considers only single and plural fracture. The purpose of the present paper is to extend the discussion to the case of comminution. For prefatory purposes, the theory of Gilvarry for single fracture will be outlined. The considerations will then be applied to the cases of plural fracture and comminution. SINGLE FRACTURE The derivation is based on the Poisson law.7 For Points distributed with mean density y over a domain, this law states that the probability p(t)dt of one point lying in the range t to t + dt with none in the interval 0 to Ms p(t)dt = ye-yt dt. For this distribution to be valid, it is necessary and sufficient that the points be distributed at random, individually and collectively in the sense of ~~~.7 The former qualification requires that the position of One Point be independent of another, and the latter implies that the probability of a region containing a

Jan 1, 1961

By Roland de Wit

Conclusions reached in a paper by weertmanl are amplified in a mathematical and graphical way. It is shown that in a stressed crystal a straight dis-location may be in a position of unstable equilibrium with respect to helix development, and how a small perturbation may start the dislocation off on its helical path. Helix development occurs by diffision; bulk diffusion is necessary for development from a screw, but core diffision is sufficient for development from an edge dislocation. For a mixed dislocation helix development can take place by core diffusion if the helix also climbs; a diffusion reversal takes place when the slope of the helix equals the slope of the Burgers vector. The work done on a crystal by the external forces is graphically shown to be consistent with the direction of motion of the dislocation in helix development. Finally a detailed mechanism for tangle formation from helices is presented. In the course of helix development a glide situation may be reached where a segment of each helix loop lies in a slip plane in which it can expand by glide. Thus is it visualized how a helix can deteriorate into a tangle. A paper by weertmanl proposes dislocation-tangle formation by a helical dislocation mechanism. The present paper amplifies Weertman&apos;s arguments in a mathematical and graphical way and presents some further ramifications of the proposed model. The importance of dislocation tangles is discussed in Weertman&apos;s paper and the references cited therein. The mechanism of their formation is not yet understood. Weertman proposes that in cold-worked crystals conditions exist suitable for the conversion of straight dislocations into helices and subsequently into tangles. Helix formation occurs by a diffusion process and Weertman proposes that at low temperatures only core diffusion is important. The present paper necessarily repeats some of Weertman&apos;s work. Since the mathematical development and notation used are slightly different from his, this was thought necessary for clarity. GEOMETRY OF THE HELIX weertman2 has shown that the equilibrium form of any dislocation line is a helix if it is assumed that the energy per unit length (line tension) of the dis- location is constant. For the special case that no external forces act on the dislocation, the helix reduces to a straight line. We shall assume in this paper that the dislocation has a helical form even when it is not in equilibrium. The parametric equation of a helix is, see Fig. l: where a is the radius of the cylinder tangent to the helix, and 270 the pitch of the helix. The pitch is related to v, the number of turns per unit length (along the axis) by the relation: When a = 0 Eq. [I] gives a straight line in the z direction. The growth of a straight dislocation into a helix is now described mathematically by letting a vary from zero to its final value. The tangent to the helix is given by where is the path length along the helix. This gives the direction of t and since its magnitude is unity we must have So that dcp/ds = (a2 +p2)-"&apos;. The curvature of the helix is given by where n = -(cos + sin) is a unit vector normal to the helix. Note that the vectors k and n always point toward the axis of the helix, Fig. 1. FORCE ON THE HELIX The external force which makes the straight dis-

Jan 1, 1963

By M. D. Cooper

UNDERGRADUATES in mining engineering may be prepared for work by giving them sound instruction in the courses generally considered essential to the profession. The industry is not deeply concerned about the details of those courses. The average man in the coal industry does not wish to insist upon a rigid program. Therefore, he differs little from those in the teaching profession who evidently are not unanimous in their opinions, or all college catalogs would be alike. For the good of the profession, it is just as well that there should be differences in regard to details. It appears that students graduating in mining engineering from the accredited institutions receive similar instruction. It is taken for granted that the graduate will have a good understanding of English, mathematics, mechanics, electricity, chemistry, physics, geology, and surveying, in addition to his major courses in mining. Somewhat belatedly, industry hopes he will have had at least an introduction to the subject of labor relations, the importance of which is only too clear at present. The coal industry expects, of course, that students in mining engineering will be taught the strictly mining subjects by men who have had practical experience in the mines and who keep themselves well informed in regard to current methods. While the undergraduate is subject to the control of members of the teaching profession, industry expects him to be trained in certain ways that are not a part of his textbooks, but can be made an inseparable part of his development by the skillful supervision of his teachers. Of the desired characteristics, dependability is of the utmost importance. Probably most employers would overlook certain short-comings if the young graduate demonstrated that he was thoroughly dependable. If he always appeared at the right place at the right time with the proper equipment, he would soon be well established as a welcome member of his organization. The graduate who gets a reputation for being undependable will have little opportunity for advancement. Closely allied to dependability is loyalty. Athletic teams and social groups in college tend to develop loyalty which may well be carried over into industry. This does not mean that the graduate has to be satisfied with customary practices. The average manager is glad to see the graduate make constructive criticism as long as he demonstrates his loyalty at the same time. It is important that his loyalty keeps him alert arid ready to take helpful action for the benefit of his organization, and especially to stand with it during times of stress. With or without an introduction to labor relations in college, the graduate is expected to develop ability in this most important field. Beginning with himself, he will find it essential to deal agreeably with his immediate associates. Getting along in friendly fashion with his own small group will be a great help as his responsibilities increase and he is required to deal with larger numbers of persons. On a higher scale, his interest in his community may grow at the same time by voluntary work in any one of a great number of useful activities. Industry expects the graduate engineer to be a mature man at the time he gets his first job. Supposing that he has better than average intelligence, industry expects him to continue to grow intellectually and to fit himself for responsible jobs when they are offered to him. For this reason, employers are apt to look over his college record to see what he did that would indicate his fitness for leadership. There is interest in knowing what he did beyond the requirements. As evidence of his mental growth, it is expected that the graduate will do independent thinking; that he will not take too much for granted. When he reads a report, he should develop the ability to see whether the subject is new or whether it is just a description of an old method that has been superseded by something better. For the same reason, the graduate should be able to accept conditions that have been arrived at by sound experience rather than cling to something else that seems better in theory. In this connection, it may be remarked that the ability to operate successfully a personal budget will be noteworthy, as it may be assumed that a man who knows how to conduct his own affairs will be prepared to assume the larger responsibilities of industry. Membership in AIME will indicate to the employer that the graduate is interested in the mining industry as a whole. Therefore, it is good evidence of something more than a local outlook. Quite apart from college training and mental ability, the newly employed graduate will be expected to be willing to do hard manual labor for a time. This will give him an understanding of the actual conditions of work done by those he supervises later. He will gain their confidence and be able to see that the work is carried on in a safe and efficient manner. Part of this experience may be acquired in his summer vacations during his undergraduate career. Such work would make a favorable impression on a prospective employer, especially if the graduate showed a willingness to continue it until he was prepared for something better. To summarize, the man in authority in the coal industry will not quarrel with the professor of mining engineering over details of curriculum. He will be pleased if the school sends him graduates who possess a good foundation in the courses studied, and who may be depended upon to do their work faithfully and intelligently. Such men will be ready when the time comes to assume their places as leaders of an essential industry.

Jan 1, 1951

By M. D. Cooper

UNDERGRADUATES in mining engineering may be prepared for work by giving them sound instruction in the courses generally considered essential to the profession. The industry is not deeply concerned about the details of those courses. The average man in the coal industry does not wish to insist upon a rigid program. Therefore, he differs little from those in the teaching profession who evidently are not unanimous in their opinions, or all college catalogs would be alike. For the good of the profession, it is just as well that there should be differences in regard to details. It appears that students graduating in mining engineering from the accredited institutions receive similar instruction. It is taken for granted that the graduate will have a good understanding of English, mathematics, mechanics, electricity, chemistry, physics, geology, and surveying, in addition to his major courses in mining. Somewhat belatedly, industry hopes he will have had at least an introduction to the subject of labor relations, the importance of which is only too clear at present. The coal industry expects, of course, that students in mining engineering will be taught the strictly mining subjects by men who have had practical experience in the mines and who keep themselves well informed in regard to current methods. While the undergraduate is subject to the control of members of the teaching profession, industry expects him to be trained in certain ways that are not a part of his textbooks, but can be made an inseparable part of his development by the skillful supervision of his teachers. Of the desired characteristics, dependability is of the utmost importance. Probably most employers would overlook certain short-comings if the young graduate demonstrated that he was thoroughly dependable. If he always appeared at the right place at the right time with the proper equipment, he would soon be well established as a welcome member of his organization. The graduate who gets a reputation for being undependable will have little opportunity for advancement. Closely allied to dependability is loyalty. Athletic teams and social groups in college tend to develop loyalty which may well be carried over into industry. This does not mean that the graduate has to be satisfied with customary practices. The average manager is glad to see the graduate make constructive criticism as long as he demonstrates his loyalty at the same time. It is important that his loyalty keeps him alert arid ready to take helpful action for the benefit of his organization, and especially to stand with it during times of stress. With or without an introduction to labor relations in college, the graduate is expected to develop ability in this most important field. Beginning with himself, he will find it essential to deal agreeably with his immediate associates. Getting along in friendly fashion with his own small group will be a great help as his responsibilities increase and he is required to deal with larger numbers of persons. On a higher scale, his interest in his community may grow at the same time by voluntary work in any one of a great number of useful activities. Industry expects the graduate engineer to be a mature man at the time he gets his first job. Supposing that he has better than average intelligence, industry expects him to continue to grow intellectually and to fit himself for responsible jobs when they are offered to him. For this reason, employers are apt to look over his college record to see what he did that would indicate his fitness for leadership. There is interest in knowing what he did beyond the requirements. As evidence of his mental growth, it is expected that the graduate will do independent thinking; that he will not take too much for granted. When he reads a report, he should develop the ability to see whether the subject is new or whether it is just a description of an old method that has been superseded by something better. For the same reason, the graduate should be able to accept conditions that have been arrived at by sound experience rather than cling to something else that seems better in theory. In this connection, it may be remarked that the ability to operate successfully a personal budget will be noteworthy, as it may be assumed that a man who knows how to conduct his own affairs will be prepared to assume the larger responsibilities of industry. Membership in AIME will indicate to the employer that the graduate is interested in the mining industry as a whole. Therefore, it is good evidence of something more than a local outlook. Quite apart from college training and mental ability, the newly employed graduate will be expected to be willing to do hard manual labor for a time. This will give him an understanding of the actual conditions of work done by those he supervises later. He will gain their confidence and be able to see that the work is carried on in a safe and efficient manner. Part of this experience may be acquired in his summer vacations during his undergraduate career. Such work would make a favorable impression on a prospective employer, especially if the graduate showed a willingness to continue it until he was prepared for something better. To summarize, the man in authority in the coal industry will not quarrel with the professor of mining engineering over details of curriculum. He will be pleased if the school sends him graduates who possess a good foundation in the courses studied, and who may be depended upon to do their work faithfully and intelligently. Such men will be ready when the time comes to assume their places as leaders of an essential industry.

Jan 1, 1951

SAFETY in open-pit mining receives a minimum of notoriety, but its significance in profitable and efficient operation is as great as in other methods of mining. Open-pit operators from Arizona, New Mexico, and Mexico, exchanging ideas on safety at a symposium during the recent annual meeting of the Arizona Section, AIME, discovered unanimity of opinion that the successful safety program depended on managerial and supervisory support with the vigorous cooperation of the employes. Safety Organization The operation of a safety program is dependent on the ability of management to project enthusiasm through the company organization. This requires a suitable method of communication to the supervisory and employee levels so as to approach them in a manner that will inspire cooperation. Safety committees comprised of various combinations of managerial, supervisory, and employe personnel are frequently used for this purpose. The open-cut mine of the Chino Division of the Kennecott Copper Corp., Santa Rita, N. Mex., operates its program through management, a full-time safety engineer, and two safety committees, the Departmental and Shops Safety Committee and the Central Safety Committee. The Departmental and Shops Committee consists of one employe from each department and shop and the safety engineer. The selected members serve for a period of one month. This committee meets once a month, the only representative of management being the safety engineer because it is believed that employes will speak more freely when their supervisors are not present. The duties of the committee are to report hazardous conditions and make recommendations, but the committee has no authority to approve or disapprove. The Central Safety Committee is comprised of supervisory personnel from all departments and shops, and one member of each of the five bargaining organizations. Members of this committee are permanent and hold meetings soon after the departmental group to take action on recommendations of the latter. The committee system insures participation of all levels of personnel in the accident-prevention program, thereby stimulating safety consciousness. The New Cornelia branch of the Phelps-Dodge Corp., uses three groups to conduct the safety program; the General Safety Committee, Division Safety Committee, and the operating-unit safety meetings. The unit safety meetings provide for active participation of employes in discussion of various phases of the program. Within these groups vigorous opinions regarding safety are often expressed and the workmen are critical if they recognize a digression from the adopted safe-practice procedures. These monthly discussions give the program vitality. The Division Safety Committee is composed of the division superintendent and the division department heads, and follows an established pattern in discussion of all phases of the safety program. The General Safety Committee, made up of the manager, division, and department heads, makes decisions on policies and procedures; it renders decisions on recommendations and suggestions. Management at the New Cornelia branch feels this system of safety committees and meetings has been active in advancing the program. Safety Codes In the open-pit mines of the Southwest, a safety code for operation or service of equipment, methods

Jan 1, 1952

By R. B. Campbell

One of the three power plants that will be in the Curecanti Unit of the Bureau of Reclamation&apos;s Colorado River Storage Project is the power plant at Morrow Point Dam. Presently under construction, the Morrow Point Power Plant is between Gunnison and Montrose on the Gunnison River in west-central Colorado. (Fig. 1). Morrow Point Dam will be a thin, double-curvature, concrete-arch dam, 465 ft high and will impound 120,000 acre-ft of water. Two 60,000-kw hydroelectric generators will be housed in an underground power plant in the left abutment just down- stream from the dam. The power-plant chamber will be an unlined opening 205.5 ft long, 57 ft wide and 65 to 134 ft high. The arch-type roof with a rise-to-span ratio of 1 to 4 will be supported with rock bolts and chain link fence. A description and discussion of the design considerations for the power-plant opening and rock bolt design are given by William H. Wolf, Gilbert L. Brown, and Ernest D. Morgan in "Morrow Point Under- ground Powerplant," ASCE Power Division Specialty Conference, Denver Colorado, August 18-20, 1965. The Morrow Point site is in a moderately active region of mild earth- quakes, as evidenced by recent earthquakes in 1960 and 1962. Therefore, the Bureau of Reclamation undertook an investigation of the effects on the underground power-plant chamber when subjected to an earthquake. The art of earthquake engineering has been directed primarily at developing methods of analyzing the nature of ground surface motions and designing surface structures to resist damage from vibrations impressed on the structure by the ground motions. The mechanism of straining an underground cavity by an earthquake

Jan 1, 1968

By W. W. Whitaker, C. W. Manry, R. H. McLean

In an eccentric annulus, cement may favor the widest side and bypass slower-moving mud in the narrowest side. Tendency of the cement to bypass mud is a function of the geometry of the annulus, the density and flow properties of the mud and cement and the rate of flow. Bypassing can be prevented if the pressure gradient protluced from circulation of the cement and buoyant forces exceeds the pressure gradient necessary to drive the mud through the narrowest side of the annulus at the same velocity as the cement. In the absence of buoyant forces, one requirement for this balance is maintenance of the yield strength of the cement greater than the yield strength of the mud multiplied by the maximum distance from the casing to the wall of the borehole and divided by the minimum distance. If the yield strength of the cement is below this value, bypassing of mud cannot be prevented unless buoyant forces or motion of the casing significantly aid the displacement. INTRODUCTION Successful primary cementing leaves no continuous channels of mud capable of flow during well treatment and production. Prevention of channels requires care. Tep-litz and Hassebroek provide evidence of channels of mud after primary cementing in the field.&apos; Channeling of cement through mud in laboratory experiments has also been reported.&apos;-&apos; Recommendations for improving the displacement of mud include (1) centralizing the casing in the borehole,&apos;-" 2) attaching centralizers and scratchers to the casing and moving it during displacement,18 "3) thinning the isolating the cement by plugs while it is circulated down the casing,%( (5 establishing turbulence in the cement," and (6) holding the cement slurry at least 2 lb/gal heavier than the mud and circulating the cement slurry at a very low rate of flow.&apos; Although much has been written about the above parameters, the relative importance of each has not been well defined. In this investigation, the mechanics of mud displacement are described through results from analytical models and experiments. The model chosen — a single string of casing eccentric in a round, smooth-walled, impermeable borehole — is analagous to casing centralized in a borehole which is not round and to placing more than one string of casing in a borehole. In each, some paths for flow are more restricted than others. A fluid flowing in the borehole may seek the least restricted, or most open, path. This tendency for uneven flow can lead to channeling of cement through mud unless preventive measures are taken. The analytical models describe channeling and give means of balancing the flow. Experimental data test the analytical models and illustrate effects of motion of the casing, differences in density and mud&apos;s tendency to gel. Results are encouraging. Piston-like displacement of mud by an equal density cement slurry is possible through proper balance of the flow properties of the mud and cement slurries to the eccentricity of the annulus. The more eccentric the annulus, the thicker must be the cement relative to the mud. If proper balance is not achieved. bypassing of mud by cement cannot be prevented without assistance from motion of the casing or buoyant forces. Increasing the rate of flow can help to start all mud flowing but cannot prevent channeling of cement through slower moving mud in an eccentric annulus. Thinning the cement slurry tends to increase channeling although the extent of turbulence in the annulus may be increased. Description of flow in an eccentric annulus begins in the next section. It is assumed that (1) the casing is eccentric and is stationary, (2) the mud and cement slurries have the same density and (3) the gel structure of the mud has been broken and the mud and cement follow the Bingham flow model. Effects related to these restrictions will be discussed. FLOW PATTERNS SlNGLE FLUID IN ANNULUS Flow of a single fluid through an eccentric annulus is illustrated in Fig. 1. Part A shows laminar flow of a Newtonian fluid. This distribution of flow was calculated by Piercy, Hooper and Winney.&apos; In fully developed turbulent flow, the velocity distribution around the annulus is less distorted, but the flow still favors the widest part of the annulus Parts B, C and D of Fig. 1 are a qualitative representation of the flow of a Bingham fluid. The yield strength of the fluid increases the severity of bypassing compared to Newtonian flow. At a very low rate of flow, all flow is confined to that portion of the annulus which has the minimum perimeter-to-area ratio. The fluid shears on the perimeter of that area when the pressure gradient multiplied by the area just exceeds the yield stress of the fluid multiplied by the perimeter. Whether or not the minimum perimeter-to-area region encompasses all of the annulus or only a part (as shown in Part B) depends on the geometry of the annulus. If only a part begins to flow, increasing the rate of flow increases the area flowing until finally there is flow throughout the annulus.

By R. D. Daniels, T. G. Oakwood

A study was made of the effects of small quantities of hydrogen on the mechanical properties of colum-bium. Tensile specimens, hydrogenated to concentrations of 20 to 200 ppm, were tested at temperatures of 300°, 191°, and 77°K. Although hydrogen was found to have little effect on the strength of columbium, the ductility of Cb-H alloys was found to be quite sensitive to both hydrogen concentration and temperature. At 300°K, an abrupt loss in ductility occurred at a critical hydrogen concentration, although some ductility was observed beyond the tolerance limit. A similar result was found at a lower hydrogen concentration at 191°K. At 77°K, however, a more gradual loss in ductility with increasing hydrogen concentration was observed. Hydrogenated columbium was thus observed to undergo a ductile-brittle-ductile transition. Metallographic examination of fractured specimens revealed extensive porosity at both 77° and300°K which was a distinct function of hydrogen content. At 191°K, although some secondary cracking was noted, the amount of observed porosity was minimal. These observations are interpreted in terms of hydrogen solubility and mobility as a function of temperature and in the role of hydrogen in promoting growth of microcracks. lHE effect of hydrogen on the mechanical properties of the refractory metals is not, at present, completely understood. A number of studies have shown these materials to be susceptible to hydrogen embrittlement. Roberts and Rogers1 have found that vanadium can be embrittled by hydrogen. It was further demonstrated that fracture undergoes a ductile-brittle-ductile transition as the temperature is lowered from 150° to -196°C; i.e., there is a ductility minimum observed at a certain temperature. The ductility is increased by either raising or lowering the temperature from this point. A more complete study by Eustice and Carlson2 on vanadium containing 10 to 800 ppm placed the ductility minimum at about -100°C with variations reportedly due to hydrogen content and strain rate. Ductility minima have also been found at certain temperatures for tantalum containing 7 ppm H3 and 140 ppm H.4 At hydrogen concentrations above 270 ppm, however, the ductility return at low temperatures was considerably reduced.4 In the case of columbium, some disagreement exists in the literature. Eustice and Carlson,5 Wilcox et al.,6 and Imgram et al.4 failed to find a ductility minimum although a composition-dependent ductile-brittle transition was observed. Hydrogen concentrations in these investigations were 20 ppm,5 1 to 30 ppm,6 and 200 to 390 ppm.4 However, Wood and Daniels7 observed a rather pronounced ductility minimum at hydrogen contents ranging from 19 to 252 ppm. Those theories of hydrogen embrittlement involving the precipitation of diatomic hydrogen which have been applies to ferrous metals8-12 do not seem to be applicable to the case of columbium and other exothermic occluders. Such theories propose that extensive crack formation and propagation occurs by the precipitation and expansion of diatomic hydrogen at internal voids and microcracks. However, photomicrographs of hydrogenated columbium do not show any evidence of damage introduced by the sorption and precipitation of diatomic hydrogen; rather, at high hydrogen concentrations, a hydrogen-rich second phase is precipitated.13&apos;14 In addition, a number of these theories require the development of high hydrogen pressures at voids in the structure.8&apos;10&apos;12 This does not appear to be feasible in the concentration ranges discussed in the aforementioned paragraphs. The possible interaction of atomic hydrogen with microcracks resulting from dislocation pile-ups15,16 remains in doubt since pile-ups have not been observed in bcc metals17 including columbium.18 Wood and Daniels7 have put forth the possibility that a hydride precipitation could be responsible for crack nucleation in columbium. Work by Longson19 has shown that hydrogen embrittlement of columbium parallels the bulk solubility limit; i.e., as the solubility increases, for instance with temperature, the amount of hydrogen necessary to cause embrittlement also increases. Although a hydride precipitation appears attractive as a means of nucleating microcracks in columbium, what require more intensive study are the low-temperature anomalies which have been observed, i.e., the ductile-brittle-d&apos;ictile transition characteristics. Also, the hydrogen concentrations where embrittlement occurs are often below the bulk solubility limits determined by Albrecht et al.13,14 and Walter and Chandler.20 This work is an attempt to determine more definitively the effects of concentration and temperature on the mechanical properties of dilute Cb-H alloys. EXPERIMENTAL PROCEDURE Ultrahigh-purity columbium rods, obtained from the Wah Chang Corp., were cold-reduced by rotary swaging. A chemical analysis is given in Table I. The material was cut into cylindrical blanks 1.50 ±0.005 in. long. Individual specimens were either given a stress relief anneal at 750°C or recrystal-lized at 1200°C. Resulting microstructures were either a "bamboo" structure characteristic of a wrought material or a recrystallized structure with a grain diameter of approximately 100 n. All heat treatments were carried out in a vacuum of 10-5 Torr or less.

Jan 1, 1969

By R. C. Craze

During the past 20 years. research and development in the study of reservoir behavior have dealt principally with flow of oil through sandstones. Many reservoir studies of sand fields have proved valuable in promoting recovery efficiency. This paper discusses fundamental principles governing oil and gas production from sandstone and limestone alike and presents the results of investigations relating to the application of analytical techniques used for sandstone reservoir studies to the study of limestone reservoir performance. The characteristics of limestone porous systems, porosity-permeability relationships, distribution and occurrence of oil, and characteristics of flow through such systems are discussed. Recognition is made of the similarities or differences which these factors exhibit in limestone and sandstone systems. Comparisons between operating data for typical limestone and sand reservoirs are presented. It is indicated that the distribution and movement of fluids in and through porous limestones follow the same fundamental principles underlying such processes in sandstones. This fundamental similarity may readily be discernible in the performance of many limestone reservoirs. The volumetric balance and unsteady state radial flow equation, the fluid displacement equation, use of electrical analogue devices, and other analytical techniques to study the behavior of limestone fields appear fundamentally applicable, but do require thorough understanding of the properties of the formation, of the fluids, their behavior during flow, and adequate production operating data. Need for more complete coring and comprehensive examination of core properties is stressed. The results of "active oil" studies, and of flow and interference tests are presented. Well spacing, well completion, and efficient rates of production in limestone reservoirs are briefly discussed. INTRODUCTION Limestone and dolomite reservoirs constitute the largest source of supply of crude oil in the world. an estimated 60 per cent of present production coming from carbonate reservoirs. In many large geologic provinces such as Mexico. the Middle East, and more recently Canada, almost all the oil is found in this type of rock. In the United States, all of the major oil-producing areas except California and Pennsylvania contain oil-bearing carbonate formations. The discovery in recent years of large oil reserves in the Silurian, Devonian, and Ordo-vician formations in West Texas, in addition to the large reserves in the Permian, has accentuated the interest of operators, geologists, and engineers in limestone formations and in the many problems associated with understanding the performance of these reservoirs. The rapid increase in discovery of oil in limestone formations and the present-day position of prominence held by these fields in the production and reserve picture in all parts of the world emphasize the horizons opened to the reservoir technologist in the field of geological and production research. Pertinent to an interpretation of the behavior of limestone reservoirs are the methods of analysis which may be utilized and a possession of full knowledge of the many factors which influence the analytical procedures. During the past 20 years a well-developed science of reservoir engineering has been built upon the research of many workers who studied the fundamental nature of oil reservoirs, characteristics of the porous media, properties and behavior of the contained fluids, and the mechanics of flow. Application of these studies to production practice has resulted in greater recoveries and more efficient field operation. The major portion of this evolutionary process has been founded upon studies of sand fields. The applicability of these more thoroughly developed techniques for studying sand fields to the study of the behavior of limestone fields becomes a factor of technical and practical significance. In the light of the technological background available to the reservoir analyst, this paper discusses fundamental principles governing oil and gas production from sandstone and limestone alike and presents the results of investigations relating to the application of analytical techniques used for sandstone studies to the study of limestone reservoir performance. LIMESTONE RESERVOIR CHARACTERISTICS The characteristics of limestone and sandstone reservoirs are similar in many respects and they both may occur under similar structural conditions. Fundamentally, the distribution and movement of fluids in and through the porous limestone media follow the same basic principles which dictate such processes in sandstones. Herein lies a fundamental similarity, which may readily be discernible in the performance of many limestone reservoirs. In some limestone fields, as in many sand fields, widely varying formation properties and distribution may reveal themselves in deviations in the performance of the reservoir, in the behavior of wells, and in fluid flow through the rock, and make difficult the delineation of reservoir behavior. Only by reservoir studies, core analyses, and coordinated laboratory and field experimentation can the effects of the many influencing factors upon the nature of limestone production be determined. FORMATION CHARACTERISTICS The chief difference between limestone and sandstone, aside from their chemical compositions, is the difference in the geometry and origin of the porous systems in the two kinds of rock. In sandstone the porous system results entirely from the openings among individual sand grains which occur during deposition. The geometry of the openings between the sand

Jan 1, 1950

By P. L. De Bruyn, R. J. Charles

THE transfer of kinetic energy of translation into other forms of energy by impact is a fundamental process in most crushing and grinding operations. During and after the impact process the original source energy may be accounted for in any of the following possible forms: 1) Kinetic energy of translation of both the impacted and impacting objects. 2) Kinetic energy of vibration of the components of the impact system. 3) Potential energy as strain energy of the components of the system or in the form of residual stresses. 4) Heat generated by internal friction during plastic deformation or during damping of elastic waves. 5) New surface energy of fractured materials. At any instant during the impact process only the strain energy of the components of the system can contribute directly to the brittle fracture process. If fracture is the desired result, as in comminution, it would seem advantageous to choose or arrange the conditions of impact so that a maximum amount of the original kinetic energy could be converted to strain energy at some moment during a single impact. The present work deals with determination of these desirable conditions for a simple case of impact and application of the principles involved to general cases of impact. Experimental Method: Longitudinal impact of a rod with a fixed end was chosen as the impact system for investigation. The rod was mounted horizontally and the fixed end was formed by butting one end of the rod against a rigidly mounted steel anvil. The rod, of pyrex glass, was 10 in. long by 1 in. diam with both ends rounded to a 6 in. radius. The rounded ends permitted reproducible impacts on the free end of the rod and assured a symmetrical fixed end. Pyrex was selected as the rod material because of the marked elastic properties of such glass and the similarity of fracture between pyrex and many materials encountered in crushing and grinding operations. The frequency of natural longitudinal oscillation of the rod was 10 kc, and thus simple electronic equipment could be used for observation of strain changes occurring in the rod at this frequency. As shown in Fig. 1, impacts on the free end of the rod were obtained either by a pendulum device or by a spring-loaded gun. Relatively heavy hammers (100 to 600 g) of mild steel were used in the pendu- lum impacts, while fairly light projectiles (20 to 80 g) were fired from the spring-loaded gun. One of the main objects of the experimental work was to obtain the strain-time history of the rod as a function of the mass and kinetic energy of the impacting hammers. For this purpose a technique involving wire resistance strain gages and a recording oscilloscope was employed. Five gages were applied at equidistant sections along the rod, and by means of a switching arrangement the strain-time history at any section, and for any impact, could be obtained in the form of an oscillograph with a time base. The equation relating strain and voltage change across a strain gage through which a constant current is flowing is as follows: e = ?v/iRF [1] ? = strain, ?v = voltage change, i = gage current, R = gage resistance, and F = gage factor (from manufacturer&apos;s data — SRA type, Baldwin Lima Corp.). With the above equation an oscillograph depicting voltage change vs time on a single trace can be converted directly to a strain-time diagram if a calibration of the vertical response on the oscilloscope screen for specific voltage inputs is available. In the present case the calibration was obtained by photographing precisely known audio frequency voltages on the same oscillograph as that on which a voltage-time trace from a strain gage had been made. Synchronization of the beginning of the single trace with the beginning of the impact was accomplished by permitting contact of the impacting objects to close an electrical circuit from which a voltage pulse, sufficient to initiate the trace, was obtained. The struck end of the rod was lightly silvered for purposes of electrical conduction so that it would form one of the electrical contacts. Markers every 100 micro-seconds on the traces served for a time base calibration. Determinations of the kinetic energies of translation prior to impact were made in the case of the pendulum hammers by measuring the height of fall of the hammer and in the case of the projectiles by measuring the exit velocity from the gun barrel by means of an electrical circuit employing light sources, slits, and phototubes.&apos; During the experimental work it became evident that the time of contact between the impacting object and the rod was an important variable in the impact process. Measurements of the times of contact were made, therefore, for every impact for which a strain-time record was obtained. The time of contact was determined by permitting the impacting components, when in contact, to act as a closed switch and discharge a condenser at relatively constant voltage. The discharge was observed and photographed with a time base on the oscilloscope screen.

Jan 1, 1957

By S. F. Reiter

The paper presents isothermal recrystallization curves for 0.08 and 0.15 pct C steel at subcritical temperatures following small amounts of plastic deformation. The effects of deformation, temperature, and aging on nucleation and growth rates ore described. The free energy of activation for grain boundary migration in steel is given. SEVERAL excellent reviews of the literature have appeared concerning the recrystallization of metals.&apos;-&apos; The present investigation follows the approach advanced by Mehl, Stanley, and Anderson,6-7 in which the rate of recrystallization was analyzed in terms of N, the rate of nucleation, and G, the rate of growth of recrystallization nuclei. Two lots of low carbon, capped steel of the analysis given in Table I were studied. Each lot consisted of a 150 lb coil which had been hot rolled to 0.083 in. and then cold rolled to 0.042 in. at the mill. Strips 0.930 in. wide were sheared perpendicular to the rolling direction. Both steels were normalized before studying their recrystallization characteristics. The strips were cleaned, painted with a magnesia-acetone paste, and made into packs of equal weight, wrapped in 0.002 in. copper foil. The packs were placed in a salt bath at 900°C for 30 min and air cooled. A relief anneal followed in a second salt bath for 15 min at 650°C. The relief anneal was found necessary from early tests in which a longer incubation period and slower rate of recrystallization were observed in relief-annealed lot A steel than in similar material which was strained and recrystallized directly after being normalized. This effect, which indicates the presence of transformation and/or cooling stresses in steel air cooled from above the A, temperature, has also been observed by Samuels8 and Masing.9 Figs. 1 and 2 show the microstructure of lot A and B materials and illustrate the rather uniform No. 8 ASTM grain size produced by this heat treatment. Winlock and Leiter10 observed that strip specimens which had their sharp edges removed elongated more uniformly than those which were not polished. Similarly, when the sheared edges were removed on a belt grinder, it was found in the present investigation that such samples recrystallized more uniformly than did unpolished strips. Therefore, all strips were carefully rounded prior to their extension. The approximate strain limits for the production of large recrystallized grains are from 6 to 12 pct extension." It was found that for the purpose of this investigation, 8 and 9 pct elongation were suitable deformations. The strain rate employed was 0.01 in. per in. per min and produced a yield point elongation of 4 pct. Winlock and Leiter found that mild steel of No. 8 ASTM grain size gave the same yield point elongation when extended at 0.012 in. per in. per min. All of the lot A and B strips extended in tension developed a straight, stretcher strain line at each grip when the upper yield point was reached. The lines were parallel and made an angle of 55" with the edge of the strip. They approached each other with increasing strain and met near the center of the sample at the end of the yield point elongation. Immediately thereafter, a small drop in load was observed and then the load increased in a regular manner with increasing extension. The grips were initially 8 in. apart. After extension, the 6 in. gage length was carefully cut into 1 in. samples. The remainder of the strip was discarded. After a flash pickle in hot 50-50 hydrochloric acid, six samples, each of which had been taken from a different strip, were placed in a basket and submerged in a lead pot for isothermal recrystallization. Although no recovery effect was observed, strain aging did occur after extension. Therefore, samples were always recrystallized within 24 hr after their cold deformation. After recrystallization, the samples were etched with a solution comprised of one part by volume of nitric acid with three parts of water. Bromide printing paper was exposed directly at low magnifications and later used with a mask to measure the desired quantities. First, the average diameter of the largest grain visible in each sample was determined using dividers. Next, the number of recrystallized grains per unit area was counted and recorded as n. Then, for each sample, the combined area of the recrystallized grains was measured by transcribing the grain outlines to standard graph paper. Many determinations of the area of the recrystallized grains were repeated five times and indicated a standard error that was not greater than 25 pct. The average area for six samples was divided by the area of the mask to yield the percentage recrystallized. Recrystallization of 0.08 Pct C Steel The progress of recrystallization at 670°C after 8 pct elongation of lot A steel is shown in Fig. 3, a through f. The shapes of the growing crystals are approximately equiaxed, as is assumed in the

Jan 1, 1953