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By A. R. Elsea, C. C. McBride

HIGH-TEMPERATURE alloys, that is, alloys that are strong at high temperatures, have become increasingly important with the development of modern aircraft engines. Many alloys of this type are available. However, metallurgists do not have a clear understanding of the phases or structures which are responsible for these high-temperature properties. If these basic factors were understood, it might be possible to make better or cheaper alloys for service at high temperatures. For this reason, an investigation of the fundamental factors promoting high-temperature strength in alloys was started at Battelle Memorial Institute. This was to have included a study of the relationship between the structure and properties of cobalt-chromium base alloys of the vitallium type. It soon became clear that the structure of vitallium is quite complex and that the equilibrium diagrams which should explain these structures were unreliable. As a result, the cobalt-chromium binary diagram was determined as the first phase of this investigation1. This diagram is shown in fig. 1. During the study of the cobalt-chromium binary system, it was learned that these alloys may pick up considerable nitrogen when melted and heat treated in air. The extent to which nitrogen affects the various reactions in cobalt-chromium base alloys was not known, but there were indications that this impurity might be responsible for some of the erratic test results obtained for vitallium. Consequently, nitrogen was the first ternary addition studied. Thereafter the work was extended to ternary additions of iron and of nickel. This paper describes the investigation of the effects of nitrogen, iron, and nickel upon the reactions in cobalt-chromium alloys with 80:20 and 68:32 cobalt-chromium ratios. Experimental Work Alloy Preparation: A series of cobalt-chromium base alloys containing various amounts of the third element being studied were made for both the 80:20 and the 68:32 cobalt-chromium ratios. Electrolytic chromium, cobalt, and iron, and reagent-grade nickel powder were used as melting stock. Table I contains the chemical analyses of these materials. The charges were melted in alun-dum thimble crucibles which absorbed chromium oxide and effectively deoxidized the melts. These crucibles were supported by close-fitting graphite sleeves so that if they cracked during melting the metal would not be lost. Carbon increases, during

Jan 1, 1951

By J. S. Pascover, J. K. Abraham

The influence of the early stages of precipitation on the kinetics and structure of martensite formation in Fe-27Ni and Fe-29.5Ni alloys containing from 0 to 10 pct Ti was examined with X-ray and electron microscopy techniques. The formation of a coherent, ordered preprecipitate had a profound stabilizing effect on the austenite. The Ms was decreased by increased titanium content and aging time up to a critical time. When the critical aging time was exceeded, the Ms was observed to increase markedly. The formation of the clusters was insuppressible and the volume fraction of clusters formed during the quench was a function of the titanium content. Martensite resulting from transformation of the clustered austenite is tetragonal with the c/a ratio increasing with titanium content. A model for the tetragonality is suggested. The morphology and substructure of the m artensite is inter-preted in terms of the above information and the cur-rent models of twinned martensite. ThE ramifications of precipitation in austenite to the properties of austenite have been the subject of numerous investigations. The current research is concerned with the influence of precipitation in austenite on the kinetics and structure of subsequent marten-site formation. In a previous investigation, Abraham et al.1 followed the aging reaction in an Fe-29.5Ni-4.2Ti* (at. pct) alloy using an X-ray diffraction technique. This technique, employing a Guinier camera, provided kinetic measurements through observation of the side band position as a function of aging time. The salient results of this work were: 1) The initiation of precipitation was not suppressed by quenching, i.e., there was a finite cluster zone size at zero aging time; and 2) The hardness of the aged austenite correlated extremely well with the zone size. During the previous work it was noted that the mar-tensite formed after aging was tetragonal, substanti-ating an earlier observation.2 Systematic investiga-tion revealed that the martensite was tetragonal in both the solution-treated then quenched, and the solu-tion-treated, aged, and quenched condition, and, furthermore, that a marked stabilization of the austenite occurred as a function of aging time. The present work is concerned with documenting the tetragonality and the stabilization phenomena as well as the ob- served microstruction with a suggested rationale for the behavior noted. EXPERIMENTAL PROCEDURE The compositions of the alloys are listed in Table I. The analyses were performed after the solution treatment of the strip material. Nickel was determined using the standard dimethy1-glyoxime procedure whereas titanium was determined colorimetrically with hydrogen peroxide and volumetrically by titrating with ferric iron. The materials were melted in a 5-lb vacuum induction furnace, cast into 2-in.-diam ingots, and forged in a temperature range of 950. to 1200°C to 1/2-in. slabs. The three higher titanium containing materials cracked during forging; therefore, to get the alloys into strip form, slices 1/8 in. thick were cut from the slab, homogenized 4 hr at 1150°C, then cold-rolled to a 0.04-in. thickness. The remaining slabs were hot-rolled, homogenized 4 hr at 1065"C, then cold-rolled to a final thickness of 0.03 in. All of the heat treatments were performed under a protective atmosphere of argon. The Ms temperature for most of the alloys is below room temperature; therefore, it was possible to solution treat, quench to room temperature, polish, and then observe the transformation optically on a cold-stage microscope. To determine the effect of aus-tenitizing temperature on Ms, eight of the alloys were treated at two temperatures, 1025" and 1120°C. No measurable variations in Ms were noticed. The remaining alloys were treated at 1025°C. The specimens, : by 5/16 by 0.03 in., were austeni-tized in a vertical tube furnace under a dynamic argon atmosphere. The bottom of the tube was submerged in water for quenching purposes. The question of stabilization that may be operating at room temperature was investigated and found to be negligible. Many of the specimens were held at room

Jan 1, 1970

By Earl W. Palmer, Cyril Stanley Smith

StKip of any of the metals used for deep drawing operations occasionally yields cups that are defective because of a rim that varies in height around the cup in a wave-like manner. Some such defects are traceable to tools or other press factors, but when the protuberances formed (usually four in number on brass and other copper alloys) are symmetrically disposed with respect to the rolling direction of the strip, they are invariably attributable to the metal. The effect is known as "earing" and the protuberances are called "ears." Other terms frequently heard are "tips," "scallops," and "corners." It is recognized that the effect is most commonly a result of a directional crystal structure produced by rolling and annealing operations in the manufacture of the metal strip. Numerous papers dealing with various aspects of the earing effect have appeared in the literature, those listed in the references1 being especially interesting and valuable. An investigation of the factors influencing earing of brass cups has been in progress in the laboratories of the American Brass Co. for several years, and it was thought desirable to make some of the results generally available in summarized form. The present paper discusses many factors that do and do not contribute to ear formation. In addition, a section is devoted to methods of minimizing the earing tendency of brass sheet by proper selection of the cold-rolling and annealing schedule by which it is produced. In the space available, it is impossible to quote detailed experimental procedures and numerical results. However, the authors make no statement that they do not believe to be properly substantiated, either by experimental evidence obtained under laboratory conditions or by experience in the actual production of deep-drawing brass in the brass mill. Mechanism of Ear Formation It must be clearly understood that the formation on cups of symmetrical ears, four or more in number, is attributable solely to the strip metal, and results from the strip having different deformation characteristics in different directions. The tools used in the drawing process, or the type and completeness of lubrication of the strip, have nothing to do with the problem of ears, although they do, of course, greatly affect the "drawing quality" of the strip and the general appearance of the cup. A single tip may be drawn up on the rim of a cup because of misalignment of the tools, or because the gauge of metal varies from side to side of the strip. The two-ear form that sometimes appears is also traceable to gauge variations. However, the four-ear and six-ear symmetrical forms that we are concerned with here are caused by factors inherent in the structure of the metal itself.

Jan 1, 1942

By Cyril Stanley Smith, Earl W. Palmer

StKip of any of the metals used for deep drawing operations occasionally yields cups that are defective because of a rim that varies in height around the cup in a wave-like manner. Some such defects are traceable to tools or other press factors, but when the protuberances formed (usually four in number on brass and other copper alloys) are symmetrically disposed with respect to the rolling direction of the strip, they are invariably attributable to the metal. The effect is known as "earing" and the protuberances are called "ears." Other terms frequently heard are "tips," "scallops," and "corners." It is recognized that the effect is most commonly a result of a directional crystal structure produced by rolling and annealing operations in the manufacture of the metal strip. Numerous papers dealing with various aspects of the earing effect have appeared in the literature, those listed in the references1 being especially interesting and valuable. An investigation of the factors influencing earing of brass cups has been in progress in the laboratories of the American Brass Co. for several years, and it was thought desirable to make some of the results generally available in summarized form. The present paper discusses many factors that do and do not contribute to ear formation. In addition, a section is devoted to methods of minimizing the earing tendency of brass sheet by proper selection of the cold-rolling and annealing schedule by which it is produced. In the space available, it is impossible to quote detailed experimental procedures and numerical results. However, the authors make no statement that they do not believe to be properly substantiated, either by experimental evidence obtained under laboratory conditions or by experience in the actual production of deep-drawing brass in the brass mill. Mechanism of Ear Formation It must be clearly understood that the formation on cups of symmetrical ears, four or more in number, is attributable solely to the strip metal, and results from the strip having different deformation characteristics in different directions. The tools used in the drawing process, or the type and completeness of lubrication of the strip, have nothing to do with the problem of ears, although they do, of course, greatly affect the "drawing quality" of the strip and the general appearance of the cup. A single tip may be drawn up on the rim of a cup because of misalignment of the tools, or because the gauge of metal varies from side to side of the strip. The two-ear form that sometimes appears is also traceable to gauge variations. However, the four-ear and six-ear symmetrical forms that we are concerned with here are caused by factors inherent in the structure of the metal itself.

Jan 1, 1942

By W. B. Mather

THE object of this paper is to record and interpret data collected during the examination of over 250 barite deposits in the Central Mineral District of Missouri. [ ] In the course of this study, the origin of the deposits, which the author believes to be hydrothermal, has been given particular attention. Economic barite deposits occur in two main areas in Missouri: (I) in the Washington County District of Southeast Missouri, from which over go pct of the state's production is derived; and (2) in the Central Mineral District, which includes portions of 15 counties in Central Missouri (Fig I). Barite in the smaller Washington County District is mined from widespread low grade, relatively shallow residual deposits, whereas in the Central District, it is mined

Jan 1, 1947

By A. W. Fahrenwald

PRACTICALLY all fine grinding is done in a ball mill or some modification of a ball mill. Millions of tons of material are ground each year. The cost varies from, say, a minimum of 10 c. to a maximum of 35 c. per ton. It is thus obvious that even small improvements, which may result in increased grinding efficiency, would be welcomed by mill operators. A review of literature shows that various phases of the subject have been studied independently by many investigators. Also, it is now a subject of investigation at various laboratories in the United States and in foreign countries. Notwithstanding this extensive investigation, ball milling still remains a subject of some speculation. This paper presents the results of an experimental study of some of the factors entering into ball mill grinding.

Jan 1, 1931

By H. K. Shearer

Oil production in north Louisiana in 1937 was 28,668,070 bbl., an increase of 1,896,925 bbl., or 7.1 per cent over 1936, as against an increase of 178 per cent from 1935 to 1936. Gas production of 301,148 million cu. ft. from gas wells and 17,330 million cu. ft. of casinghead gas, a total of 318,483 million, was an increase of 33,483 million cu. ft., or 11.7 per cent over 1936. Well completions numbered 716, with 411 oil wells, 175 gas wells and 130 dry holes; compared with 346, 109 and 78, respectively, in 1936. There were 58 wildcat dry holes. In addition to the wildcat producers described and tabulated with the fields, there were two small, shallow gas wells in Sabine and Tensas Parishes, which did not open fields of any present importance. At the close of 1937 there were only five wildcat tests actually drilling, with nine others shut down or temporarily abandoned. Chief interest during 1937 was in development rather than discoveries. The only real discoveries were two deep gas and distillate fields, Bear Creek and Ruston. There were also three completions of gas-distillate producers from deeper formations in old fields, of which the most important was at Cotton Valley, one discovery of oil in a previously known gas sand and five or six extensions of some importance. Geological Section The columnar section in south Arkansas (Fig. 1, p. 317) also applies in north Louisiana, with a few changes noted below. The oldest known formation in north Louisiana is a bed of rock salt. Except on salt domes, only one well at Rodessa has been drilled into this salt, but it has been penetrated by a number of wells in south Arkansas. Salt domes have been discovered near Vicksburg and Hattiesburg, Miss., and a deep well in Limestone County, Texas, has drilled into rock salt. In Louisiana the distance between the "interior salt-dome basin" and a salt dome of the "Gulf Coast salt basin" is hardly 60 miles. In short, evidence is accumulating to indicate that all of Louisiana, with the possible

Jan 1, 1938

By J. E. Hove

The high temperature physical properties of graphite are reviewed and interpreted in the light of present day knowledge of the mechanisms affecting these properties. The thermal and mechanical behaviors only are discussed and, whenever possible, comparisons are made with other refractory materials. Possible further studies are indicated, including some carbide work. AS long as the term high temperature implied only temperatures up to about 1000°C, the materials problems which arose could usually be handled by fairly conventional metal alloy types, such as the Co-Cr-Ni superalloys, for which there exists a great deal of technology. Perhaps this temperature can still be considered an upper limit for normal applications, but it is certainly true that the number of abnormal applications is increasing rapidly. The advent, in recent years, of ram-jet and rocket missiles and of high power nuclear reactor heat sources has raised a host of questions concerning the basic problem of what material to use in the temperature range up to 2000°C and higher. While there are, of course, many metals, in the second and third transition series, which melt at considerably higher temperatures than this, these metals are, at present, pretty well excluded from practical use by other considerations, such as re-crystallization, chemical activity, or excessive plastic deformation. The behavior of metals, from the standpoint of dislocation theory, is just beginning to be understood and thus there is some hope for the future development of very high temperature metals, but the immediate problems would most logically appear to have solutions involving the nonmetals, such as the refractory ceramics and graphite. For this reason, there is presently a great deal of engineering and experimental research being performed on the latter materials, much of this research being exploratory in the sense of gathering new property data. The situation, so far as graphite is concerned, is somewhat more fortunate than with the other refractory solids in the sense that a great deal is already known about its basic properties. This stems both from the fact that the carbon-carbon bond has been of interest to chemists for a long time (and graphite can be considered as a very large aromatic molecule, if desired) and the fact that its properties, both as a function of temperature and of radiation damage, are of critical importance to nuclear reactor designers. It is still true, of course, that such fundamental questions as why graphite remains solid to such a high temperature and why it has such a high thermal conductivity cannot entirely be answered at the present time. It is, nonetheless, meaningful and instructive to consider such problems in the light of existing knowledge. This is what the present paper will attempt to do. Before going on, it may be appropriate to classify graphite and justify its discussion before readers primarily interested in metals. Graphite is comparatively unique among materials in that there is always a property or group of properties which precludes calling it either a metal, a semiconductor, or a ceramic. It has the high electrical and thermal conductivities of a metal, but the artificial, poly-crystalline types show a negative thermal coefficient of electrical resistivity, generally characteristic of semiconductors. On the other hand, semiconductors, by definition, show an ever increasing resistivity as the temperature is lowered, whereas graphite approaches a finite, and, indeed, a rather low resistivity in the region of 10°K and, furthermore, a good single crystal of graphite has a positive temperature coefficient, as for a metal.' On still another hand, its porosity and brittleness at lower temperatures would put graphite in the ceramic class although, unlike most ceramics, it is readily machinable and has a high resistance to thermal shock. All things considered, it is probably more nearly appropriate to call graphite a metal than anything else. Although certainly outstanding in some ways, graphite has its peculiarities and, especially if the reader is unfamiliar with the data, it is probably valuable to review some representative property variations at high temperature. This review is meant to be mainly illustrative and no attempt has been made to be exhaustive. Review of High Temperature Properties At ordinary pressures, graphite does not melt, but sublimes directly into the gaseous phase at about 3700°C. Although the phase equilibrium diagram is still in some doubt, graphite will melt, at a slightly higher temperature, at pressures in excess of about 100 atm. The chief difficulty of using graphite in an oxidizing atmosphere is that the reaction rate becomes quite high at fairly low temperatures. If a threshold oxidation temperature2 is defined as the temperature at which graphite loses 1 pet of its weight in 24 hr, the value in air is 450°, the value in steam is 700°, and the value in carbon dioxide is 900°C. Efforts are presently being made to raise this threshold temperature either by impregnation with a retardant of some type (sodium tung-state and phosphoric acid, for example) or by a suitable metal or oxide coating. It is probably fair to say that, to date, these attempts have not shown any outstanding success in all respects. Most commercial graphites are fabricated by impregnating a carbon flour (say of coke or lampblack particles) with some type of hydrocarbon

Jan 1, 1959

By H. R. Fife

AN extended study of dustproofing Freeport-seam coal has empha-sized several fundamental features in the successful treating of bituminous coals. The extent of the exposed surface area and its absorption proper-ties for the dust-retaining film were found to be the most critical factors affecting the efficiency of fly-dust prevention. From recently published screen data and specific surface-area measure-ments on United Kingdom coals, an approximation of the surface exposed by mine-run coal and by 1-in. slack was made. The total surface area exposed by an average ton of this mine-run coal was estimated at 3768 sq. yd., while a ton of 1-in. slack represents a total surface area of 8779 sq. yd. with no additions for porosity. It is important in coal treating to consider that in mine-run coal the fraction above 1/4 in. in size represents 79.5 per cent of the total weight, but only 4 per cent of the total surface, while the fraction below 150 mesh contains 47 per cent of the total surface and only 1.2 per cent of the total weight. Also, one should appreciate that, in a 1-in. slack, the domestic stoker fraction (1 in. to 8 mesh) contains 76.3 per cent of the weight and 8.2 per cent of the surface, while the fraction below 150 mesh represents 3.3 per cent by weight and 54.8 per cent by sur-face area. Wax extraction data on 1-in. to 0 slack from mine-run treated Free-port-seam coal showed that the coating was distributed uniformly as a function of exposed surface; hence, nonuniformly on a weight basis. This distribution of the coating on mine-run coal therefore limits the extent of treating that is desirable on bituminous coal at this point in the preparation. The treatment of Freeport mine-run coal before it reached the tipple gave a 70 to 80 per cent reduction of fly-dust in the tipple, a satisfactory treated commercial slack coal, and an indicated change in the trend of tipple degradation. The premium-treated domestic sizes required a supplemental treatment for complete dustproofness.

Jan 1, 1937

By J. E. Jopling, J. R. Chenneour, E. L. Derby, S. R. Elliott

The Marquette range, on which are situated the iron mines of Mar-quette County, together with a few in Baraga County, Mich., extends from a point 10 miles southwest of Marquette westward for 30 miles. The tracts are usually a multiple of the standard 40-acre parcel, which is the smallest government subdivision of a square mile or section. About half of the mines are held in fee, these being owned by the older mining companies. Some of them date back to about 1880, and a few are as early as 1850. During the past 40 years most of the mines opened have been on leased lands, the royalty being either for a stated amount per ton or a percentage of the selling price of the ore at the lower lake ports, or the selling price on board of cars at the mine. The first merchantable body of ore discovered in the Lake Superior district was found, in 1845, at what is known as the Jackson mine, near Negaunee. This ore was hard hematite. After unprofitable attempts had been made, in 1848, to smelt it in forges, shipments were begun to lower lake ports, which increased rapidly upon the completion of the locks at Sault Ste. Marie, in 1855, and the railroad from the mines to Marquette, in 1857. Beginning with the Pioneer, in 1858, a number of small charcoal furnaces were built to smelt a part of the product. At various points in the upper and lower peninsulas, large charcoal furnaces are still making iron from the ores of the Marquette range. In connection with these furnaces are byproduct plants. As the deposits were opened up, soft ore was encountered, but for a few years this was disregaided, as only the hard ore was used. Underground mining was begun about 1880 and during the next few years the open-pit mines producing high-grade ore were exhausted. The first mines in the district were owned by the Jackson, Cleveland, Lake Superior, Lake Angeline, Champion, Iron Cliffs, Humboldt, Republic, and Michigamme companies. Many of these companies have been merged in the holdings of The Cleveland-Cliffs Iron Co., which controls most of the tonnage of the district.

Jan 1, 1925

By W. V. Green

Creep of tantalum was measured at temperatures from 0.6 to 0.89 of the absolute melting temperature. The creep curves include first, second, and third stages. Steady-state creep rate depends on the fourth power of stress. The activation energy for creep throughout this temperature range is approximately 114 kcal per mole, measured by the aT technique. Subgrain formation occurs as a result of creep strain, and pile-up dislocation arrays are observed in etch-pit patterns. BECAUSE of its high melting point-which is exceeded only by those of rhenium and tungsten—and its high room-temperature ductility compared to most of the other high-melting-point metals, tantalum will undoubtedly be utilized in an increasing number of high-temperature applications. Alloying studies directed toward increased high-temperature strength must use data on tantalum itself as a base line in order to evaluate the effectiveness of the alloying additions. However, to date, no systematic study of creep of tantalum at temperatures above one-half of its melting point has been reported in the literature. Conway, Salyards, McCullough, and Flagella1 have measured linear creep rate of tantalum sheet as a function of stress, but at only one temperature, 2600°C. This paper describes a relatively thorough study of the high-temperature creep of tantalum. METHOD Material Tested. The commercially supplied, l/2-innch-diameter tantalum rod used for this work was electron-beam-melted, cold-forged, rolled, swaged, cleaned chemically, and vacuum-annealed for 1 hr at 1000°C, all by its manufacturer. The vendor's analysis included 60 to 170 ppm C, 3.4 to 4.2 ppm H, 60 to 80 ppm 0, 15 ppm N, and a hardness ranging from 66 to 81 Bhn and averaging 76 Bhn. Creep eimens Used. Two creep-tested specimens are shown in Fig. 1. The 1/4 in.-diameter gage section was 3/4 to 1 in. long, and terminated either at shoulders 5 mils high or at 20-mil-diameter tantalum wires spot-welded to the circumference of the gage section. Both kinds of shoulders served equally well as fiducial marks for optical strain measurements. The spot welding did not alter the creep behavior in any detectable way; the 5-mil- high sharp shoulders did not result in any detectable localized effect on the strain. Before testing, each tensile bar was first mechanically polished -id then electrochemically polished according to the method referred to by Forgeng2 as the "Thompson Ramo Woolridge" method, which was suitable for tantalum after small adjustments of technique were made. Two tensile bars tested at low stresses had 1/8-in.-diameter gage sections and utilized only the weight of the bottom grip for the applied load. Although these diameters were smaller than were desired for other reasons, applied loads were known with high precision in the tests in which they were used. Testing Procedure. Two different constant-load creep-testing machines were employed, one of which has been described by Smith, Olson, and Brown.3 In both, the tensile bar is held vertically on the axis of a cylindrical tungsten tube or screen heater by threaded tungsten grips. The tensile bars and associated grips are heated by radiation from the incandescent heaters, which are heated by their own electrical resistance. Both testing machines use pins to hold the bottom grips in place. The load is applied to a tensile bar through hanging weights, a constant force-multiplication lever, a pull rod sealed to the chamber lid, and a top grip threaded to the pull rod at one end and to the tensile bar at the other. In one machine, the vacuum seal is a bellows with a low spring constant; in the other, the seal involves a rotating "0 ring". With the latter, rotation is converted to translation with a crank shaft, so that elongation of the tensile bar is accommodated with no change of tensile load. The incandescent tensile bar is viewed by an external optical system through slots in the radiation shields and heater, and an enlarged image is projected on a ground-glass screen. Gage-length measurements are made on this image with cathetometers on traveling microscopes. With regard to creep-test results, the two machines were identical. Thorium oxide coatings were applied to the threaded ends of the tensile bars, to prevent diffusion welding of the tensile bars to the grips during testing. Specimen temperatures were measured with an L. & N. optical pyrometer which had been calibrated against a standard carbon arc, and were corrected fir window absorption by calculation from the measured spectral transmittance of the quartz observation windows. Longitudinal temperature gradients in the tensile-bar gage length and temperature drifts during testing were detectable but small, and were estimated to be 10°C or less. Accuracy of temperature measurement was confirmed by comparing the temperature measured on the surface of a special

Jan 1, 1965

By W. M. Robertson

The kinetics of grain boundary groove formation on copper surfaces immersed in liquid lead have been studied over the temperature range of 400° to 900°C. The groove widths were Proportional to the cube root of the annealing time, indicating that the diffusion of copper through the saturated liquid-lead solution is the mechanism by which grooves form. The rate constant for the process can be calculated by a theory due to Mullins. Using published data for the solubility of copper in liquid lead, for the interfacial energy of the solid copper-liquid lead interface, and for the diffusion coefficient of copper in liquid lead, the calculated rate constants almost exactly reproduce the measured values over the entire temperature range. The decay of scratches placed on copper surfaces has also been studied. The rate constant for scratch decay agrees with that for grain boundary groove growth, though scratch decay is sensitive to convection currents in the liquid. The interaction of solid and liquid metals has been studied extensively and has been found to be rather complex. Many of the studies have been complicated by a host of competing effects, including temperature gradients, concentration gradients, the formation of one or more intermetallic phases, natural or forced convection, and the presence in both the solid and liquid of considerable amounts of impurities and alloying elements. Recently theories have been developed of changes in surface profiles driven by capillary forces,' which allow the interaction of the solid and liquid to be analyzed quite directly. The present paper reports a study of the formation of grain boundary grooves on pure copper immersed in liquid lead, which allows the theory to be checked quantitatively. The Cu-Pb equilibrium diagram is quite simple: there are no intermetallic compounds, copper is just slightly soluble in liquid lead, and lead is almost completely insoluble in solid copper.2 The Cu-Pb system has been studied extensively,3-9 and all of the quantities—interfacial energy, diffusion coefficients, and equilibrium solubilities-necessary to calculate the rate of groove growth by a volume-diffusion mechanism are known. The kinetics of grain boundary grooving and scratch smoothing have been studied on the noble metals and the iron group metals in a reducing atmosphere or in vacuum.10 The main interest of these studies has been the determination of surface-diffusion coefficients at metal-gas interfaces using the theories developed by Mullins.1 The present paper uses similar methods for the study of diffusion processes at the interface between two condensed phases. There has been one previous study" of the kinetics of groove growth in a solid-liquid system, which, however, was troubled by the fact that neither interface energies nor diffusion coefficients were known in the Ni-S system studied. THEORY The theory of grain boundary groove growth has been developed by Mullins for the cases of volume diffusion," surface diffusion," and a combination of the two processes.14 He has also analyzed the kinetics of the flattening of a scratched surface by these processes.l5,l6 Several assumptions and approximations were used in the derivations of the surface profile shapes. The applicability of these assumptions and approximations to the present system will be considered in the discussion. At the intersection of a grain boundary with an initially flat interface the equilibrium between the interfacial energy and the grain boundary energy establishes an equilibrium groove angle. This induces curvatures in the interface. The chemical potential of material at a curved interface is higher than at a flat interface, so that material moves away from the region of the grain boundary. Mullins' calculations indicated that the groove profile would be similar to that shown schematically in Fig. 1. Small humps form above the level of the original flat surface. For a volume-diffusion mechanism the separation, w, of these humps at a time, t, is given by and where co is the equilibrium concentration of the solid in the liquid, y, the solid-liquid interfacial free energy, O the volume occupied by a solute atom in the liquid, D the diffusion coefficient of the solid in the liquid, and kT has its usual meaning. For a surface-diffusion mechanism the groove width is proportional to the fourth root of the time. For grooves forming by a combined surface and volume-diffusion mechanism the exponent of the

Jan 1, 1965

By A. Styka, G. Fischer, S. Tour

Described herein are the results obtained during research work involving coating titanium alloys with molybdenum by vapor-deposition methods. Results show that the method can be used successfully to deposit hard adherent wear-resistant coating of methodmetallic molybdenum on titanium or titanium alloys without changing the microstructure of the titanium base. PRODUCTION and use of titanium and its alloys have increased tremendously in the past few years. The physical, mechanical, and chemical properties of this engineering metal have caused considerable enthusiasm among metallurgists and engineers. However, as with all materials, there are some drawbacks. For example, titanium is susceptible to seizing and galling on wearing surfaces. In order to produce a good wear-resistant surface, many investigations have been conducted evaluating oxidizing, carburizing, nitriding, carbonitriding, sili-conizing, and chromizing of titanium. All of these processes require high temperatures for rather extensive periods of time. It has been possible to produce hard surfaces on titanium and its alloys by a number of these processes at the expense of a deterioration of the physical properties of the base material. A practical solution to the problem of providing titanium and titanium alloy parts with a satisfactory wear-resistant nongalling surface must be one that does not involve excessive temperatures for long periods of time. Sam Tour & Co. Inc. has completed a research and development contract for the United States Army Ordnance Corps on vapor deposition of molybdenum on titanium and titanium alloys. On the basis of results obtained from the research program, titanium alloys can be coated successfully with molybdenum to provide a hard wear-resistant surface without harm to their base mechanical properties. The remainder of this article is a description of the techniques used to apply the coating and the results obtained from wear tests on molybdenum-coated titanium. Theory Basically, the technique used was the application of molybdenum by a vapor-deposition method, thermal decomposition of molybdenum hexacarbonyl [Mo(CO)] with hydrogen as the carrier gas. The selection of this method was based chiefly on the following considerations: 1—low plating temperature which would minimize excessive grain growth, 2— low decomposition temperature of the carbonyl, 3— possibilities of controlling the hardness of the plate by adjusting the carbon content using the plating temperature and pressure as the primary variables, 4—use of high vacuum, thereby avoiding unnecessary oxidation and other complex reactions with the atmosphere. Free energy data1 show the strong tendency for titanium to combine with O2 N2 or carbon from normal temperatures to temperatures above its melting point. To maintain the titanium in a film free condition, the use of as high a vacuum as possible is indicated. The literature' indicates that the reaction product of hydrogen with titanium is unstable in vacuum at around 400°C. 5—Although it is indicated from the thermodynamic standpoint that there is little possibility of removing carbon from either titanium or molybdenum, the work of Lander and Germer -ndicates that the use of a suitable H,/CO ratio is somewhat effective in minimizing carbon deposition. 6—Availability of molybdenum carbonyl. In the simplest form, the conditions of equilibrium3 in chemical reactions involving decomposition of carbonyl are as follows: Mo (CO) ? Mo + 6CO 2CO * C + CO,. The plating rate is proportional to the rate of evolution of CO from the decomposed carbonyl, i.e., it is proportional to the pressure of the gaseous decomposition products. Carbon released from CO gas is the significant constituent for the variability of the physical properties of the product. High carbon deposition is favored by increasing pressure. Limitations are imposed in the selection of plating temperature and pressure. Excessive temperature re-

Jan 1, 1956

By G. B. Misra

Though resistance to flow offered by mine airways supported with timber sets has been an object of study over the last half century, no accurate relation has yet been established from which prediction of the resistance coefficient of a projected timbered airway can be made. Zenofontowa et al. developed an empirical relation, but this relation has not been found to satisfactorily correlate experimental data obtained by Sales and Hinsley. This led the author to develop a set of simple theoretical relations between the resistance coefficient of timbered airways and the various parameters affecting it, such as the type and spacing of sets as well as the shape and size of members forming the set. Experiments were designed with the help of a laboratory model airway to verify the validity of the relations developed. With the experiments conducted so far with 4, 3 and 1-piece sets of 3.4 x 3.4, 2..5 x 2.5, and 4.5 X 4.5-cm square-section timbers in a 45.8 x 38-cm model airway, the theoretical relations have been shown to hold.

Jan 1, 1972

EDUCATION for the mineral industry was at first a single comprehensive curriculum, but it was early recognized that the main basis of mining is physics, while that of metallurgy is chemistry. The first school to offer curricula leading to degrees in mineral industry education in the United States (1853) had separate ones in mining and metallurgy. The Columbia School of Mines (the fist really successful one) had only a single curriculum when it opened in 1864, but within a few years had so reorganized its work that it offered curricula in mining, metallurgy, geology, chemistry, and civil engineering. Interest in the metallurgy or geology curricula was slight at fist, and for the next 30 years the great majority of Columbia students took the mining curriculum, probably partly because it contained nearly as much geology as the geology curriculum, practically all the metallurgy, and most of the chemistry, and partly because of the degree awarded for it. Other schools kept their mining curricula equally broad, and as late as 1900-1910 men were graduating as mining engineers who were practically as well prepared to make geology or metallurgy their life work as they were for mining. Gradually, however, the subject matter of mining geology and metallurgy became so enriched through research and development that separate curricula in them became worth while; their progressive development is the subject of another chapter. Mining curricula also began to be somewhat diversified, and schools in areas where coal mining was of outstanding importance began to offer options in coal mining, the earlier curricula having been chiefly aimed at metal mining. The petroleum industry began its meteoric rise about the same time as mineral instruction in this country, but little more of applied science attended its birth than had attended such ancient practical arts as copper and iron

Jan 1, 1941

By Robert W. Metcalf

THE name "tripoli" is used to designate a number of more or less similar types of silica of sedimentary origin. Usually they are spoken of as "soft" silicas, and are light, very fine grained, porous, and friable. Structure is microcrystalline or cryptocrystalline. The deposits are the residual product of weathering and occur in massive form, either blocky or in friable masses. Tripoli is the end product of the weathering of siliceous Limestones, cherty limestones, or cherts. Weathering removes the calcium carbon- ate, leaving a finely divided siliceous residue to which the name "tripoli" has been applied. Authorities differ as to whether the chert accumulates first and is converted into tripoli or the tripoli is derived by direct decay from various forms of silica during initial weathering of the Limestone. It has also been asserted that tripolis were formed in situ in essentially their present condition as a flocculent, colloidal silica, but it is now believed by most geologists that varying degrees of pressure, combined with one or more methods of origin, have influenced the characteristics of the deposits. Considerable confusion has existed as to what constitutes tripoli. Owing to the similarity of names, tripolite, a type of diatomaceous earth found originally in Tripoli in northern Africa, has been erroneously called tripoli. Tripoli, however, contains no diatoms, the distinguishing characteristic of diatomaceous earth. The material mined in the Missouri-Oklahoma area has been considered by the trade to be the type material, and many feel that the term "tripoli" should more properly be restricted to the product of this region. Although also designated as soft silica, it would be less misleading, perhaps, if the siliceous material mined in southern Illinois were called amorphous silica. Both the Missouri-Oklahoma and Illinois materials are very high in silica. Different in composition, as it is very much lower in silica content than tripoli or amorphous silica, yet included under the classification of tripoli in Bureau of Mines statistical data, is the small but important output of rottenstone in Lycoming County, Pennsylvania. The principal justification for grouping these three types of silica is similarity of use.

Jan 1, 1949

By W. A. Wood, W. H. Reimann, K. R. Sargant

A study is made of the microstructural changes produced in armco and pure iron subjected to alternating torsion at amplitudes above and below the knee of the S/N curve. The aim was to identify the basic mechanisms of fatigue and to find why they should give rise to a sharp S/N knee in contrast to the type of S/N curve shown by fcc metals. It is found that the basic structural change above the knee in the iron is a pronounced cell formation in the grains, which determines irregular micro-cracks, and below the knee a dispersion of fine slip that determines a dispersed pore formation in the grains. Comparison of these changes with those in fcc metals similarly tested shows that they do not include an intermediate structural change, a concentrating of slip in narrow bands with associated slip-band cracking, that characterizes the fcc metals and accounts for their different type of S/N curve. RECENT conferences on basic mechanisms of fatigue emphasize that fatigue damage takes many forms: for example, cracking in slip bands (Thompson1), at grain boundaries and inclusions (Hempel'), at precipitation zones in alloys (Han-stock, Forsythe), or at surface notch-peak effects, both hypothetical (Mott, cottrel16) and observed (Wood). Evidently it is not easy to see in this diversity a basic mechanism. At the same time the contributions suggest that some reconciliation may be possible if distinctions are drawn between three phases of the fatigue process: initiation of damage at nuclei, distribution of these nuclei, and the final macroscopic crack system. In initiation, the relevant features appear to be that nuclei may appear early, at least by 1/100th to 1/1000th of the life of a test specimen; that they may do so at many independent centers, appearing according to some observationsa as pores or voids; and that they are not necessarily self-propagating, damage spreading rather by their multiplication. In distribution, the relevant feature appears to be that they form preferentially in zones where the microstructure becomes abnormally strained (as defined more closely below). Now in these two phases the basic fatigue process should be systematic. But, at the same time, the "abnormal strains" in particular set the stage for considerable diversity in the final phase of macroscopic cracking, for where zones of abnormal strain develop will depend on what kind of fatigue deformation is applied and what kind of prior processing the test material has had. On this view it seems desirable to know what in

Jan 1, 1964

By Roland Blanchard

ABSTRACT RECENT discovery at Mount Isa of copper mineralization in commercial amount at a depth of 1000 ft., coinciding with downward termination of ore at about the same depth within the larger silver-lead-zinc lenses that have been the standby of Mount Isa's production to date, has been cited as an example in support of mineral zoning. A previous paper by the author and Graham Hall1 furnished a detailed description of the geology of the ore at Mount Isa as exposed up to that time, but necessarily dealt mainly with the silver-lead-zinc mineralization. Most of the geologic facts that constitute the first half of the present paper were set forth in the previous one in much greater detail, with full supporting evidence for the facts cited. The large amount of underground development (approximately 20 miles) and the extensive exploration carried out by diamond drilling (100,000 ft.) at Mount Isa, added to extensive microscope work conducted over a period of years, both by the company's staff and by others, had made possible the calculation within fairly close limits of mineralogical composition of the principal mineralized block of ground down to 1000-ft. depth, and had established closely the mineral succession, with reasons for deposition of the various minerals in the patterns now occupied by them. The geologic facts as outlined in the previous paper remain as stated; but because substantial development within the new copper ore body and further exploratory diamond drilling within the new silver-lead-zinc area (Race-course) have taken place since that paper was written, statements and figures relating to those two areas in the present paper supersede those furnished in the previous one. The recent work likewise has established more clearly the paragenetic relationship between the chalcopyrite and galena. Evidence confirming the relationship is furnished in the present paper. The facts of ore occurrence at Mount Isa show [ACCEPTED ZONAL SUCCESSION Silver sulphantimonides Galena Sphalerite Tetrahedrite Arsenical sulphides Chalcopyrite Pyrrhotite MOUNT ISA SUCCESSION Chalcopyrite In the main but Silver sulphantimonides wholly Tetrahedriteably not Galenacontemporaneous Pyrrhotite Sphalerite Arsenical sulphides They show further: (I) that instead of the silver-lead minerals yielding to increased zinc in depth, the zinc yields to increased silverlead; (2) no dovetailing of the silver-lead-zinc sulphides into chalcopyrite takes place; (3) despite the large amount of pyrrhotite deposited in the district (estimated at upward of 100,000,000 tons), its deposition took place under moderately low temperature conditions; (4) no evidence has been found for increase in temperature of deposition, with depth, to deepest exploration in ore (1495 ft.). The anomalous condition at Mount Isa, both as to the unorthodox mineral succession and the largely unorthodox pattern of mineral distribution, is explained in the present paper,

Jan 1, 1943

By W. S. Reid

In March, 1938, E. P. Fleming, metallurgist for the American Smelting and Refining Co. inaugurated an investigation into the possibilities of recirculating the gases from Dwight-Lloyd sintering machines operating on lead charge, with the twofold object of concentration of the SO2 content and reduction in volume of total gas produced. The possibility of recovering a commercial grade of SO2 gas from D & L machines operating on lead charge had previously been considered by several investigators. Early History of Recirculation The Selby Smelter Commission Report, published by the Bureau of Mines in 1914, contains a chapter by A. E. Wells regarding results obtained at Selby, wherein some of the richer gas was recirculated through a hood over the pallets. Oldright and Miller of the U. S. Bureau of Mines had also made tests at Trail, B.C., and at Kellogg, Idaho. R. C. Rutherford, while at the Chihuahua, Mexico, Smelter of the American Smelting and Refining Co., in May, 1937, proposed recirculation of D & L gases to decrease the volume of gas handled by the baghouse. At none of these plants, however, was the operation commercialized. In July, 1938, Mr. Fleming, in correspondence with the Selby Plant, inquired regarding the possibility of obtaining 6 pct SO2 gas from the Selby D & L machines. At that time, the writer advised that there was slight possibility of obtaining 6 pct SO2 gas without re- circulation, but believed that it was possible with recirculation, and that experimental work toward that end should be tried at some plant where spare D & L machines were available. The foregoing statement was based on the following information then available— 1. Tests on Selby first-over machines showed 2.28 pct SO2 from first windbox and 1.03 pct SO2 from second windbox, and corresponding figures for second-over charge of 0.81 pct SO2 for first windbox and 0.08 pct SO2 for second windbox. 2. Oldright and Miller (US. Bureau of Mines) in 1932 at Bunker Hill, on 42 in. X 22 ft machines found: a. First-over charge—Maximum SO2 concentration (leaving cake) of 9.5 pct. b. First-over charge—SO2 concentration of over 8 pct from the 4 ft to the 12 ft points beyond the front dead-plate and that the concentration then dropped rapidly. c. That approximately 80 pct of the total sulphur eliminated on the second-over machines occurred during the travel of the pallets from the 1 ft to the 6 ft distances from the dead-plate. d. That approximately 94 pct of the total sulphur eliminated on the second-over machines occurred over the first windox. 3. Oldright and Miller (US. Bureau of Mines) in 1932, at Trail, on 42 in. X 50 ft machines found: a. First-over charge—SO2 varied from 2.0 pct to 5.5 pct (leaving cake) from the 12 ft to 28 ft points from the deadplate. b. That the average SO2 increased from 1.0 pct at 7 ft from dead-plate to maximum of 3.3 pct at 20 ft, then dropped to 1.5 pct at 40 ft. c. That on a 22 ft, second-over machine with an 11 in. bed the SO2 varied from 4.5 pct to 6.5 pct from the 2 ft to the 8 ft points from the dead-plate. d. That on the final roast, the SO2 concentration also varied across the pallets; that is, 2 1/2 pct at the side, increasing to 6.0 pct, 5 in. in, and to 7.0 pct at 10 in. to 20 in. in, then decreased vice versa at the opposite side. e. Concluded that most of the sulphur on a 22 ft machine was removed over the first 7 ft of the first windbox; therefore, they partitioned the first windbox so that the exit gas from the second 4 ft section was returned to the surface of the pallets over the fist 7 ft section, and during a seven-day trial the gas from the 4 ft section averaged 2.4 pct SO2, while the recirculated gas from the first 7 ft section only increased to 3.8 pct SO2. (Excess suction over the 7 ft section to prevent escape of SO2 laden gas from the 4 ft section caused dilution by air.)

Jan 1, 1950

The members of the Institute will recall the account given in the March Bulletin of the inauguration exercises of the Engineering Foundation which was inhibited by an initial gift of $200,000 by Mr. Ambrose Swasey, to be administered by the United Engineering Society as trustees. The Engineering Foundation Board is now constituted as follows: GANG DUNN, Chairman, EDWARD D. ADAMS, Vice-Chairman FREDERICK R. HUTTON, Secretary, JOSEPH STRUTHERS, Treasurer, American Society of Civil Engineers. J. WALDO SMITH, CHARLES WARREN HUNT.

Jan 12, 1915