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By A. D. Zunkel, A. H. Larson

Equilibrium antimony contents of pb-sb alloys in contact with PbO-Sb2O3 slags containing less than 45 mole pct Sb203 uleve determined at 650', 700°, and 750°C in an inert atmosphere. In this ten~pevature range, the antimony contmzt of the alloy increased with increasing temperature at all slag compositions. The PbO-Sb203 phase diagram below 28 mole pct Sb2O3 was determined by thermal analysis and by application of a log sbZ4/y$b0 us plot determined from the equilibrium-activity data. The resulting phase diagram showed a eutectic at a temperature of 604°C and a comfiosition of 21.6 mole pct Sb2O, with a maximum terminal solid solubility of Sb203 in PbO of 5.6 mole pct. These results are compared with existing data in the literature. In the past three decades, only a small amount of experimental work has been done on the slag-metal equilibria in the Pb-PbO-SbaO3 or the analogous arsenic and tin systems. These systems are important in commercial lead-refining processes such as softening and dross fuming since it is impurities such as antimony, arsenic, and tin in lead bullion and Sb2O3, As2O3, and SnOz in lead drosses which must be re-

Jan 1, 1968

By A. H. Grobe, F. N. Rhines

AT elevated temperatures the oxide of silver is unstable in the air at atmospheric pressure, consequently no external oxide scale forms upon pure silver under conditions of high-temperature annealing. When small quantities of certain alloying elements are present in the silver, the formation of a thin external scale is possible' and in addition there may form a subscale composed of the oxide of the solute element precipitated within the body of the silver. Norbury2 and Leroux and Raub3 have reported internal oxidation (subscale forma¬tion) in alloys of silver with 2, 7.5, and 30 per cent of copper. The presence of the subscale is believed to be responsible, at least in part, for the objectionable "fire mark" in Sterling silver.4 Several other alloys of silver, after oxidizing heat-treatments, are known to exhibit undesirable polishing characteristics that may be the result of internal oxidation. Except for the absence of an external scale of silver oxide, it is to be anticipated that silver alloys will prove to be very similar in their oxidation behavior to the alloys of copper, the oxidation characteristics of which have been studied in some detail5,6 The present research confirms this anticipation. The oxidation of a series of 20 dilute alloys of silver has been studied metallographically; some types of subscale not encountered among the copper alloys have been found. Instances of internal oxidation in alloys of most of the metals of the I-b and VIII groups of the periodic system are on record, but evidence of this type of oxidation in alloys of the metals of the intermediate groups is lacking. A number of the metals of the intermediate group, among them cadmium, lead, tin, and zinc, appear to provide the conditions essential to subscale formation; i.e., they form oxides with a relatively low negative free energy of formation, they dissolve other metals that form more stable oxides, and, presumably, oxygen will diffuse through them. In a study of 4o alloys of these white metals only a few cases of internal oxidation have been found. The probable reasons for this difference in behavior will be discussed presently. EXPERIMENTAL PROCEDURE Silver.-The silver alloys employed in the oxidation studies were prepared in heats of 30 grams each from high-purity silver (99.993 per cent Ag)* and the purest avail-

Jan 1, 1942

By Robert T. Hill

PHYSIOGRAPHICALLY, Mexico provinces, which are, in a manner, distinct economic areas. These may be denominated, (1) the Gulf coastal plain; (2) the Cordilleran plateau; (3) the Sonoran, and (4) the Tehuantepecan province. Fig. 1 shows the approximate boundaries of these provinces. The first is the continuation of the coastal plain of Texas and the Gulf region in general, which, except for prospective oil and lignite, has little of interest for the mining engineer.

Jan 1, 1902

By R. T. Keyes, R. B. Clay, L. L. Udy, V. O. Cook, M. A. Cook

Based on compressibility and stress wave velocity in rock, initial explosive loading conditions, the thermochemistry of the explosive and reasonable description of the pressure-distance relations behind the shock front, the distribution of energy between the products of detonation and the burden are estimated as a function of time for various loading conditions. These include 'powder factor', loading density A (fraction of borehole occupied by explosive), and the explosive itself. Factors responsible for rock fragmentation are discussed in terms of: 1) 'release wave fracturing', 2) 'shear wave fracturing', and 3) 'release of loading fracturing' or 'rock bursting'. Release wave fracturing appears to occur only in the immediate vicinity of free faces, and shear wave fracturing only adjacent to the borehole under normal blasting conditions. Rock bursting is thus considered to be the most important means of rock fracturing in blasting. Means for maximizing it are considered. The most important factors to consider include maximum available energy A, explosive density p1, loading density A and 'powder factor'. Maximum efficiency is attained in general by maximizing the A . p1 product. This is achieved by using high density explosives at a loading density of unity (A = 1.0). Ways for achieving this condition are discussed. The bulk-handled aluminized slurry blasting agents have the desired properties for achieving optimum conditions for high blasting efficiency based on the theory outlined herein. Factors considered most important in the blasting of rock are: 1) The maximum available energy A, determined by the heat of explosion Q and the mechanical efficiency ?, a factor intimately associated with the mode of application (A = Q at highest gas concentrations). 2) The 'borehole pressure', pb, or the maximum pressure developed in the borehole after passage of the detonation wave and before the burden has had time to move or become compressed appreciably. (Owing to the short duration of the detonation wave at any particular point in the borehole, the fact that the explosive may not always fill the borehole completely and the further fact that the burden may not actually see the detonation pressure, the borehole pressure is considered more significant than the detonation pressure p2 as a performance factor in borehole blasting.) The borehole pressure is determined by the explosion or adiabatic pressure, p3 , and the loading density, A, or the fraction of the borehole filled by explosive. 3) The physical conditions important in the application of the explosive are: a) The 'powder factor,' (We/Wr), or the ratio of the wt of the explosive to that of the rock being blasted expressed as lb per ton or more generally in lb/cu yd. b) The bulk density, p1 ?. c) The 'burden' or 'line of least resistance,' the spacing between boreholes, the geometry of the borehole pattern and sequence of firing. d) The physical and chemical properties of the rock, most significant of which are possible heterogeneties, such as faulting, prefracture, and greater than micro-scale chemical heterogeneities. (This factor is not considered here but deserves a great deal of careful consideration.) All of these factors need to be carefully considered in the most economical engineering of a blast. Here is considered firstly an outline of the present status of dynamic rock mechanics, particularly as it pertains to blasting. The factors pertaining to the most efficient application of blasting agents are also considered, followed by a discussion of methods of application to achieve optimum explosives performance. ROCK MECHANICS Dynamic rock mechanics is currently a rapidly developing science contributing greatly to a better understanding and consequently the more effective application of explosives in blasting of rock.1-22 Basic to the development of the science of dynamic rock mechanics were the advances of Goransen23 and the Los Alamos and NOL groups24-28 concerning rock and stress wave phenomena and the transmission and reflection characteristics of stress waves at interfaces between different media. Basing considerations on this new knowledge as well as new experimental methods of study (ultra-high speed streak and framing cameras and electronic timers) the theory of fracture and failure of solids under impulsive loading by stress waves developed rapidly.14,16,27-29 Also the

Jan 1, 1967

[Trans. No. Place Date Vol. Page 1. Wilkes-Barre, Pa.*.. *May: '71.. 1 3 2. Bethlehem, Pa Aug. '71.. 1 10 3. Troy, N. I X Nov. '71.. 1 13 4. Philadelphia, Pa Feb. '72.. 1 17 5. New York, N. Y.*.... May, '72.. 1 20 6. Pittsburgh, Pa Oct., '72.. 1 . 25 7. Boston, Mass Feb., '73 1 28 8. Philadelphia, Pa.*.... May, '73 2 3 9. Easton, Pa Oct., '73 2 7 10. New York, N. Y Feb., '74.. 2 11] [ ]

Jan 1, 1925

By A. S. Richardson

AIR conditioning, or air cooling, for the improvement of ventilation in the Butte mines has come into increasing use during the past 10 years. In part, the methods practiced have been described in previous publications of the Institute, but some improvements on earlier methods have been made and a number of new features have been developed. This paper is presented as a record of progress made, and for the sake of completeness describes all general features of the work. The need for air conditioning in the ventilation of mines in the district arises from the fact that the temperature of the ground and mine water has shown a very great increase with increase in mining depth, and has now reached a maximum of slightly over 130ºF. The most difficult part of the ventilation problem is the maintenance of temperature and humidity of a satisfactory standard in the working places, especially on the lower levels. Although ordinary ventilation is adequate to maintain good conditions in most of the working places it is subject to a number of limitations at great depth. Most important among these limitations is that with increase in depth the air becomes heated before it reaches the working places, both by compression from increase in atmospheric pressure and by heat transferred to it from rock at high temperature, so that its capacity for lowering temperatures is greatly reduced before it reaches the operating zone. Increasing depth of mining also increases the distance traveled by the air in its passage through the mine, and this causes a corresponding increase in resistance to air flow, so that there is greater difficulty in maintaining even the same volume in circulation. Thus, in the face of a demand that the ventilating system have a very much greater capacity to remove heat from the mine, the tendency is for that capacity to diminish. The only evident alternatives were (I) the opening of additional air shafts to increase the volume of air in circulation, (2) an extension of the existing system that would be subject to the same limitations, or (3) the adoption of an entirely different method such as air cooling. Fortunately for an economic solution of the problem, the mean annual temperature of the surface atmosphere at Butte is about 40°F., with very low relative humidity in summer, so that there is unlimited natural cooling power at a temperature range adaptable to air-conditioning methods. METHODS Two similar methods of air conditioning are used, as necessitated by service requirements and dependent upon the equipment available. In one, which is the more important and has the greater cooling capacity, water is circulated in a closed circuit, and, alternately, first absorbs heat from warm mine air and then dissipates it in the surface atmosphere by cooling at a cooling tower. The second

Jan 1, 1941

By H. L. Hartman

The estimation of the magnitude of pressure changes which occur in mine ventilation circuits is of primary importance to the mining engineer in making changes in an existing mine or in projecting the ventilation requirements of a new mine. It is a formidable task in many cases, because no adequate theory is available and empirical data are unreliable or even lacking. The common practice of increasing one's estimate of the mine static pressure by an arbitrary "safety factor" to compensate for the unknown is a poor substitute for accuracy. Generally little difficulty is encountered in calculating friction losses in mine airways. As long as the friction factor can be reliably estimated, the well-known Atkinson formula gives accurate results. However, it is in the determination of shock losses that the ventilation engineer encounters difficulty and is apt to resort to an arbitrary allowance. Shock losses may constitute as little as five or as much as twenty-five percent or more of the overall pressure drop in the mine, and such allowances are generally completely unsatisfactory. Since other shock losses have been covered by McElroy (1), this paper deals with a long-neglected source of shock and pressure change in ventilation circuits, divergence and convergence of airflows, here referred to by their more common mining terms, splits and junctions. PREVIOUS WORK There is practically no fundamental information available in ventilation literature on the splitting and junction of airflows, either in mining or mechanical engineering periodicals or handbooks. Fluid mechanics textbooks seemingly avoid the subject of divergence and convergence, except for brief empirical treatment. The only investigation reported for mine ventilation systems was by Weeks, et a1 (21), in 1933. Although applicable to the case of line brattices in coal mines, it cannot be applied to the general case of mine splitting and junctions involving change of direction with little or no area change. In dealing briefly with the subject of shock losses at splits and junctions, McElroy (1) suggests only that they be considered comparable to bends, with losses at junctions being increased 50 pct to allow for interference of merging streams. He recognizes the importance of quantity ratio but concludes that exact quantitative data are lacking to compute losses at splits and junctions. A very capable summary and analysis of the state of knowledge in industrial ventilation and fluid mechanics regarding losses due to divergence has recently been reported by Gilman (3). In considering all earlier work dealing with both air and water as fluids, he compares results on a common basis and obtains good empirical agreement. For divergent flow, the controlling variable in each branch is the quantity ratio, although the deflection angle is of secondary importance. Empirical equations are presented for straight and 90-deg branches with varying velocity ratios, assuming branches smaller than the main duct. These formulas are modifications of the Borda equation for abrupt contraction and expansion. The only information available on shock losses in convergent flow are approximate experimental data presented by Alden (4) and the Manual of Recommended Practice for Industrial Ventilation of the American Conference of Governmental Industrial Hygienists. Alden considers the effects of both quantity ratio and deflection angle. The data indicate an effect opposite to that observed in divergence, the shock loss varying directly with quantity ratio. SHOCK LOSS THEORY Because pressure losses due to shock have been found to bear a constant relation to the mean velocity of flow in a given conduit, they are frequently expressed as a dimensionless function of the velocity head, termed the shock loss factor. For airflow in ducts and mine airways, the shock loss may be represented by the formula (1): Hx - XHv, (1)

Jan 1, 1961

By D. Beregekoff

In the routine examination of a wide variety of metal specimens it is sometimes necessary to have special methods of polishing in order to retain and reveal certain details in each specimen. Among such special cases is the retention of graphite in malleable and gray cast irons, the preservation of all types of nonmetallic inclusions in both hard and soft steels, obtaining a scratch-free surface with soft metals, and avoiding the usual relief effects with very hard specimens such as tool metals con-taining various carbide and nitride phases. It is the purpose of this paper to give an account of some of these special polishing methods in use at the Union Carbide and Carbon Research Laboratories. The polishing procedures outlined have been found to give uniform results. It is obvious that only general rules and the most important working details can be given here. Following these rules, the polisher can obtain satisfactory results if he possesses the necessary patience and has a sincere desire to give as nearly perfect a finish as possible to his work.

Jan 1, 1939

By G. W. Cullen

Niobium-tin has been prepared on insulating suhstrates hby simultaneous hydrogen reduction of gaseous niobium and tin halides. Stoichiometric material is greater than 98.8pct theoretical density, appears to he single-phase, and has a total impirity level less than 0.3 at. pct. Transition temperatures and lattice constants may he related to composition. Typical current densities in various fields and orientations are given. IT is known that Nb3Sn carries large current densities in high fields, 1 and exhibits an unusually high transition temperature2 and critical field.3 For these reasons high-field solenoids have been constructed of this material.4 Because of the emphasis on solenoid fabrication, much of the materials research has been directed toward development of wire geometries wherein the brittle Nb3Sn is supported by a more malleable metal or alloy. There are, however, basic studies and applications that can be carried out only on Nb3Sn supported by an insulator. Insulating substrates are desirable for a number of reasons: the substrate does not interact with applied or induced currents and fields; diffusion of metallic species into the de- posit is avoided, both during the preparation and during subsequent heat treatment; irradiated samples are not more active than the deposit itself. Unsupported Nb3Sn geometries may also be prepared by preferential chemical dissolution of the insulating substrate. This report describes the preparation and properties of Nb3Sn deposits on ceramic substrates. Experiments currently utilizing material prepared in the manner described in this report include the following: dependence of current-carrying properties on field strength and orientation 5,6 radiation damage,7,8 tunneling,9 thermal conductivity (substrate removed),1° microwave surface impedance," tube magnetization,6,12 resistivity as a function of temperature,13 and current density and transition temperature as a function of annealing.14 Possible practical applications include magnetic shielding, superconductor generators, and frictionless bearings. PREPARATION Methods for the deposition of elemental niobium and tin by hydrogen reduction of the gaseous metal halides have been known for some time,15,18 but only recently a procedure was developed in this laboratory17 for the codeposition of these two metals on a hotwire as the intermetallic compound, Nb3Sn. This method of simultaneous hydrogen reduction of the gaseous niobium and tin chlorides is used for the preparation of Nb3Sn On ceramic substrates. The procedure differs from that employed on a hot wire in that insulating substrates cannot conveniently be heated to temperatures greater than their surround-

Jan 1, 1964

By H. A. Schwartz

FROM time to time, one of the authors has had occasion to investigate the graphitizing reaction and has published the results mainly as discussion1 of the work of other investigators. In view, therefore, of the diversity of both observations and interpretation, it seemed well to attempt a revision of the entire subject in the Research Laboratory of the National Malleable Castings Co. The work consisted of a careful study of a single, impure, iron-carbon alloy. The material, which may be considered typical low-carbon white cast iron of the malleable industry, was an air-furnace iron of the following composition: carbon 2.30 per cent., silicon 1.20 per cent., manganese 0.29 per cent., phosphorus 0.156 per cent., sulfur 0.048 per cent. The freezing range extended from 1213° to 1132° C., the latter figure agreeing with Gontermann's data .2 We have attempted to define the equilibrium diagram of this alloy, in the stable condition as related to the metastable diagram, from a temperature somewhat below the eutectic freezing point to a temperature below Ar1 and for a graphitic-carbon content from practically nothing to the original total carbon of the specimen (see Fig. 6). More especially we desired to locate the line in the stable diagram corresponding to the Acm line of the metastable system, which is designated by analogy, the Atm line (tm from temper carbon) ; also to determine the location of Aim with respect to Acm toward their lower extremities at Ar1 in order to determine whether or not graphitization is completed by the separation of an iron-carbon eutectoid analagous to pearlite in the iron-cementite system. This would involve further a comparison of the locations of the stable and metastable A1 points.

Jan 8, 1922

By A. J. Strauss

The solubilily of lead in PbS as a funclion of lemperature has been investigated by means of Hall coej'icient (RH) measurentents OIL samples prepared by annealing and quenching Bridgman-grourz single crystals, which contain excess lead incorporated during /heir growth from the mell. For sufficiently long annealing times and sufficiently rapid quench rules, the samples obtained consist of n-lybe PbS snturated with In the semiconducting compounds PbS, PbSe, and PbTe, the point defects associated with the presence of lead in excess of the stoichio metric composition are shallow donors. The defects associated with the presence of excess nonmetal are shallow acceptors. lead at the annealing teuiperatiire, together luilh a dispersed second phase of lead microprecipitates. Due to the retrograde solubility of lead, the measured free carrier concentration (n = l/eR77) decreases with decreasing annealing tewperature (T) from- 2.4 X 10 em-3 for 1l85OK to 1.3 X 1018 cm-3 for 623°K. The dala are well-represented by the equation n =(1.08 x 102) exp[ - (0.37 ev.)/kT] cm-3 For most undoped samples of these compounds, the carrier concentration at room temperature and below is determined primarily by the stoichiometry, since the concentration of either excess lead or excess non-metal is large compared to the concentrations of intrinsic carriers and electrically active impurities. Therefore the dependence of composition in temperature and partial pressure can be investigated by means of Hall coefficient measurements, even though the deviations from stoichiometry do not exceed 0.03 at. Pct

Jan 1, 1968

By O. W. Simmons, L. W. Eastwood, C. M. Craighead

The results of a preliminary study of 113 ternary titanium-base alloys are described. The compositions investigated were as follows: 1. Ternary titanium-carbon alloys containing copper, silicon, vanadium, chromium, manganese, iron, or cobalt. 2. Ternary titanium-nitrogen alloys containing chromium. 3. Ternary titanium-chromium alloys containing additions of vanadium, molybdenum, tungsten, cobalt, or nickel. 4. Ternary titanium-manganese alloys containing additions of silicon, chromium, tungsten, or iron. Tensile properties, minimum bend radii, hardnesses, response to heat treatment and aging treatment, and phase relationships for these alloys were determined. THIS is the second in a series of papers describing some of the results of the exploratory work on titanium alloys being conducted at Battelle Memorial Institute for the Wright-Patterson Air Force Base. The work with the binary alloy systems has been described in a previous publication.' This paper describes ternary titanium-base alloys as follows: 1. Ternary titanium-carbon alloys containing copper, silicon, vanadium, chromium, manganese, iron, or cobalt. 2. Ternary titanium-nitrogen alloys containing chromium. 3. Ternary titanium-chromium alloys containing additions of vanadium, molybdenum, tungsten, cobalt, or nickel. 4. Ternary titanium-manganese alloys containing additions of silicon, chromium, tungsten, or iron. As the preparation and fabrication of the 0.5-Ib experimental titanium alloy ingots to 14-ga sheet, as well as the methods of testing used in this work, have been described in the first paper of this series, Titanium Binary Alloys, no further discussion of these techniques will be given. Ternary Alloys Containing Carbon The following alloys of titanium, containing carbon and one other metal, were investigated: 1. 0.25 pct carbon; 1, 2.5, and 5 pct copper. 2. 0.25 pct carbon; 1, 2, and 3 pct silicon. 3. 0.25 pct carbon; 1, 2.5, and 5 pct vanadium. 4. 0.25 pct carbon; 2.5, 3.5, 5, 10, and 15 pct chromium. 5. 0.5 pct carbon; 2.5, 3.5, and 5 pct chromium. 6. 0.25 pct carbon; 1, 1.75, 2.5, 3.5, 5, 7.5, and 10 pct manganese. 7. 0.5 pct carbon; 1.75, 2.5, 3.5, 5, 7.5, and 10 pct manganese. 8. 0.25 pct carbon; 0.25, 0.5, 1, and 2 pct iron. 9. 0.25 pct carbon; 1, 2, and 3 pct cobalt.

Jan 1, 1951

By James B. Duke, Ernest W. Greene

An idea of what is meant by "Ultrafine Minerals Or Slimes" as used in the title can be had by an examination of Fig. I. Particle size distributions are presented for a crude kaolin clay, a coarse fraction and a fine fraction. The crude kaolin as mined was blunged with water, degritted through a 325-mesh Tyler screen, and dispersed with sodium silicate. The dispersed crude was then centrifuged in the laboratory into the coarse and fine fractions shown in the figure. The distribution curves were obtained by the well known sedimentation technique of Casagrande' using a long arm centrifuge to obtain equivalent spherical diameters down to 0.2 microns on the finer fraction. Fig. 1 shows the coarse fraction kaolin to be 50% finer than 3 microns, while the crude kaolin is 50% finer than 1.4 microns, and the fine fraction 50% finer than 0.6 microns. For comparison 53 microns on the horizontal scale would represent Stokesian diameters which would just pass a 325- mesh Tyler screen, taking into consideration the Andreasen sieve correction factor of 1.22 X the screen opening.' Another helpful comparison is the surface areas, which in square meters per gram, are 0.044 for 53 micron particles, 0.77 for 3 microns, 1.65 for 1.4 microns, and 5.0 for 0.46 micron particles. Fig. 2 is an electron micrograph of a similar fine fraction kaolin showing the hexagonal plate- like particle shapes.

Jan 10, 1962

By R. L. Jones, H. Conrad

The effects of gain size on the room-temperature tensile properties of commercial(A- 70)-purity and iodide-purity titanium were investigated by concurrent tensile testing and thin-foil electron transmission studies. The mechanical tests showed that the effect of grain size on the yield, flow, and fracture stresses could be expressed by relations of the Hall-Petch type. The magnitude of the grain size effect on the yield stress was larger for commercial-purity than for high-purity titanium, but in both materials it was intermediate between that typically observed for fcc and for bcc metals. The effect of strain on the gain size sensitivity of the flow stress was found to reflect the grain size dependence of strain hardening. The electron transmission study indicated that the tensile behavior could be accounted for in terms of the dislocation densities and distributions formed during deformation. It was concluded that the effect of grain size on strength could be attributed to a relationship between grain size and the dislocation densities generated in initiating and sustaining plastic flow, the difference in stress levels being due to strain hardening. The relationships between recrystallized grain size, uniaxial tensile properties, and dislocation substructure have not been explored in any detail for a titanium. With titanium and its alloys finding increasing applications in aerospace systems, such information has become essential. The research described in this paper had two objectives: first, to document the effect of grain size on the yield, flow, and fracture stresses of unalloyed a titanium by the tensile testing of recrystalliied specimens at room temperature; second, to attempt an interpretation of the mechanical test behavior in terms of the dislocation structures formed on deformation, as observed by transmission electron microscopy of thin foils prepared from deformed tensile specimens. The observations reported here are restricted to room-temperature deformation; the effect of temperature on the yield and flow stresses of a titanium and the athermal nature of the contribution of grain size to the flow stress have been discussed elsewhere.1"3 EXPERIMENTAL DETAILS Two purity grades of unalloyed titanium have been investigated: Crucible Steel A-70, a typical commer- cial-purity product, and a high-purity iodide grade supplied by the Foote Mineral Co. Chemical analyses for interstitial impurity contents are given in Table I, together with values for the total interstitial atom fractions in terms of oxygen equivalents, which were calculated by the method outlined previously.4 ,5 According to the manufacturer's nominal analysis, the A-70 grade also contains about 3700 ppm of Fe. The A-70 grade was supplied as 1/4-in.-diam centerless-ground rod. The iodide grade was supplied as crystal bar which was consolidated to approximately 1/4-in.-diam rod by a single, rapid, molten zone pass, using electron beam heating. The 1/4-in. rods were cold-swaged to 0.078-in.-diam wires and 2-in. lengths were recrystallized in a vacuum of -5 x 10-5 torr, giving grain sizes in the range 0.8 to 30 . The thermal treatments and resulting grain sizes are summarized in Table 11. Since there was in no case any obvious sign of a bimodal dis tribution of grain sizes, the grain size values quoted in Table I1 are those obtained from mean linear intercept measurements involving >I00 grains. For the two coarse grain sizes the measurements were made using conventional optical techniques. It was noted during these determinations that the etchants used (10 pct HF; 30 pct HN03; 60 pct H20 and 2 pct HF; 2 pct H202; 96 pct H20 were both tried) etched grain boundaries very nonuniformly and optical polarization effects had to be employed to reveal boundaries which might otherwise have been missed. It was found that this problem became more acute with the finer grain sizes as the usefulness of polarization diminished.

Jan 1, 1970

By William Fink

NICKEL is used as an alloying element in several complex commercial aluminum alloys, among which are found some very interesting proper-ties, such as relatively high strength at elevated temperatures, relatively low coefficient of expansion, the absence of permanent growth, ability to take a good polish, and a bright, pleasing as-cast surface. For that reason the aluminum-nickel system was included in the list of binary aluminum systems that are being studied as a preparation for the investigation of more complex commercial alloys. This paper is the fifteenth of a series from the Research Laboratories of the Aluminum Company of America reporting the results of investiga-tions of equilibrium relations in aluminum-base alloys of high purity. The aluminum-nickel equilibrium diagram from 0 to 18 per cent nickel was determined, using the purest material available.

Jan 1, 1934

By E. S. Fisher

GRAIN coarsening implies a discontinuous type of grain growth during which a few grains in a fine grained recrystallized matrix grow to large grain sizes at the expense of the matrix. Studies of this phenomenon in various metals1,2 indicate that grain coarsening may result when continuous grain growth in a fine grained matrix is inhibited by either a dispersion of very fine inclusions or by a strong texture. In the former case a period of annealing time exists prior to grain coarsening during which grain growth inhibition is gradually de- creased by dissolution or coalescence of the dispersed inclusions. This mechanism can be made to occur in uranium during anneals at high a phase temperatures. ' A study of some of the factors influencing the kinetics of grain coarsening and the coarse grain sizes in a uranium has led to a method for preparing a uranium single crystals. Previously such single crystals containing considerable substructure were prepared at this laboratory by a phase change method, similar to that described by Cahn.3 Attempts to prepare more perfect single crystals by strain-anneal techniques were unsuccessful. Cahn3- as reported his attempts to apply such techniques to uranium. He proposed that the failure of strain-anneal techniques is basically due to the many twins which

Jan 1, 1958

By W. F. Brace, James D. Byerlee

Although prediction of failure of rocks may be ultimately possible without knowing in detail how failure occurs, understanding of this process is certainly of fundamental interest in rock mechanics. Of the various failure mechanisms, probably brittle fracture is of greatest interest. Recent reviews have brought this subject nearly up to date (Hock,1 Price,2 and Jaeger 3) and here, we summarize certain recent developments. As our understanding of brittle fracture is derived almost solely from laboratory studies this will amount to a review of certain laboratory experiments. New studies in four areas are pertinent; these concern 1) the volume changes which accompany brittle fracture, 2) the propagation of cracks in compression, 3) certain frictional characteristics of rocks and minerals at high pressure, and 4) the law of effective stress for crystalline rocks. Our objective here is less to present an entirely consistent, complete picture of how a rock fractures than it is to emphasize gaps in our understanding and, thus, suggest areas that need further study. Progress is still painfully slow in this field and perhaps this approach will stimulate new work. OBSERVATIONS Although the behavior of large rock masses is most often the concern in rock mechanics, the number of large-scale experimental tests is still vanishingly small. Our experimental observations arc, by and large, still made on small, relatively flaw-free, rock samples. Here also we report the behavior of small samples.

Jan 1, 1967

By F. W. Schroeder

AT the annual meeting of the Institute 2 years ago, a paper,1 " Requirements of Refractories for Open Hearths," was presented by F. W. Davis and G. A. Bole of the U. S. Bureau of Mines. In a brief foreword, D. A. Lyon stated that the paper was not to report the results obtained but rather to present an outline to serve as a basis for discussion. The essential parts of an open-hearth furnace were described and the conditions under which they operate. Some constructive discussion followed the reading of the paper. One of the first fellowship investigations undertaken by the Bureau of Mines in 1924 under the cooperative agreement with Carnegie Institute of Technology, through the Metallurgical Advisory Board, was to determine service conditions of open-hearth refractories. The present paper gives the results of this work which was done in the Pittsburgh district and was in charge of the authors. Material contributions in the form of data were contributed by E. N. Bauer, J. W. Campbell, G. H. Pfeiffer and A. Grodner, Carnegie Institute of Technology research fellows. The study covered 18 mos.

Jan 7, 1926

By J. W. Pugh

PREFERRED orientations in cold-rolled body-centered-cubic metals appear to have remarkable similarity. The as-cold-rolled textures in iron,1,2 silicon-iron,3 mild steel,4 molybdenum, vanadium,&apos; chromium,&apos; tantalum,&apos; tungsten,&apos; and a-zirconium-niobium alloys10 have been determined. These textures have, in some cases, been represented by congrUOUS pole figures and have all been described in one or both of two ways. They have frequently been reported as predominantly (100) <011> orientation

Jan 1, 1959

Occasionally it is interesting, and sometimes useful, to review the past for early references to our industry, and to learn of the trials and travail passed through before it arrived where it now is - and the results of such a review follow. Some time ago one of our modern playwrights and poets, Arthur Guiterman, turned to coal, with the following result : Afar in the Carboniferous time I grew in Paleozoical slime, A lepidodendron with boughs on my stem And lepidostrobusea grew out of them. My roots in the mud of the ages I spread And up to the heavens I vaunted my head, I throve in the heat of tropical sun, And now I am coal at two dollars a ton.

Jan 1, 1935