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By E. M. Wise

THOUGH known as the platinum-group metal- the sextuplet, platinum, palladium, iridium. rhodium, osmium, ruthenium, might well be called the American metals or perhaps Pan-American metals, as the ore containing them eras first discovered in South America, and in recent years the largest production has come from North America. The South American alluvial deposits, which also, contain gold, are in active production, as are the alluvial platinum deposits of Alaska, but the main production is from the copper-nickel ores of Sudbury, Ontario. The Russian deposits in the Urals were the source of most of the worlds platinum for about 100 years, but since 1934 have assumed second place. For a time considerable amounts of platinum came from several rather rich deposits in South Africa but these were exhausted quickly. However, a tremendous reserve of lower-grade ore exists there, which could be worked profitably if the price of platinum were considerably higher.

Jan 1, 1942

By KENNETH CROPPER

USUALLY we forget about the things which move along smoothly. There are no causes for worry when there are no troubles. But when troubles arise we must put forth some thought and effort to alleviate them. No one "worries about his automobile until it begins to knock, develop flat tires, or refuses to start. However, when these ailments become apparent we get wide awake on the spot, and do our best to repair the car. So we find ourselves now. The old bus seems to hit all the ditches. There is rough ground on all sides and none of us is able to do anything toward improvement. A state of pessimism stares us in the face, and there is sufficient cause for it. With lead at 3.75 cents, copper about 8 cents, zinc under 4 cents, -and silver about 26 cents, one has a reason for grief. When we think of the 5000 or less men employed in Utah mines and smelters in 1931, as compared with about 12,000 in 1929, the calamity seems even worse. In view of the present economic crisis we cannot even think of new men getting a job.

Jan 1, 1931

By T. E. Leontis, J. P. Murphy

During the last few years, the trend in the aircraft and automotive industries has been toward higher and higher operating engine temperatures. This has created considerable interest in the effect of temperature on the properties of alloys. In the magnesium field, it has been recognized for many years that the addition of cerium imparts high strength and good resistance to creep at elevated temperatures. Beck,' in his treatise on magnesium, has summarized the work of German investigators. This includes the unpublished data of Menking, showing the increase in strength and hardness of extruded alloys containing 2 to 20 per cent Ce at temperatures from 20' to 300°C. (68" to 57z°F.) and the results of Vosskiihler, who demonstrated the improved resistance to creep of alloys containing 6 per cent Ce plus 2 per cent Mn and 0.5 per cent Ce plus 2 per cent Mn at 150°C. (302°F.). Wellinger and Kei12 have also reported the creep properties of a forged magnesium-cerium-man-ganese alloy at 200' and 250°C. (392' and 482°F.). Haughton and Prytherch have determined the tensile properties of various forged magnesium alloys containing cerium, cerium plus manganese, cerium plus calcium, cerium plus nickel, cerium plus nickel plus manganese, and cerium plus cobalt plus manganese at temperatures up to 290°C. (554OF.). Magnesium-cerium alloys have been used in some commercial applications. It is reported that an alloy containing 3 per cent Ce plus 0.5 per cent Mn plus 0.5 per cent Ca is being used on a forged impeller in Great Britain. Two forged parts made from an alloy with a nominal composition of 5 per cent Ce and 2 per cent Mn have been found on the German BMW-8o1D aircraft engine. These two forgings consist of a supercharger impeller and a rear cam-follower guide. In this country, several types of pistons have been made experimentally in both the cast and the forged conditions from an alloy containing 6 per cent Ce plus 2 per cent Mn and in the cast condition from an alloy of magnesium plus 10 per cent Ce. The cast pistons have been tested in various types of internal-combustion engines, with promising results. This paper presents the results of an extensive investigation on the properties of various cerium-containing magnesium alloys in both the cast and the forged conditions. Data are presented to show the beneficial effects of increasing amounts of cerium on the mechanical properties of magnesium at at temperatures' The effects of heat-treatment on the properties of these alloys and the attendant changes in the microstructure are discussed. The alloys investigated most extensively are

Jan 1, 1946

By J. P. Murphy, T. E. Leontis

During the last few years, the trend in the aircraft and automotive industries has been toward higher and higher operating engine temperatures. This has created considerable interest in the effect of temperature on the properties of alloys. In the magnesium field, it has been recognized for many years that the addition of cerium imparts high strength and good resistance to creep at elevated temperatures. Beck,' in his treatise on magnesium, has summarized the work of German investigators. This includes the unpublished data of Menking, showing the increase in strength and hardness of extruded alloys containing 2 to 20 per cent Ce at temperatures from 20' to 300°C. (68" to 57z°F.) and the results of Vosskiihler, who demonstrated the improved resistance to creep of alloys containing 6 per cent Ce plus 2 per cent Mn and 0.5 per cent Ce plus 2 per cent Mn at 150°C. (302°F.). Wellinger and Kei12 have also reported the creep properties of a forged magnesium-cerium-man-ganese alloy at 200' and 250°C. (392' and 482°F.). Haughton and Prytherch have determined the tensile properties of various forged magnesium alloys containing cerium, cerium plus manganese, cerium plus calcium, cerium plus nickel, cerium plus nickel plus manganese, and cerium plus cobalt plus manganese at temperatures up to 290°C. (554OF.). Magnesium-cerium alloys have been used in some commercial applications. It is reported that an alloy containing 3 per cent Ce plus 0.5 per cent Mn plus 0.5 per cent Ca is being used on a forged impeller in Great Britain. Two forged parts made from an alloy with a nominal composition of 5 per cent Ce and 2 per cent Mn have been found on the German BMW-8o1D aircraft engine. These two forgings consist of a supercharger impeller and a rear cam-follower guide. In this country, several types of pistons have been made experimentally in both the cast and the forged conditions from an alloy containing 6 per cent Ce plus 2 per cent Mn and in the cast condition from an alloy of magnesium plus 10 per cent Ce. The cast pistons have been tested in various types of internal-combustion engines, with promising results. This paper presents the results of an extensive investigation on the properties of various cerium-containing magnesium alloys in both the cast and the forged conditions. Data are presented to show the beneficial effects of increasing amounts of cerium on the mechanical properties of magnesium at at temperatures' The effects of heat-treatment on the properties of these alloys and the attendant changes in the microstructure are discussed. The alloys investigated most extensively are

Jan 1, 1946

By Alan M., Bateman

MR. JORALEMON'S dispassionate discussion of this subject in TECHNICAL PUBLICATION 340 of the Institute shows clearly some of the failures and successes of geology in the discovery of ore deposits. He forces us to recognize, with humility, that chance has played a greater part than geology in the recent discovery of several great copper deposits. I think, however, he wrongly ascribes to unexpected or chance discovery some deposits that were found as a direct result of geological investigation. I refer to the Rhodesian copper deposits,, particularly Roan Antelope and Mufulira, both mentioned by him as having been found by chance. Also,. I think Mr. Joralemon's paper, inadvertently, does not- give the proper credit for the early recognition of the possibilities of these deposits. I feel sure that Mr. Joralemon and the gentlemen given credit by him will welcome any further information on this subject that will throw light on what will some day- be of. historical interest and importance. Consequently, I should like to set forth some additional data that throw light on who should receive the most credit, and' to indicate that, in my opinion, sound. geological reasoning and not chance is to be, credited for the development of the. Roan Antelope and Muf ulira mines.

Jan 1, 1931

By R. K. Ham, M. L. Wayman

TD-Nickel has been broken in tension and in fatigue at voom temperature. Rod specimens failed in tension by necking, with axial cracks attributed to voids elongated in the extrusion direction. Fatigue specimens failed in shear. Thin-film electron microscopy showed that the subgrain structure of TD-Nickel was very stable, and that particle-matrix detachment was very difficult, in tension and fatigue. TD-Nickel softened slightly during fatigue but had a high fatigue ratio (0.5at 10' cycles). Fractography suggested that Stage I fatigue crack propagation is greatly extended in TD-Nickel. Td-NICKEL* is a dispersion of 2 pct by volume of thoria (ThO2) in nickel, produced by powder-metallurgical methods including compaction, sintering, and extrusion. The spherical thoria particles, which may have a mean diameter of a few hundred angstroms, are dispersed with a mean planar spacing of a few thousand angstroms. By a combination of cold working and annealing, a subgrain or cell structure of dislocations intimately associated with the dispersion can be produced.' This gives the material useful tensile properties which are extremely resistant to exposure to high temperatures.'-= At the same time, the material shows considerable ductility.3'4 At the beginning of the present work, it was considered of great interest to investigate the mechanical stability of TD-Nickel under conditions of fatigue. On the one hand, materials which derive strength from a cold-worked structure are unstable in that they are susceptible to fatigue softening: in addition, the presence of discontinuities such as the particle-matrix interfaces might be expected to assist in the initiation and propagation of fatigue cracks, in that they may provide local concentrations of internal stress and sites for the initiation of voids." On the other hand, the substantial ductility of TD-Nickel suggests that if it obeys Coffin's relation8 (or the more refined form proposed by Manson9) it should have good fatigue resistance. The initial purpose of this investigation was to assess the importance of these factors. Also, relatively little fundamental work has been done on the mechanism of fatigue in dispersion-strengthened materials. Work on overaged A1-4 pct CU10-12 revealed a very large Bauschinger effect indicative of internal stresses at the particles, and very great fatigue hardening1' presumably due to the multiple slip stimulated by these internal stresses, followed by softening which was initially due to softening in the matrix, but later might have arisen from cracking at the particle-matrix interfaces. The study of overaged Al-4 pct Cu could not settle this latter point by the electron microscopy of thin films, since the dispersion is too coarse. A previous study of the fatigue of internally oxidized copper13 was complicated by inter granular failure, attributed to oxide particles at grain bouhdaries; internal oxidation of single crystals, however, improved their fatigue properties.'3 Investigations of SAP (sintered aluminum powder) are complicated by the complex particle shapes, and the possibility of continuous internal oxide films.14 It was hoped to avoid these difficulties with TD-Nickel, which had the further advantages that it was commercially available and suitable for study by the thin-film technique. 1) MATERIALS AND EXPERIMENTAL PROCEDURE TD-Nickel was purchased from the Driver-Harris Co. as 3/9-in.-diam rod which had been extruded, swaged, and "stress-relieved" (normally at 1010°C for 1 hr). Continuous-radius fatigue specimens with a minimum diameter of -0.1 in. were ground to shape and electropolished in 40 pct phosphoric, 35 pct sul-furic, 25 pct water at 25oC, with a stainless-steel cathode, at -6 v. Fatigue tests were carried out at room temperature with a Sonntag SF-1-U machine operating in push-pull at 1800 cycles per min, and in an Instron TT-C-L modified for reversed stressing at 26 cycles per min as described elsewhere.10 Round tensile specimens were ground with 0.85-in. gage lengths of 0.135 in, diam, electropolished, and tested in a Tinius Olsen hydraulic machine. The surfaces of fatigue specimens were examined with a Reichert metallograph. Discs for electron microscopy with a Siemens Elmiskop I were spark-cut 0.01 in. thick with a modified Servomet 11 employing a tool of moving molybdenum wire, cleaned in 50 pct acetic, 30 pct nitric, 10 pct phosphoric, and 10pctsul-furic at 85oC, and thinned by the window method in the electropolishing solution at -20°C and -6 v. Two-stage replicas (parlodion, then Pt-50 pct C self-shadowed at 40 deg) were taken from fatigue fracture surfaces for electron microscopy. Plane sections parallel to the specimen axis and containing the direction of fatigue crack propagation were polished, etched with Carapella's reagent, and examined optically. Transmission Laue X-ray photographs of as-received material electropolished to a point were used to determine preferred orientation. 2) RESULTS 2.1) The Structure of As-Received Material. Grains -1 µ diam and elongated 20 to 30 u in the direction of the rod axis were observed, With' elongated "intergran-ular" voids (-4 p diam and -90 µ long and identified as such using longitudinal and transverse sections and

Jan 1, 1968

By Allen V. Heyl

This old district is a major zinc and lead source and minor copper and barite source. Ores are chiefly in the Galena Dolomite and in limestones and dolomites of the Decorah and Platteville Formations, all of Middle Ordovician age. Locally, deposits have been mined from Lower Ordovician dolomites and Upper Cambrian sandstones. Small deposits of lead, zinc, and iron sulfides have been found in Upper Ordovician Maquoketa Shale and in Lower and Middle Silurian Edgewood, Kankakee, and Hopkinton Formations. No post-Precambrian igneous rocks are known in the region, and the granitic and metasedimentary Precambrian basement rocks unconformably underlie the district at depths of 1500 to 2000 feet. The strata are gently flexed and faulted, probably largely the result of gentle compressive and rotational adjustments in the underlying crystalline basement, especially along lineaments between basement blocks. Folds of three orders ·of magnitude are recognized, and many related reverse, strike-slip, and normal faults of small to moderate displacements are present. Zinc-lead deposits are commonly linear, arcuate, or elliptical in plan. Most ore occurs as vein fillings in fractures and as breccia fillings and lining vugs, but some is in bedded replacements and impregnations of wall rocks. The ore is in shears, small reverse and bedding- plant faults, joints, and solution-slump structures related to intermediate and small folds. The main primary minerals in their general sequence of deposition are quartz, illite, dolomite, pyrite, marcasite, cobaltite(?), sphalerite, galena, chalcopyrite, millerite, barite, and calcite. Wall-rock alterations include solution of the carbonate rocks, silicification, dolomitization, clay alteration, and sanded dolomite. Oxygenisotope, trace-element, lead-isotope, and sphalerite- stratigraphy studies are in progress. Fluid inclusions in sulfide and gangue minerals are filled with concentrated brines at 120° to 40°C. Sulfides are directly replaced by supergene minerals above the water table at 50 to 100 feet in depth. In this relatively cool climate and limestone environment, smithsonite is in pseudomorphs after sphalerite; solution transport and redeposition of supergene minerals are rare. Ore genesis is postulated by rising hot-water solutions-a mixture of heated connate, magmatic, and meteoric waters.

Jan 1, 1968

By Simon D. Strauss

What are future prospects for U.S. mining? In many quarters the assumption is made that this country has passed its zenith as a mineral producer -- that it is in a period of decline and that it is becoming a have-not nation like Japan and much of Western Europe. These industrial rivals of ours must depend almost entirely on others for their mineral supplies. In trying to answer this question one must of course distinguish between resources and productive capacity. In today's volatile and competitive markets, the definition of what are reserves and what are merely identified resources becomes ever more difficult. Many large deposits have been found that are unlikely to be viable in the marketplace under normal conditions but that can be of significance to the nation's military and industrial security in times of emergency. I should like to draw on personal experience from World War I1 for illustration. 4fter Pearl Harbor great concern developed over the availability of a long 1ist of strategic materials for which this country was largely dependent on imports. Included were a number of minerals of which domestic deposits had been identified. Among these were chromite, manganese ore, mercury, mica and tungsten.

Jan 1, 1982

Henry Louis, Newcastle-upon-Tyne, England (communication to the Secretary): I think very highly of the novel and ingenious device of Prof. Richards for analyzing the movement of the various elements of the jig; it is a method that certainly seems to promise valuable results, if we could only make certain that these various indicator-appliances have no effect upon the action of the jig. I would like, however, to suggest that in future experiments the connection between the plunger indicator-rod and the pencil should be made by means of parallel motions, so as better to reproduce the rectilinear motion of the piston. I should expect, if this were done, that the " curve " of the plunger in the Harz jig, at any rate, would be represented either by straight lines or else by quite regular curves, according to the method by which the plunger is set in motion; the apparent combinatioil of straight line and curve seems difficult to explain. With respect to the water-curve, I am afraid I am completely at fault, but no doubt Prof. Richards can explain my difficulty. In Fig. 2, the areas of the screen-side and the plunger-side of the jig are equal. If the piston be a fair fit and the bottom of

Jan 1, 1897

By D. S. Choi, R. Stefanko

There are a number of complex factors that influence the effectiveness of anchorage to maintain tension in rock bolts. However, a plastic analysis of the anchorage site employing certain simplifying assumptions with application of the Mohr-Coulomb criterion appears to explain the observed phenomena. Such an analysis has been made and a correlation sought with field and laboratory tests. Field tests were made in an anthracite mine in eastern Pennsylvania and included pull tests and long-term tests of a variety of anchorage devices in two basic lengths, 30 and 42 in. in two widely differing seams. Performance is reviewed for wedge, expansion shell, and resin anchorage. Laboratory tests duplicated many of the field conditions but in addition compared the performance of shells with normal and reversed serrations. This performance was compared with the predicted results from the plastic analysis. One of the major problems in conducting long-term underground tests is the selection of suitable instrumentation. All installed bolts were fitted with spherical and hardened washers to insure the best possible torque wrench readings. In addition, commercially available load cells were used. Finally, the performance of a specially developed strain-gage-equipped ring cell is viewed. Rock bolting as a method of support continues to increase with applications in many other industries in addition to mining. Nevertheless, with nearly 55,000,000 roof bolts installed in coal mines alone last year, this remains as the single greatest use. While bolts have frequently supported ground where conventional timbering could not, there are relatively few design criteria; and trial-and-error procedures prevail. Furthermore, there has been a lag in development of suitable instrumentation that is simple to install and read out, sensitive, durable, reliable, safe, and economical in evaluating the effectiveness of a bolt over long periods of time. Therefore, the pull test continues to be the most popular method of evaluating the applicability of a certain type of roof bolt under specific installation conditions. At The Pennsylvania State University in the Dept. of Mining, research has been conducted for a number of years to measure bleed off in carefully controlled laboratory experiments as well as in underground investigations."-' Unfortunately, most of the instrumentation developed has been primarily suitable only for research purposes, not possessing all of the aforementioned characteristics desirable for routine underground use. Other groups also have met with restricted success. Therefore, while relatively crude, the torque wrench continues to remain as the most widely used load measuring device. While both field and laboratory tests continue to be con- ducted, analytical analyses are attempted to discover the more important design parameters in order that more efficient anchorage might be devised. Bolts are being used for a greater variety of purposes in mining. Suspending wire sideframe belt conveyors from roof bolts is a common application. The suspension of a monorail transportation system presents yet another. One such system has just been installed in a recently reopened anthracite mine and is presently being evaluated under production conditions. Preliminary studies revealed that a considerable cost reduction was possible by suspending the monorail on bolts anchored in the top. The monorail was to be installed under two widely differing conditions—a competent sandstone above the Buck Mountain seam and a softer shale top above the Skidmore. The type of anchorage device, length of bolt, and long-term performance, consistent with economy and safety, had to be established for the installation once the decision was made to suspend the system on rock bolts. This paper describes some of the testing procedures leading to a final selection. Theoretical Analysis of Expansion Shell Anchorage A detailed look at an expansion shell assembly might shed some light on the factors involved in the design of a suitable shell, Fig. 1. When a bolt is rotated, the tapered plug is forced downward, expanding the leaves laterally to grip the sides of the hole. Two friction surfaces are present: (1) the interface of the plug and leaf and (2) the interface between leaf and rock. The relationships of these friction planes, geometry of expansion shell, and properties of the rock are important in the design of an expansion shell. Therefore, an analysis assuming the rock to behave as a rigid plastic material with its yield governed by the Mohr-Coulomb criterion was made." Furthermore, the effect of friction between the leaf and rock produced by serrations was analyzed.

Jan 1, 1971

By H. Y. Jennings

An extensive field and laboratory experimental program was carried out to compare the waterflood behavior of carefully preserved soft and unconsolidated cores with measurements on the same cores after extraction. Results obtained from using idealized consolidated and unconsolidated porous media in which wettability could be carefully controlled were contrasted with the preserved core data. The controlled tests on idealized porous media investigated the effect of wettability, flood rate, core length, core permeability and consolidation on the displacement of high viscosity oils. It was concluded from these studies that waterfloods are more favorable when carried out with crude oil in preserved soft and unconsolidated cores than with the same cores after they have been extracted and re-saturated. Waterfloods are usually more favorable when carried out with crude oil in extracted .soft and unconsolidated cores than with refined oil of the .same viscosity in the same cores. The less favorable behavior of extracted soft and unconsolidated cores compared to preserved cores is due to alteration of the core by extraction. Preserved cores saturated with native water and oil should be used for laboratory displacement experiments because they more accurately reflect true reservoir behavior INTRODUCTION The demand for low gravity crude oil created by refinery modernization has focused attention on increasing the production of this viscous crude oil. Billions of barrels are in place in fields that are depleted, or nearly depleted, by primary production mechanisms. Since low gravity reservoirs are relatively recent, geologically, the solid matrix material is usually soft and unconsolidated sand. Such formations are also characterized by a high clay content. Evaluation of sophisticated oil recovery processes with the associated high capital investments has increased the demand for special core analysis tests on material from these soft and unconsolidated sand reservoirs. Data in this paper have resulted from an extensive field and laboratory experimental program. The initial objective vras to provide soft and unconsolidated sand cores for laboratory measurements with as little alteration as possible from their reservoir condition. A secondary objective was to compare the waterflood behavior of these carefully preserved cores with measurements on the same cores after they had been extracted and resaturated. When the comparison showed markedly different behavior the final objective was to attempt to explain the difference by making measurements on idealized porous media free of clay in which initial wettability could be carefully controlled. EXPERIMENTS MATERIALS Core Material The preserved cores used in this study were obtained with as little alteration as possible from their reservoir conditions. Special techniques were developed to satisfy this objective. The cores were cut with native crude whenever the crude had the necessary properties to satisfy the minimum drilling fluid requirements. A pure hydrocarbon chromatographic tracer was added to the crude to provide a simple, safe and inexpensive method to distinguish between oil filtrate and formation oil. Details of the tracer technique used in this study and the procedures used to handle and process the soft, unconsolidated cores have been published.' The core samples were then preserved and packaged at the well site with a dip-applied strippable plastic, or by using a rubber sleeve from a rubber-sleeve core barrel. The final step was to insure that the carefully taken and preserved samples were not altered by processing in the laboratory. Some soft and poorly consolidated sands were carefully shaped in the lab and encased in a protective mounting without disturbing their three-dimensional integrity. Many samples were so poorly consolidated that they literally flowed from the package when the seal was broken. A technique was developed to obtain cylindrical plugs from these samples by using liquid nitrogen as the drilling fluid in a conventional core-drill, drill-press assembly. The idealized porous media consisted of sintered rods of Alundum RA 139, outcrop sandstone identified as Al-hambra sandstone and packs of No. 130 Nevada sand. This sand is 95 per cent 140-200 mesh. (Physical properties of these porous media with those representative of preserved cores are in Table 1.) The natural cores and most of the idealized porous media were 1 1/2-in. in diameter and 3-in. long. The samples used to study the effect of core length were 1 1/2-in. in diameter and 12-in. long. Liquids Water and oil produced from the formations being studied were protected from the atmosphere and collected in carefully cleaned glass or plastic-lined containers. The production was free of chemical additives such as emulsion breakers and corrosion inhibitors. The crude oil was

Jan 1, 1967

By H. L. Hopkins, OHIO, L. W. Kemph, CLEVEL AND, E. V. Ivanso

A balanced system of internal stress is set up in any metallic structure by plastic deformation below the annealing temperature. The internaI stress induced by cold rolling or other fabricating processes is generally recognized and its magnitude is known to be, within certain limits, a function of the degree of cold deformation. The plastic deformation that may accompany rapid cooling from elevated temperatures may not materially change the form of the product. The internal stresses so induced are not, therefore, so evident and nonrecognition of their presence has at times led to engineering failures. The heat treatment of aluminum alloys is a relatively new art and little information is available regarding the magnitude of stresses induced during the commercial heat treatment of aluminum alloy products. As the industrial use of aluminum increases, it is inevitable that products of increasingly large volume will be required. It has become necessary in the present commercial utilization of aluminum to heat-treat castings and forgings weighing hundreds of pounds. One of the factors governing the magnitude of internal stresses arising from rapid cooling from elevated temperatures is that of the size of the structure being treated. Some of the other factors are: cooling rate, elastic properties of the alloy, thermal expansivity, thermal conductivity, and the presence or absence of phase changes. Practically all aluminum alloys have a high coefficient of thermal expansion and some are capable of developing relatively high elastic limits. On the other hand, all commercial aluminum alloys have relatively high thermal conductivities, no invariant phase changes, and the quenching temperatures are comparatively low. In the absence of invariant phase changes involving change in the type of crystallographic lattice, the fundamental basis for the development of internal stress

Jan 1, 1934

By W. W. Anderson

A formula for quantitative efficiency is proposed, in which the efficiency value is a function of the improperly distributed material at the, gravity of separation effected by the cleaning equipment. The misplaced material is expressed as a percentage of the total material discharged from the equipment. Numerous examples are given, demonstrating application of the formula to various types of separation, including multiple-product separations.

Jan 1, 1950

By E. W. Dewing

The nature of solid solutions of sodium in non-paphitic carbon at temperatures near 1000°C has been investigated by an electrolytic technique. The activity coefficient is found to vary strongly with the heat-treatment temperature of the carbon, and an analysis of the energy terms involved suggests that this is due to variations in the Fermi level. The diffusion coefficient for sodium is in the range implying that the sodium atoms (or ions) are not bound to specific sites on the carbon, in agreement with lack of evidence for specific compounds in the activity -composition curves. In the light of These results phenomena occurring in aluminum reduction cell linings are dis-cussed. It is concluded that sodium migrates by diffusion through the carbon lallice and not the pores, and that A14C9 is formed within the lining hy The excess of NaF invariably found in used linings is formed by this reaction and by air oxidation: There has recently been much interest in the swelling of carbon which occurs when it is made cathodic in an aluminum electrolysis cell, and there is general agreement that the phenomenon is due to the penetration of sodium atoms, derived from the reaction on the carbon lattice. (NaF and AlF3 are constituents of the fused-salt electrolyte.) The low-temperature lamellar compounds of potassium with graphite are well-known, and one compound between sodium and graphite has been reported.4 There is, however, virtually no information on the basic chemistry of the interaction of sodium with nongraphitic carbon at high temperatures, although Dell3 has made some fundamental studies of rates of penetration. At the time the present work was carried out these were not available. Rapoport and samoilenkol had measured rates of physical expansion in a dilatometer, using the fractional increase in length of a carbon specimen after electrolysis in a cryolite bath for 2 hr as an index of susceptibility to cathodic swelling. Work here with a similar apparatus showed that expansion (of a 1.5-in.-diam cylindrical specimen) ceased in less than 20 hr, and that the final expansion was much more reproducible than the value at some intermediate time. This suggested that an equilibrium was being set up, and that a thermodynamic approach was required. The results obtained are not as accurate as had been hoped, but they are the only ones of their type available and have enabled useful conclusions to be drawn. The experimental work was divided into two parts: an investigation of the activity-concentration diagram for sodium in carbon, and a rough determination of the diffusion rate. For the former, most of the experiments were made with petroleum coke even though this is not a form of carbon used in cell linings. It has the advantages, however, that it is a homogeneous material, that it is low in ash, and that its structure is reasonably well understood. Anthracites and coal cokes gave results of the same type as obtained with petroleum coke, but the reprodu-cibility from specimen to specimen was extremely poor. EXPERIMENTAL 1) The Activity-Composition Diagram for Sodium in Carbon. The petroleum coke was ground, pressed at 40,000 psi into plates 19 by 9 by 2 mm without added binder, and heat-treated. The sodium activities were established by an electrolytic technique. The carbon was made anodic in a cryolite bath with an aluminum cathode, and a controlled potential, E, applied so that the sodium activity at the anode was given by ln Na = 1n asa - EF/RT [21 where as, is the sodium activity generated by Reaction [I]. The relative activity is sufficient for many purposes and is simply given by The value of Na not at present known, but when the thermodynamics of the Na-A1 system have been worked out it can be derived from the equilibrium

Jan 1, 1963

By D. Atkinson, C. Bodsworth, I. M. Davidson

A geometric model of interstitial solid solutions, which has been used previously as a basis for the prediction of carbon activities in Fe-C austenite, is shown to serve also for the calculation of nitrogen activities in Fe-N austenite. The model has been developed to enable predictions to be made of the activities of an interstitial element in the presence of two host atom species. The activities calculated via the model are shown to be in satisfactory agreement with the measured values in the austenite phase for carbon in Fe-C-Co, Fe-C-Cr, Fe-C-Ni, Fe-C-~n, Fe-C-Si, and Fe-C-V alloys and for nitrogen in Fe-N-Ni alloys. The effect of the second substitu-tional solute on the logarithm of the activity of the interstitial element is expressed as the product of a constant mad the atomic concentration of that solute. The constants so derived we related to the thermo-dynamic interaction coefficients which describe the effect on the activity coefficient of carbon of an added solute element. In recent years the thermodynamic activities of carbon and nitrogen in the single-phase austenite field have been determined for iron binary alloys and for several iron-base ternary alloys. In order to extend the use of these measurements, it is desirable to be able to predict with reasonable accuracy the activities of the interstitials at compositions and temperatures other than those which have been measured experimentally. In all the systems studied to date, the interstitial elements do not conform to ideal behavior. Hence, the available data cannot be extrapolated or interpolated using the simple thermodynamic concepts of solutions. Several models have, therefore, been formulated for the purpose of predicting the activity of an interstitial element in the presence of one species of host atom. These models can be divided into the geometric1"5 and energetic6-' types. The former group is based on the assumption that at low concentrations the activity of the interstitial species is determined by a composition-dependent configurational entropy term and an excess free-energy term which is temperature-dependent but independent of composition. The purpose of this paper is to show that the treatment, based on a geometric model, can be extended to enable predictions to be made of interstitial activities in the presence of two substitutional host atom species. THE CONFIGURATIONAL ENTROPY OF MIXING ICaufman5 has shown that the configurational entropy, S,, for a binary solution comprising of a host atom species, A, and an interstitial species, I, can be expressed as: where NI is the atom fraction of the interstitial species, R is the gas constant, and (2 - 1) is the number of interstitial sites excluded from occupancy by the strain field around each added interstitial atom. The number of interstitial sites per host atom, p, is unityg for the fcc austenite solutions considered here. The configurational entropy of mixing for a ternary solution comprising two substitutional atom species, A and B, and one interstitial species, I, can be derived similarly. Let the number of atoms per mole of each of these species in the solution be represented by «a, ng, and nI. From geometric considerations, it is improbable that the addition of a few atom percent of a second host atom species will change the type of sites (i.e., octahedral) in which the interstitial atom can be accommodated in the austenite lattice. At higher concentrations (determined largely by the relative atomic radii of the atomic species present and any tendency to nonrandom occupancy of the host lattice sites) other types of interstitial sites may become energetically favorable. Restricting consideration to compositions below this limit, for 1 = 1 the number of suitable interstitial sites is given by (n + nB). However, if each interstitial atom excludes from occupancy (Z - 1) additional sites, the total number of sites available for occupation is reduced to (n + ng)/Z. The number of vacant interstitial sites is given by: The total number of recognizable permutations of the atoms must include the recognizable, different configurations of the A and B atoms on the host lattice. Assuming that these arrangements are purely random, and are not affected by the presence of the interstitial species, the total number of recognizable permutations in the ternary alloy is given by: The configurational entropy is obtained by expanding, using Stirling's approximation, and collecting like items, as:

Jan 1, 1969

By David J. Mack, Dennis R. O’Boyle

The mechanical properties of three polycrystalline intermediale Phases that have the y bvass structure were measured in compression between 400° and 900°K. At the lower testing temperatures— termed Region I— no plaslic deformalion occurred prior to brittle fracture. A1 higher temperatuves— lermed Region III—the three phases deformted plaslically for all strain rules from 1.5 to 36.0 x 10-4 sec-1. The homologous temperature for the inilialion of plaslic flow increased in the same order as tile atomic size difference between atoms in each plmse (0.50Tmp for y AgZn, 0.62Tmp for y CuZn, and 0.76 Tmp for y CuCd). The increased flow resistance oj. y CuCd above 0.50Tmp is explaitzed in terms of the more random arrangement of copper and cadmiwn atoms on the laltice sites of&apos; the y bvass slrilctlire. Plaslic deformation of the three intevmiediate phases in the smooth plaslic flow region appears to be controlled by oacancy-induced dislocation climb. RESULTS are reported in this paper on the mechanical properties of three binary intermediate phases having the complex cubic y brass structure (D82, 143m) containing fifty-two atoms in the unit cell. The structure of the prototype y brass phase, y CuZn, was first analyzed by Bradley and Thewlis&apos; based on the X-ray work of Westgren and Phragmen.2 The y brass structure can be visualized as an arrangement of twenty-seven body centered cubes (3 by 3 by 3) into a unit cell containing fifty-four atoms. From this cell the center atom and the four corner atoms are removed and the remaining fifty-two atoms are slightly displaced, resulting in the y brass structure. Approximately thirty-five binary intermediate phases that have an electron to atom ratio of 21:13 have been reported to form the y brass structure. The three y brass intermediate phases selected for this study are formed from elements in groups IB and IIB of the first and second long period. Each compound exists over a composition range that includes the stoi-chiometric composition A5BB (Cu5Zn8, Ag5Zn8, Cu5Cd8). y CuZn (a0 = 9.944A) has solubility limits extending from 57 to 67 at. pct Zn at 500°C apd melts peritecti-cally at 834°C; y AgZn (a0 = 9.326A) has a solubility range from 58 to 63 at. pct Za and melts peritectically at 661°C. y CuCd (a, = 9.596A) melts congruently at 563°C and has a maximum range of solubility extending from 58 to 64 at. pct Cd. In order to minimize coring and microporosity during solidification, the composi- tion of the compounds that form peritectically (y CuZn and y AgZn) was chosen so that the temperature difference between the liquidus and the solidus is only a few degrees centigrade. In selecting y brass compounds for this study, phases were avoided that contained a transition element or that had an electron to atom ratio greater than 1.70. Hume-Rothery et a1.3 has observed that, when the electron to atom ratio of y brass intermediate phases exceeds 1.70, atoms begin to drop out of the unit cell to maintain a constant electron to unit cell ratio. EXPERIMENTAL PROCEDURE Each of the three intermediate phases was prepared from elements having a purity >99.999 pct. Only trace quantities of impurities (<0.0001 pct) were detected by spectrographic analysis of the four elements. A master alloy of each compound weighing approximately 130 g was prepared by melting the elements in evacuated sealed quartz tubes heated in an electric furnace. Specimens having the desired diameter for the mechanical property measurements were obtained by remelting the master alloy in a Vycor tube under argon and drawing specimens from the melt into 4-mm-diam quartz tubes. To obtain a smooth surface on specimens drawn from the melt, the inside of the quartz tube was coated with a thin layer of graphite formed by thermally decompositing acetone. All specimens were imbedded in sealing wax and cut to the proper length with a diamond-impregnated cut-off wheel. The individual specimens (4 mm diam by 8 mm long) were then sealed in evacuated Pyrex tubes and homogenized at 500°C for 72 hr. Chemical composition, variations over the length of the rod (10 cm long) were generally less than 0.2 pct and the analyzed composition differed from the desired composition by less than 0.5 pct.4 Metallographic evaluation of the specimens after homogenization showed no evidence of a second phase in any of the compounds. The average grain size of the specimens after homogenization was 1 to 2 mm. All mechanical property measurements were carried out in an argon atmosphere using a compression apparatus described previously.5 Prior to applying the load to the specimen, the test apparatus was evacuated, back-filled with argon, and heated to the test temperature for 20 min to establish thermal equilibrium. EXPERIMENTAL RESULTS Mechanical properties measured as a function of temperature and strain rate for each of the three y brass phases were similar. From room temperature to the ductile-to-brittle transition temperature, only elastic deformation was observed prior to fracture.

Jan 1, 1968

By H. W. Gillett

CLYDE WILLIAMS has reminded me that in the fall of 1929, gave, in MINING AND METALLURGY, an account of the hopes and aspirations of Battelle Memorial Institute, which was then just swinging into initial operation; and that therein I remarked that B.M.I. should stand, as well, for Better Metallurgical Industries, since helping to better them was the Institute&apos;s aim. So he has suggested that some of the betterments of the past fifteen years might well be listed. A yearly summary of progress comes pretty close to the ultimate in futility, for everything proved of value in that year had its inception in earlier years, and everything really new has still to be proved. Plenty of things hailed as wonderful achievements for that year, by some enthusiasts invited to contribute to the summary, turn out in later years to be inglorious flops. But over a decade and a half, betterments that are really such become self-evident, and recounting some of them can be done without guesswork or wishful thinking. An inventory of what was known and utilized in 1929 compared to what is now known and used is not too hard to make. Perhaps the most clear-cut picture of what is known and used at a certain date is drawn by the handbooks, textbooks, and equipment catalogs of that date, with scientific periodical literature forecasting what knowledge may later be used when it is verified and assimilated. The tools available for production or for research limit the application of old and the finding of new knowledge.

Jan 1, 1945

By AIME AIME

ON Tuesday afternoon, Feb. 17, a large and interested audience gathered in the auditorium of the Engineering Societies building to take part in the gold supply symposium that had been arranged for by the Mining Geology Committee. Waldemar Lindgren presided over the gathering and after brief introductory remarks on the international situation as regards lead, silver and gold, called on John Wellington Finch to present an oral abstract of the paper, "Sources and Trends in Gold Production," by R. J. Grant, director of the Mint, and. J. B. Knaebel. This &apos; paper reviewed the gold production of the world, by countries, since 1845, from the statistical viewpoint, leaving to the later speakers discussion of the statistics.

Jan 1, 1931

In the Philippines, where distances are spoken of in terms off fight time, the Sipalay copper mines are two flight hours southeast of Manila on the island of Negros. After landing at the airport in Bacolod, it is then 170 km (106 milers) by surface transportation to Marinduque Mining and Industrial Corp.&apos;s expanding copper operation. While copper deposits were discovered in the area in 1936-and one mine, the Binulig, began operations soon after-it wasn&apos;t until 1956 that stripping at Sipalay and construction of a 4000-t/d (4400-stpd) mill began. The mill went into operation in May 1957, and the first shipment of copper concentrate was made three months later.

Jan 8, 1978

By Richard Kunter

INTRODUCTION Additional work has been done on the CIP circuit at Creede, and a brief description of this work is presented in this paper. DREDGE The original dredge for the Bulldog was built by Al Hack, Inc. of Denver. The dredge cutter head is mounted on a boom made of 6-inch diameter pipe which is raised and lowered by a cable-pulley system. Maximum cutting depth is 8 feet. Slurry from the dredge flows through a floating 6-inch diameter pipe supported on 55-gallon drums which runs from the dredge to the shore and then to a trash screen and pumping system. See Figures 1 and 2. The cutter head, suction pump, winches for dredge movement, and all other operations are controlled from a small operations house located toward the rear of the dredge. All of the basic dredge equipment is mounted on a chassis about 8 ft x 16 ft in size. Additional buoyancy was originally provided by sealed 55-gallon drums supported along the sides of the chassis by a small wooden framework. Additional framework and barrels on the front of the chassis on either side of the cutter boom provided additional stability, particularly when digging in hard material. The dredge was quite stable, but two problems were apparent. For one, it could have been sunk by someone from the shore firing a rifle into all of the barrels. In prime deer-hunting and sportsman country

Jan 1, 1983