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One of the best known of the early mining districts of Nevada was that at Eureka, where gold was first produced in 1864. While the most productive period for the district was during the early 1900s, production was maintained until World War II. During this time it is said that the Eureka district produced as much as $200 million from over 3,200 km (2,000 miles) of tunnels and workings. The Windfall Mine was discovered in 1902; and a 100 ton cyanide plant was operated there during the periods 1907 to 1912 and 1932 to 1940. Since 1974, however, Windfall Venture has been operating a unique heap leaching facility on the site of the old Windfall Mine. Gold at the Windfall occurs primarily in the Cambrian Hamburg dolomite which has been "sanded" and in which the original cementing material has been destroyed. The gold is micron sized and is accompanied by anomalous amounts of arsenic and mercury; however, the ore is low in base metals which distinguishes it from the typical Eureka district ores. Mining the ore causes it to break down into very fine sizes, approximately 50% minus 150 microns (100 mesh). Conventional heap leaching by spraying proved to be impossible; and extensive test work on alternate methods, aided by the United States Bureau of Mines, was conducted using 9 m (30 ft) high columns and then large tonnage heaps. The leaching procedure adopted was to build 10.6 m (35 ft) high heaps on a 50 mm (2 in.) asphalt pad covered with a layer of gravel for drainage assisted by perforated pipe drains and gravel-packed sumps. A berm is constructed around the top of each pad and cyanide solution is allowed to “pond” on top of the heap. The resulting percolation is at the rate of 24 liters per sq m per hr (0.6 gal per sq ft per hr), a figure about 2.4 times the average used in other heap leaching operations. The dolomite furnishes its own protective alkalinity and no lime or caustic is used in the solution which contains 0.4 kg per mt (0.8 lb per st) of NaCN. Pregnant solution from the heaps averages about 0.7 g Au per mt (0.02 oz per st) with a cyanide content of about 0. 2 kg per mt (0.4 lb per st) and a pH of plus 9. Addition of NaCN brings the pH of the leach solution up to 11 to 12. Carbon adsorption of the gold was originally done in six enclosed columns mounted in a trailer but five conventional columns have been substituted as the size of the operations has increased. Carbon stripping is with hot caustic, cyanide and 10% ethanol solution. The

Jan 1, 1981

By AIME AIME

RECENT experiments in reflected sunlight photography in mine shaft's' and. slopes in the McAlester, Oklahoma, coal-mining district have been so satisfactory as to indicate that such a method has definite scientific value. The entrances to abandoned deep shafts and slopes on Choctaw and Chickasaw Indian coal lands in Oklahoma are being filled or bulk-headed by the U. S. Geological Survey under Public Works Project F. P. 63-C&C. Inasmuch as these mines may be reopened at some future time when there is a demand for coal, H. I. Smith, Chief of the Mining Division, suggested that photographs of deep shafts would be of value. Such photographs would show timber details and the general condition of the walls. Photographic records of the exact status of shafts when filled will facilitate operations in reopening.

Jan 1, 1936

By R. W. Gurry

THERMODYNAMIC calculations indicate that boron is a better deoxidizer than silicon but probably is not quite as effective as aluminum. Boron should, therefore, be readily oxidized out of the open-hearth bath, which implies that it is not recovered in significant concentration from any scrap charged; also that, if added in the ladle, it tends to oxidize out during teeming unless protected by the presence of a. better deoxidizing agent. These conclusions do not apply to liquid cast iron, in which the oxygen content is much lower than in liquid steel. The possibility of conserving certain strategic alloying elements widely used in steelmaking, notably manganeie, chromium and molybdenum, by the use of boron, which in small concentration appears to be extraordinarily effective in promoting hardenability, raises a question as to what extent any boron present in the scrap charged into the open hearth is oxidized out during melting and subsequent refining. This question is significant because the optimum concentration of boron in the finished steel, which is fairly critical, would be very difficult to attain if the boron in the charge were largely retained in the metal. Moreover, unless boron is substantially eliminated in the open-hearth process its use on a large scale would eventually make it impossible to produce boron-free steel except by restricting the charge to virgin material. There is at present, unfortunately, virtually no satisfactory direct evidence to provide an answer to this question; but there are indications from practice that boron is oxidized out in the open hearth in the production of medium or low-carbon steel, although it may be retained if the carbon content remains fairly high; that is, if the oxygen is kept fairly low. In the absence of direct data, it is necessary to rely upon the indications of indirect evidence, the best approach now available being a thermodynamic calculation of the deoxidizing power of boron in liquid steel by the general method used so successfully by Chipman1 in his study of the reactions in the open-hearth process. The thermal data for boron, upon which such a calculation must be based, are reasonably satisfactory; the only quantities not directly determined are the entropy of melting of boron, the activity coefficient of boron in liquid steel, and the activity coefficient of B203 in an open-hearth slag; but these values may be estimated with ample accuracy. The results of this calculation, which is presented later, are given in Table I, together with corresponding data for other deoxidizing elements. This table shows the calculated residual content of oxygen in equilibrium with different residual concentrations of the deoxidizer in the metal;

Jan 1, 1943

By AIME AIME

PERHAPS the most interesting paper of the subsidence session on Monday morning was that by Roland D. Parks entitled "Yieldable Metal Props for Underground Support." This paper described the development of a telescoping prop made from two pieces of pipe. The lower and larger in diameter has cast in it a soft metallic alloy which is slowly extruded through an orifice in the upper and smaller piece of pipe. In this way, the length of the prop decreases gradually as the load from the roof increases. The stress-strain diagram for these props, as tested in the laboratory, is almost ideal, and can be duplicated satisfactorily in successive tests. They have not yet been tested underground. Another paper of much interest was presented by Prof. P. B. Bucky. It is an addition to his series on structural models as applied to mining and was entitled "Effect of Approximately Vertical Cracks in the Behavior of Hori¬zontally Lying Roof Strata." It was illustrated by motion pictures of a model under test. After explaining the un¬derlying theory, the apparatus and the mode of testing, Prof. Bucky set forth the effect of vertical cracks in a mine roof, as follows: (a) the wider the crack, the weaker the roof; (b) where the sides of the crack are in juxtaposition, there is little weakening of the roof; (c) grouting cracks whose sides are not in contact restores the strength of the roof until it may be as strong as, or stronger than the uncracked roof. Small paper props helped sustain the roof. Both the nature of the material and its bonding affect its behavior under stress.

Jan 1, 1933

By R. W. Gurry

Thermodynamic calculations indicate that boron is a better deoxidizer than silicon but probably is not quite as effective as aluminum. Boron should, therefore, be readily oxidized out of the open-hearth bath, which implies that it is not recovered in significant concentration from any scrap charged; also that, if added in the ladle, it tends to oxidize out during teeming unless protected by the presence of a better deoxidizing agent. These conclusions do not apply to liquid cast iron, in which the oxygen content is much lower than in liquid steel. The possibility of conserving certain strategic alloying elements widely used in steelmaking, notably manganese, chromium and molybdenum, by the use of boron, which in small concentration appears to be extraordinarily effective in promoting hardenability, raises a question as to what extent any boron present in the scrap charged into the open hearth is oxidized out during melting and subsequent refining. This question is significant because the optimum concentration of boron in the finished steel, which is fairly critical, would be very difficult to attain if the boron in the charge were largely retained in the metal. Moreover, unless boron is substantially eliminated in the open-hearth process its use on a large scale would eventually make it impossible to produce boron-free steel except by restricting the charge to virgin material. There is at present, unfortunately, virtually no satisfactory direct evidence to provide an answer to this question; but there are indications from practice that boron is oxidized out in the open hearth in the production of medium or low-carbon steel, although it may be retained if the carbon content remains fairly high; that is, if the oxygen is kept fairly low. In the absence of direct data, it is necessary to rely upon the indications of indirect evidence, the best approach now available being a thermodynamic calculation of the deoxidizing power of boron in liquid steel by the general method used so successfully by Chipman1 in his study of the reactions in the open-hearth process. The thermal data for boron, upon which such a calculation must be based, are reasonably satisfactory; the only quantities not directly determined are the entropy of melting of boron, the activity coefficient of boron in liquid steel, and the activity coefficient of B2O3in an open-hearth slag; but these values may be estimated with ample accuracy. The results of this calculation, which is presented later, are given in Table I, together with corresponding data for other deoxidizing elements. This table shows the calculated residual content of oxygen in equilibrium with different residual concentrations of the deoxidizer in the metal;

Jan 1, 1944

By C. E. Stafford

and tougher, and will carry double the tonnage of any of Dr. Dud ley's soft mils. C. E. Stafford, Steelton, Pa.: I must confess my high ap preciation of Dr. Dadlq's conscientious and painstaking work, and of his scientific methds in obtaining the data; but with his method of handling these results and with his conclusions drawn therefrom 1 canuot agree. The reasons for this difference of opinion I will endeavor to explain. It is apparent on inspecting his Plates 6 and 7 that the majority of the slower-wearing rails are from the north track, and generally have a longer time of service, a greater average tonnage per rail, and a smaller avernge tonnage per year per rail than the faster wearing, the majority of which are from the south track, and gener ally have a shorter time of service, a smaller average tonnage per rail, and a greater average tonnage per year per rail. Have these facts any significance Have these different of conditions to which they are subjected any baring on the relative wearing capacity of these rails I venture to say they have. I think, after a study of Table I (page 676), (an arrangement of linee 17 and 18 of Plate a), in connection with Plates 6 and 7, we will find that the slower wear of the 32 best rails is only partly due to qualities inherent in the rails themselves, but is principally due to external conditions favorable to slower wear. In regard to the north and south track, we know that over the rsoiith track come the loaded cam from the West, and that over the north track these cars return, most of them, empty. It is evident that this means for the north track a less average tonirage per rail per year; or, in other words, a lower wheel tonnage. When the load per wheel is less, the resistance and consequently the wear must, necessarily, be less, other things being equal. Time of service, alee, has an important bearing on the question in hand. It has been only within the last five or six years, as Dr. Dudley has pointed out, that the roadbed of the Pennsylvania Rail road has reached its present admirable condition. Before this time the njadbrd was more elastic, more yielding (and probably not uni tbrmly so) than at present. These circumstalices might cause a sofier rail to be more durable than a harder one, owing to the fact that it ulonId yield rnore or less to the bending force of the passing load and would thus get a bearing on each cross-tie. The harder rail, on the other hatid, being stiffer and more. unyielding, would not

Jan 1, 1881

By R. W. Gurry

Thermodynamic calculations indicate that boron is a better deoxidizer than silicon but probably is not quite as effective as aluminum. Boron should, therefore, be readily oxidized out of the open-hearth bath, which implies that it is not recovered in significant concentration from any scrap charged; also that, if added in the ladle, it tends to oxidize out during teeming unless protected by the presence of a better deoxidizing agent. These conclusions do not apply to liquid cast iron, in which the oxygen content is much lower than in liquid steel. The possibility of conserving certain strategic alloying elements widely used in steelmaking, notably manganese, chromium and molybdenum, by the use of boron, which in small concentration appears to be extraordinarily effective in promoting hardenability, raises a question as to what extent any boron present in the scrap charged into the open hearth is oxidized out during melting and subsequent refining. This question is significant because the optimum concentration of boron in the finished steel, which is fairly critical, would be very difficult to attain if the boron in the charge were largely retained in the metal. Moreover, unless boron is substantially eliminated in the open-hearth process its use on a large scale would eventually make it impossible to produce boron-free steel except by restricting the charge to virgin material. There is at present, unfortunately, virtually no satisfactory direct evidence to provide an answer to this question; but there are indications from practice that boron is oxidized out in the open hearth in the production of medium or low-carbon steel, although it may be retained if the carbon content remains fairly high; that is, if the oxygen is kept fairly low. In the absence of direct data, it is necessary to rely upon the indications of indirect evidence, the best approach now available being a thermodynamic calculation of the deoxidizing power of boron in liquid steel by the general method used so successfully by Chipman1 in his study of the reactions in the open-hearth process. The thermal data for boron, upon which such a calculation must be based, are reasonably satisfactory; the only quantities not directly determined are the entropy of melting of boron, the activity coefficient of boron in liquid steel, and the activity coefficient of B2O3in an open-hearth slag; but these values may be estimated with ample accuracy. The results of this calculation, which is presented later, are given in Table I, together with corresponding data for other deoxidizing elements. This table shows the calculated residual content of oxygen in equilibrium with different residual concentrations of the deoxidizer in the metal;

Jan 1, 1944

AS I told you in the chapter on salts, saltpeter is a mixture composed of many substances extracted with fire- and water from arid and manurial soils, from that growth which exudes from new walls or from that loosened soil that is found in tombs or uninhabited caves where the rain cannot enter. It is my belief that it is engendered in these soils from an airy moisture that is drunk in and absorbed by the earthy dryness. Considering its effects, I do not know how to decide and say exactly what the nature of saltpeter is. The learned and very wise physicians find it salty and with a subtle sharpness both in taste and in their medical experiments. Considering its strong biting qualities, they decide to say that it is of a hot and dry nature; on the other hand when they see that it is engendered from the air and that when touched by fire it becomes inflammable and vaporous, and rises with a fearful impetus when mixed in powder for military guns, it manifestly shows itself to be of a hot and moist airy nature. And then when they see that it is shining and transparent with whiteness and is fusible in every fire in a manner corresponding to a thing of a watery nature, and since it. is heavy, it seems that it can be said to be watery in nature. To this is added the experience of touch and of the great cooling action which it has on water in summertime when wine is to be cooled, and since it crushes and breaks with but little pressure, it might be thought to be earthy in nature; especially when it is seen to change into a hard, white stone when burned with an equal amount of sulphur. Thus it seems that every one of the elemental qualities is predominant in it. Now the ancients called this, or a similar thing, nitrum. [150] Pliny, in Book XXXI of his Natural History, has said that it was a thing not much different from salt, that doctors do not seem to have yet known its nature, that it is found in various places, and that the best is found in Macedonia. But among the moderns and especially in our regions, it is not known today what it is that Pliny and other writers refer -to, since according to the aforesaid Pliny and other ancient writers it is a natural mineral. Some say that in place of, the natural kind the artificial will serve for the same medicinal purposes, since it has the same nature and is perhaps more powerful.

Jan 1, 1942

By P. G. Chamberlain, E. R. Podnieks, R. E. Thill

Although published data on the physical properties of rock are voluminous, information is often lacking on the environmental conditions under which such data were acquired. Efforts are frequently directed to improve specimen tolerances and preparation procedures; but investigators often overlook giving the rock environment equally careful control during the testing program. Generally, tests are conducted at existing laboratory room conditions, and the prepared rock specimens are frequently, if not most commonly, air-dried for various lengths of time before testing. The standard testing atmosphere recommended by the American Society for Testing & Materials (ASTM)1 is 73.4°F and 50% relative humidity. To maintain a rock at 50% relative humidity for testing purposes, however, requires special equipment and preconditioning procedures, as this study demonstrates. Relatively small variations in the moisture content of a specimen, for example, due to the coolants or lubricants used during specimen preparation, can cause significant variations in the physical properties measured. Such moisture variations may occur in the rock specimen even after it is air-dried, since laboratory humidity conditions commonly fluctuate from day to day. For these reasons, this study emphasizes procedures for preconditioning and maintaining a controlled environment during testing. Although the effects of moisture or temperature on rock properties have previously been studied, their combined effect on rock properties is unknown. In this study, uniaxial compressive strength, Young's and stiffness moduli, and longitudinal wave velocity were determined and compared under controlled conditions of temperature, moisture, and pressure for 11 environments considered to be of particular interest in laboratory, in-situ, and even simulated lunar environments. The following environments were selected for this program: -250°F under dry, 50%

Jan 1, 1972

By Joseph S. Malesky

The discovery and development of explosives mark one of the most important findings in the history of civilization. Without explosives our vast economic enterprise concerning the mining of coal, copper, iron, aluminum, and various other ores could not function. Explosives are used in all kinds of construction works, in the razing of old buildings, blasting of trenches, driving of tunnels, and in many other instances common to our everyday life. For these reasons explosives are rightfully referred to as the forerunner of progress. An explosive may be defined as a substance (usually a mixture) that, when flame or shock is applied, yields readily to rapid combustion or oxidation, accompanied by the formation of such relatively large quantities of gases as to produce much violence and pressure which, in turn, react against their surroundings and cause what is termed an explosion. By their very nature the action of explosives is destructive and disruptive of adjacent materials. Decomposition of explosives can occur through deflagration, which is rapid burning or combustion, as in the case of black powder, or through detonation, which is an almost instantaneous disruption, as in the case of dynamites and blasting agents. HISTORY OF BLASTING WITH EXPLOSIVES At one time workmen obtained stone blocks for building by grooving the rock with crude picks, driving wooden wedges into niches in the rock, and pouring water on the wedges; the swelling of the wood forced out the blocks. As late as the 17th century, fires were placed against the face of rock to crack it, and water was sometimes dashed on the heated rock to shatter it by sudden cooling. The progress of our country is synonymous with advancement of the improved manufacture and extended use of explosives. Coal had been

Jan 1, 1981

By Leslie F. Tedsen, John E. Dorn, Alan E. Flanigan

It is necessary occasionally to use aluminum-alloy sheet where moderately elevated temperatures are encountered. Considerable attention has been directed toward determining the influence of "artificial aging" on the room-temperature properties of the precipitation-hardenable alloys, as testified by numerous company reports and by references I to 4. Investigations on the properties at elevated temperatures are few, however, and have not always covered the range of times and temperatures of greatest interest. The present investigation was instituted to overcome this deficiency. The work was done for the Office of Production Research and Development of the War Production Board, under the supervision of the War Metallurgy Committee, as a part of the "restricted" Project NRC-548. It has been released for publication by the Office of Production Research and Development. AS is well known, the high-strength aluminum alloys achieve their remarkable properties as a result of precipitation-hardening. In production they are subjected to a solution heat-treatment followed by quenching, to retain the supersaturated solid solution. The solution treatment is followed by "aging" (precipitation-hard- ening) either at room temperature or at a suitable elevated temperature. A considerable increase in tensile and compressive yield stresses results from precipitation at room temperature ("natural aging"). Through the elevated-temperature process ("artificial aging") it is possible to obtain values of yield stress considerably higher than those attainable by natural aging. The increase in yield stress is accompanied by a smaller gain in ultimate tensile stress and by a decrease in elongation. During the first stages of artificial aging the yield stress increases steadily until it reaches a maximum value. In this condition the material is said to be "fully aged." Further exposure results in "averaging," attended by a steady decrease in yield stress. In the production of the artificially aged materials, temperatures and times are selected to achieve full aging. The following important characteristics are associated with the process: 1. The higher the temperature, the more rapidly is the fully aged condition attained. :7

Jan 1, 1946

By S. L. Hoyt

Some of the more important properties of finished materials are strength, ductility, toughness, resistance to alternating and repeated stresses, etc. Of these, the property that appears to have received the least consideration, at least in this country, is toughness, which is due, possibly, to our regarding toughness as a qualitative property or, at any rate, as one that parallels ductility. This arises out of our greater experience with the simple carbon steels in the rolled or forged (non-heat-treated) condition which, qualitatively, are tough if ductile and are not tough if brittle. In this way we have erroneously become accustomed to judging the toughness of a material from its behavior in the tensile or similar test. The point of view presented in the present paper is that toughness, like hardness or tensile strength, should be regarded as an independent property and of sufficient importance to require, in so far as that may be possible, quantitative determinations. If such be true, it becomes at once necessary to devise experimental means for measuring or valuating toughness, and the notched-bar impact test (the Charpy test) is advanced as the most logical test that has so far been developed for this purpose. It is further advanced, with particular emphasis, that we have two kinds of toughness to deal with and, accordingly, they will be dealt with independently. Classification of Materials According to Toughness Toughness has been defined somewhat as follows: Tough materials are those that offer considerable resistance to permanent deformation but which, once such resistance has been overcome, may be deformed plastically, but only by the expenditure of considerable energy. In other words, tough materials may be deformed plastically but they absorb a considerable amount of work in the process. This kind of toughness may be called "static" toughness when the rate of loading is reasonably slow or "dynamic" toughness when the rate of loading is comparatively rapid, as in impact testing, but in all cases the stress distribution is essentially uniform. However, static toughness does not

Jan 1, 1920

By Chester T. Sims, Robert I. Jaffee

The thermoelectric behavior of the Pt—Pt-Re thermocouple and the resistance of rhenium to attack by certain molten metals is discussed. In addition, data are presented on the stress-rupture behavior of drawn wire, the tensile characteristics of rolled sheet, the variation of Young's modulus with temperature, and the effect of specimen size and fabrication method on the work harden ability. Mechanical properties of thoriated rhenium are discussed. This includes data on the effect of thoria in rhenium on tensile properties, ductility, work hardening, and recrystallization. RECENT work by the authors', has described methods of fabrication and some of the physical and mechanical properties of rhenium. Rhenium was established as a high melting, dense, refractory-type metal with favorable mechanical properties. In addition, Todd and co-workers' and others" have studied such properties of rhenium as the work function, specific heat, and the resistance of rhenium to the water cycle. Revelation of these and other properties has led to serious consideration for application as electrical contacts, high temperature thermocouples, and wear resistant materials. chanical properties reported previously,' several additional examinations have been conducted. The stress-rupture behavior and the Young's modulus of rhenium have been investigated at elevated temperatures. Tensile data have been obtained for rolled sheet, and a study of the relative work hardening characteristics of rod, wire, and sheet has been conducted. Variation of Modulus of Elasticity With Temperature—The Young's modulus of a % in. diam annealed rhenium rod was determined from room temperature to 880"C (1620OF). The rod, approximately 6 in. in length, was activated in a transverse vibration apparatus suspended in a furnace. The resonance frequencies of the rod were measured and used to calculate the moduli values. The driven frequency was 569 cycles per sec, and a protective helium atmosphere was used. The data, plotted in Fig. 1, show that the modulus decreases in an approximately linear manner with temperature over the range tested.

Jan 1, 1957

By Albert Sauveur

AT the New York meeting of the Institute, February, 1914, Professor Hopkinson and Sir Robert Hadfield presented an important paper entitled Research with Regard to the Non-Magnetic and Magnetic Conditions of Manganese Steel.1 Any contribution on manganese steel by its discoverer necessarily carries with it much weight and is entitled to serious and close consideration. The momentous discovery of that alloy by Sir Robert Hadfield some 30 years ago was the signal for great activity in the field of alloy steels; and the remarkable results obtained in the last two decades probably constitute the most important modern advance in the metallurgy of steel. The authors of the paper referred to above are unable to reconcile with the allotropic theory the interesting results obtained by them in heat treating manganese steel. When they speak of the allotropic theory, however, I understand that they have more especially in mind the existence of beta iron. It is not my understanding that they question the occurrence of iron in the two allotropic varieties known as gamma and alpha. If I am wrong, I trust they will correct me. A careful consideration of the experimental results reported and discussed by the authors leads me to believe that on the contrary they can be very satisfactorily explained in terms of allotropy and that, in the light of our present knowledge, they cannot be accounted for in any other way. The physical properties of non-magnetic manganese steel described by the authors are those pertaining to iron-carbon alloys in which iron is present in the gamma condition, or, in other words, to austenite. The metal is then characterized by great tenacity and ductility and low elastic limit, while its hardness, mineralogically speaking, is not excessive, but of a special kind termed "tough hardness" by the authors. Even when subjected to the restraining influence of a large amount of manganese and of considerable carbon, however, relatively rapid cooling

Jan 9, 1914

By Leslie F. Tedsen, Alan E. Flanigan, John E. Dorn

It is necessary occasionally to use aluminum-alloy sheet where moderately elevated temperatures are encountered. Considerable attention has been directed toward determining the influence of "artificial aging" on the room-temperature properties of the precipitation-hardenable alloys, as testified by numerous company reports and by references I to 4. Investigations on the properties at elevated temperatures are few, however, and have not always covered the range of times and temperatures of greatest interest. The present investigation was instituted to overcome this deficiency. The work was done for the Office of Production Research and Development of the War Production Board, under the supervision of the War Metallurgy Committee, as a part of the "restricted" Project NRC-548. It has been released for publication by the Office of Production Research and Development. AS is well known, the high-strength aluminum alloys achieve their remarkable properties as a result of precipitation-hardening. In production they are subjected to a solution heat-treatment followed by quenching, to retain the supersaturated solid solution. The solution treatment is followed by "aging" (precipitation-hard- ening) either at room temperature or at a suitable elevated temperature. A considerable increase in tensile and compressive yield stresses results from precipitation at room temperature ("natural aging"). Through the elevated-temperature process ("artificial aging") it is possible to obtain values of yield stress considerably higher than those attainable by natural aging. The increase in yield stress is accompanied by a smaller gain in ultimate tensile stress and by a decrease in elongation. During the first stages of artificial aging the yield stress increases steadily until it reaches a maximum value. In this condition the material is said to be "fully aged." Further exposure results in "averaging," attended by a steady decrease in yield stress. In the production of the artificially aged materials, temperatures and times are selected to achieve full aging. The following important characteristics are associated with the process: 1. The higher the temperature, the more rapidly is the fully aged condition attained. :7

Jan 1, 1946

By R. N. Zitter

PRESENT work was done in connection with a program for obtaining a low energy gap semiconductor suitable for photodetection. The inter-metallic compound InSb, which is now being in-

Jan 1, 1959

By William N. Poundstone

To forecast the future of coal intelligently, one must first consider the market outlook. Coal can be used for many purposes, but currently about 25% of it goes into metallurgical coke, while 75% serves as fuel. Coal for metallurgical coke should show a modest growth for at least the next decade, primarily because of increased exports, but the important factor in the coal outlook is energy. Today, this country faces a serious shortage of energy, and its requirements are growing at an almost unbelievable rate. Last year the United States consumed 68 quadrillion Btu, or double the energy it consumed in 1950, and, if projections are correct, this figure will grow to 150 quadrillion Btu by 1990. Thus, in one working lifetime, the nation's energy consumption is expected to increase by roughly five times. The future of coal hinges on its degree of participation in meeting this energy need. The Federal Power Commission predicts that coal consumed by electric utilities will increase about 4-576 per yr, reaching 472 million tons by 1980 and 615 million tons by 1990. If this projection proves correct, 1980 consumption will be double that of last year and, even more startling, the utility industry alone will use more coal in 1990 than the entire coal industry produced in 1970. This is a tremendous increase, but in view of the projected energy growth, it is difficult to see how this country's needs can be satisfied with- out a coal contribution of this magnitude. Unless some new source such as solar energy is discovered, it must be assumed that the projected energy will come principally from the present-day sources-oil, gas, nuclear materials and coal.

Jan 1, 1971

By Sherwin F. Kelly

One of the most succinct and illuminating perspectives of the field of geophysical exploration to appear in recent years is an article by E. A. Eckhardt, in the magazine Geophysics for October 1949. Although his review covers the year 1948, many of the data presented are apropos to a review of 1949, and form a pertinent background for a consideration of current progress. He presents charts of the world-wide distribution of gravimeter and seismograph activity in oil exploration, which show that surveys in the United States accounted for practically 68%; of all gravity work and 80%; of all seismic activity. Canada ranked second, with a proportion of roughly 6%, in each case; South America accounted for about the same percentage of seismic work, and double that amount for gravity surveys. Within the United States, Texas and Louisiana were the scenes of the greatest activity, both claiming about 60% of all surveys by each method.

Jan 1, 1950

By Floyd C. Kelly

A. HUltgren, .Söderfors, Sweden (written discussion*).—From the results obtained in his own experiments as well as those of Austin and of Grube Mr. Kelley derives a general law, expressed tentatively in the following words: "whenever two metals are brought into intimate contact at a temperature at which diffusion takes place, a comparatively rapid, or abnormal, grain growth results." It is suggested that,, in order adequately to represent the facts, this definition should he restricted by the following qualifications: a and b are the two metals, b diffusing into a. A. At the temperature in question a should exist as phase a 1 having a limited solubility for b. B. The supply of b by diffusion should be sufficient, in view of the rate of diffusion into a 1, to increase the concentration of b above the saturation value in a 1 so as to cause a new phase a2 to form. (7. The phase a2 should have a range of solubility for 6, thus rendering continued diffusion possible. D. In order that the columnar grains may be preserved in the structure the phase a2 should, of course, not suffer transformation on cooling. The phenomenon thus defined may be described as progressive transformation by diffusion. Its mechanism would appear to he as follows: Fig. 17 shows a portion of the equilibrium diagram a-b, Fig. 18 the distribution of b in solution after various periods of diffusion, Fig. 19 represents the structure in cross-section of a cylindrical rod of a at the end of heating period 3. 1. The first effect of diffusion of b into a will be to establish a concentration gradient in phase a1 (1, Fig. 18). When the saturation value for the temperature of the experiment (m, Fig. 17) is reached at the surface, nuclei of, a2 of composition n will form here, and later develop into a continuous layer. Assuming that diffusion proceeds without irregularities and that transformation at any point sets in without lag—i. e., in the moment saturation is exceeded—the transformation a1-a2 will advance inwards on a cylindrical surface concentric with the surface of the rod. The discontinuity of composition at the transformation surface in the position it happens to have at the end of the treatment (3, Fig. 18) will be preserved at room temperature, if the cooling is not particularly slow, and be recorded in the structure as a marked, smooth line, in agreement with Grube's and the author's observations. The shape of the distribution curves in Fig. 18 is also corroborated by the analyses given by Grube. 2. During diffusion, since the secondary phase a2 is always in immediate contact with the saturated part of the primary phase a1, there should be very little lag in the transformation. This means that the first a2 grains formed should grow in preference to the formation of independent nuclei; in other words, columnar growth results. It does not seem necessary to assume, with Green,' whose conception of the phenomenon

Jan 1, 1929

By R. I. Jaffee, J. W. Roberts, D. N. Williams

DISPERSION hardening as an alloying process has aroused increasing interest in the past few years. This alloying procedure, in which an insoluble phase is dispersed randomly through a metal or alloy, is believed to be especially suited for the attainment of creep strength at elevated temperatures since the dispersed phase is metallurgically stable. Another advantage is that the physical properties of the matrix phase, such as electrical conductivity, remain relatively unaffected by alloying. These two characteristics resulted in interest in the applicability of dispersion hardening to copper and copper alloys. A study of copper alloys prepared by powder metallurgy methods has shown some strengthening from oxide dispersions.' However, powder metallurgy processing would not be economical for large scale production of dispersion hardened copper-base alloys. Therefore, the research described in this article was initiated to examine methods of forming dispersion alloys which would not require powder metallurgy processing. If powder metallurgy processing is to be avoided, a method must be found by which the dispersion material can be introduced into and dispersed through the melt before casting. When the dispersed phase is an oxide or similar nonmetallic, it is extremely difficult to form a satisfactory liquid: solid dispersion since successful mixing requires that the melt wet the dispersed phase. It is almost impossible to force a nonwetted particle beneath the melt surface. This difficulty can be avoided, however, if the oxide particles are produced in molten copper by reaction within the melt. The problem would then reduce to maintaining randomness until solidification. Four procedures were considered for producing an oxide particle within molten copper by reaction. In all cases, the intent was to react oxygen (0) with a reactive metal (X) to form an oxide (XO) within the copper melt. These reactions were as follows: 1) (Cu-X), + (O)g (Cu)1 + (XO)S [1] 2) (Cu-X)1 + (Cu2O)s (Cu)x + (XO)S [2] 3) (Cu-OK)1 + (Cu-X)1 (Cu)1+(XO)9 [3] 4) (Cu-OK)1 +(X)s (Cu)1 +(XO)s [4] The reactions were carried out in an 8-lb melt of 99.98 pct Cu maintained in the vicinity of 2200oF by induction heating. Where possible the amount of the reactants was controlled to give 1 to 5 vol pct oxide. Mechanical stirring during the reaction period was used to minimize agglomeration of the reaction product. The presence of a reaction product was determined metallographically by study of an ingot cast from the melt at the end of the reaction period. Reaction [I] was studied by dissolving aluminum in the melt followed by forcing oxygen through the melt. The melts became quite sluggish during the reaction period suggesting that A12O3 was formed. However, the reaction product rose out of the melt rapidly, possibly due to the flushing action of the oxygen stream, and little dispersed phase was formed. Reaction [2] was examined by dissolving aluminum, silicon, or nickel i; the melt and then adding Cu20 (melting point 2250F). This procedure was unsuccessful. Although Cu2O was easily stirred into cop-

Jan 1, 1961