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By J. A. Collins

THE process of plastic extension of face-centered cubic single crystal-line rods is so well understood, since the notable studies of Taylor and Elam,1 that the change in orientation of any crystal by slip and rotation may be predicted from the measured elongation. It is customary to assume a very homogeneous deformation, wherein gliding lamellae are free to rotate so that their slip direction continually approaches the axis of the rod, until a second slip system comes into operation; whereupon conjugate slip proceeds quantitatively to an end adjustment with the [112] direction in the axis of the rod. This process has been checked in many face-centered cubic materials and readily permits the preparation of specimens that have been sub-jected to various determinable amounts of shearing action. It is clearly of interest to study in such measurably strained specimens the development of a recrystallized structure on annealing and if possible detect the source of nuclei from which the new crystals grow. Strain-annealing experiments of this character have been performed by others but not in detail sufficient to permit a study, for example, of the number of recrystallized grains vs, the amount of shear. In the experiments now reported, this was done with a wide variety of orientations covering nearly the entire range of slip on a single system and corresponding to amounts of shear (ratio of shearing distance to distance between lamellae) at the conclusion of a test of from 0.08 to 0.57. A particular point was made of determining the crystallite rotation, or small angular range assumed by the octahedral slip plane after these various amounts of shear. The mechanism of recrystallization and the magnitude and effect of recovery on the recrystallization process was investigated.

Jan 1, 1940

Mills Day left a journal of his travel to Ohio and return by way of Pittsburgh in 1810. He left this comment about western Pennsylvania: "June 19. As I proceeded toward Pittsburg, (From Washington and Canonsburg) the country grew more populous. The hills appeared to consist of strata of freestone, iron, coal, and slate. June 20. Its (Pittsburg's) water communication with a vast extent of country and the immense beds of coal in its immediate vicinity render it a place peculiarly adapted to manufactures. Coal may be obtained of a good quality, ready delivered at 5 cents a bushel."1 Until within a year or so of this period, coal was used for domestic purposes, brick-making, by blacksmiths, etc.; now the industry entered a period of rapid growth caused by the introduction of the steam engine. As manufacturing was increasing due to the settlement of the western country, the additional facilities created by mechanical power were welcome. Apparently the first engine was installed in Pittsburgh, in a steam grist mill, in 1808; it is described in the Navigator of 1811: "The water of the boilers are heated by large fires made of stone coal, which is introduced at one end into a grated fire place as long as the cylinders themselves; the quantity of coal consumed daily by these boilers is said to be about twenty bushels, which cost one dollar." Later it mentions the effect of burning coal:

Jan 1, 1942

By R. W. Ph. D. Raymond, Anton Filers, O. H. Hahn

THIS paper will treat of such works only as beneficiate ores directly in the mining districts. And when it is said that more than twenty furnaces exist in Utah, about as many in Nevada, five in Montana, and four in Cerro Gordo, Inyo County, California, it is obvious that a business so extended deserves attention. Wide apart as these different works are located, they have nevertheless to deal in nearly every case with the same or very similar circumstances and conditions, so that, with very few exceptions, virtually the same system of smelting is followed in all these establishments. This is the so-called method of reduction and precipitation in blast-furnaces. As the principal reasons for the employment of a blast-furnace process are to be considered : the low percentage of lead in the ores, the high price of the only available fuel, charcoal, and the exorbitant rates demanded for labor. The reasons why the reduction and precipitation process is preferred to a roasting, reduction, and precipitation process are the high prices of labor and materials, and the preponderance of oxidized ores over sulphurets, though in some cases the latter are quite abundant. The weight of these reasons will be better understood when the character of the ores to be treated and the object of the smelting are more minutely stated. The ores are in nearly all cases a preponderating mass of oxidized lead ores, such as cerussite, anglesite, and leadhillite, in which nests and nodules of undecomposed galena occur. Associated with these are : in Eureka, Nevada, arseniate of iron and arsenical pyrites, hydrated oxide of iron, quartz, and calcareous clay ; in Little Cottonwood Canyon and American Fork, Utah, iron oxide, and in some cases a combination of antimony, the nature of which I have not ascertained; also dolomite and quartz in widely varying proportions; in Bingham Canyon, Utah, only quartz and comparatively little oxide of iron, or iron sulphurets; in Cerro Gordo, California, oxide of iron, iron pyrites, antimonial compounds, copper ores, and, as gangue, carbonate of lime and quartz. In Argenta, Montana, occur, besides the above-named lead ores, pyromorphite, and molybdate of lead. The preponderating gangue of the Argenta ores is quartz, and there is here a larger proportion of galena than elsewhere in the West. In most of the localities named, the lead ores themselves contain sufficient silver to render its separation from the ore the main object of the smelting; but in some of the districts, and especially in Montana, the lead ores serve only to furnish the extracting agent for the silver of true quartzose silver ores, which at the same time contain a sufficient percentage of lead to make amalgamation impracticable. They are therefore beneficiated by smelting, although the lead itself has no market value.

Jan 1, 1873

By O. W. Ellis

THE writer has dealt with the effect of various methods of melting copper upon the gas content of the metal.1 The copper referred to in his in his earlier paper was melted in the foundry both in the oil furnace and the electric furnace. As the metal, did not measure up to conductivity FIG. L -INGOT OF OVERPOLEP COPPER. standard, the term "casting copper" was applied to the material in the title of the paper. It was thought that some information in regard to the gases in a sample of overpoled copper might also be of interest, and through the courtesy of C. R. Stevens, superintendent of the copper mill of the Westinghouse Elec. & Mfg. Co., such a sample was obtained. The metal was chill-cast in the form of an ingot about 7 in. long, 2 ½ in. deep (from the base to the raised surface of the ingot) and from 1 3/8 to 1 7/8 in. wide. A photograph of part of the ingot is shown in Fig. 1. The effect of overpoling on the surface of the metal is here quite clearly shown.

Jan 1, 1929

By A. J. Hendron, D. U. Deere, F. D. Patton, E. J. Cording

In the design of structures founded in the near-surface rock, a distinction may be made between those problems that are related to the strength of the rock mass, and those that are related primarily to the compressibility of the rock mass. The mining engineer deals almost exclusively with problems involving strength in the design of open-pit slopes and underground openings. The civil engineer is similarly concerned with strength problems in the design of vehicular and water tunnels; underground power plants; cut slopes in rock for highways, canals, and spillways; and in the study of the sliding resistance of the foundations of gravity dams and the abutments of arch dams. Moreover, the civil engineer encounters problems in which the compressibility of the rock becomes the key element in the design. These problems include settlement of heavy structures supported on rock, deformation of the abutments of arch dams, and deflection of pressure tunnel linings. The design problems listed above are still solved largely on the basis of experience and rule-of-thumb. However, recent developments in rock mechanics give promise of providing more realistic approaches to certain aspects of the design. This paper, presents some of the more important recent developments which contribute to an understanding of rock behavior and which aid in design of rock structures. Typically, four steps are involved in the design of a structure, whether it be a machine element, a structural member of a building, or a structure in rock. These steps are listed below:

Jan 1, 1967

By William B. Phillips

The possible sources of potash salts in the United States have been considered from many points of view during the last several years, but it is only within the last two or three months that the situation has become acute. We import from Germany, the only sourcc of large supply, more than $10,000,000 worth of potash salts annually, and this business has been badly crippled by the European war. If there was ever a time in our industrial existence when the necessity of providing for our own needs was more acute than it is now, we are not aware of it. One has only to study the price lists of chemicals sent out by the large supply houses to see the change wrought within a very short time. Whether or not these prices are to maintain for a considerable time, no one can say; but it appears to be probable that we shall not see prices materially lower for a period of uncomfortable length, to say the least. It is not my purpose at this time to discuss the various sources of supply of potash salts that have been suggested or recommended. Some of them might afford a pleasing relief but all of them combined would not affect the situation seriously. If we are to have our own sources of potash salts, they will have to compare, in some efficient manner, with the sources upon which we have drawn during the last 20 or 30 years; i.e., they must exist in minable quantities. It seems to me to be quite idle to speculate upon our domestic sources of potash if those sources are not of a character similar to those upon which we have so long depended. A few thousand or, perhaps, a few hundred thousand dollars' worth of chemically derived potash may be produced under the stress of present conditions, but when we consider that each year demands more than $10,000,000 worth, we must look to underground sources; we must look to mines similar to the famous Stassfurt and Halle deposits. If we cannot mine potash salts, we shall have to do without them for a while.

Jan 1, 1915

By C. R. Swarts

The use of compressed air or gas in oil wells for raising crude oil to the surface has, within the last year, become a dominant factor In production engineering. Previous application of this principle was largely confined to oil wells that had been pumping for a considerable length of time. In the Seminole area, the gas-air lift has been applied to wells imniediately after natural flow has ceased and in some cases while the wells were still flowing. This early application of the gas-air lift has been watchcd with intense interest by the petroleum industry, both with respect to methods of application and mechanical installations and to the effects on immediate and ultimate production. Methods of Application The Seminole pool at its inception contained sufficient gas associated with the oil to cause natural flow. As no frce gas was found in the main productive horizon, the Wilcox sand, all the gas present was dissolved in the oil, hence the natural flowing life was short, rarely lasting over 45 days. When natural flow ceased, high fluid levels were common, and as depth and crookedness of holes were obstacles to efficient pumping, the gas-air lift was used almost exclusively in raising the oil to the surface. Because of the high gravity of the oil, 41" A. P. I., and its high gasoline content, and also because of the desire to obtain production before offset wells became productive, quantity of production was the aim of the operators and a method of flow was used whereby this aim could be fulfilled. One of the outstanding features of this method consisted in flowing the wells through the annular space between the tubing and rasing. By this means a greater quantity of fluid could be handled than by flowing through the tubing of the size in ordinary use. Wells that would produce only a few hundred barrels on the pump were by this rnethod made to produce as high as 7000 bbl. on the lift. A few days or wreks of production at that rate meant a large recovery of oil. Casing of 636 in. diameter was commonly used as a production string with a 5 3/16-in. liner set on top of the oil sand. Upset tubing for irtro-

Jan 1, 1928

By Etienne A. Ritter

The Evergreen mine, located at Apex, in the northern part of Gilpin county, Colorado, has opened a very peculiar and interesting copper-deposit, in which both bornite and chalcopyrite occur as rock-minerals. The country-rocks are crystalline schists cut by dikes of granu-lite and of pegmatite. At the Evergreen property they have been cut by a dike of a uew kind of eruptive rock, to which I have given the name " Evergreenite." The rock is composed of quartz, alkali feldspars, orthoclase and albite (often interlocked as microperthite), with augite of the ægirine variety and long needles of enstatite and diallage. For reasons stated below, I believe the dike to be of Tertiary age. It is easily traced on the surface of the ground, from a point in the bottom of Pine creek, about a mile below Apex, to the top of Nevada hill, 1,500 ft. beyond and 600 ft. above it. (See Fig. 1.) It varies from 3 to 12 ft. in width, and is bounded on both sides by contact-zones about 60 ft. wide, in which the crystalline schists have been changed into pseudo-quartzites or pseudo-gneisees, according to the injection of an excess of quartz or of feldspars through the special layer of the schists. The most interesting feature is the presence of the pyroxenes, which are always found, though in very variable proportions from place to place, in the layers of these metamorphosed crystalline schists. The dike has torn from its walls a large number of fragments of the wall-rock. It must have been in a viscous state when that happened, because these fragments of the wall-rock do not show any sign of resorption or of assimilation by the magma. In places they are so distinct and so numerous that the rock looks to the naked eye like a pseudo-breccia, of which, never-

Jan 1, 1908

By Walter R. Hibbard, Walter L. Finlay

INTRODUCTION THE key feature of the lattice coherency theory of precipitation hardening1-6 is the forced coherence between matrix and precipitate which elastically strains both lattices and is believed to be the major source of strengthening in precipitation hardening. In systems exhibiting age hardening, the atom movements leading to precipitation are not at all extensive and are such as to require the minimum amount of energy to produce the interface; that is, the new lattice forms in such a way as to be as nearly as possible a continuation of the old with a matched, coherent plane at the interface at least during the initiation of the precipitation. The crystallographic sequence whereby regions of the matrix change to the precipitate lattice usually can be resolved into a set of shearing operations.5,6 Conversely, the perhaps novel speculation is made that solution of a second phase is accompanied by shearing movements which are possibly the reverse of the precipitation shearing movements. A basic premise of the investigation reported in this paper is that precipitation and solution shearing movements constitute structural weaknesses which might cooperate with applied stresses to facilitate plastic deformation. Another basic premise of the investigation is that the application of hydrostatic pressure to a precipitation hardening system will significantly alter the degree of disregistry across the matrix-precipitate interface and thereby significantly affect the course of age hardening. Two binary precipitation hardening systems were investigated: 12 pct zinc in aluminum which undergoes transformations, both precipitation and solution, by a simple crystallographic mechanism; and 4 pct copper in aluminum which undergoes a complex transformation in precipitating and dissolving a second phase. The effects of the application of uniaxial tensile creep stress during elevated temperature aging of both systems and of hydrostatic pressure during the elevated temperature aging of 12 pct aluminum-zinc were then investigated. Previous Investigations Van Wert in 1935,7 studied the effect of hydrostatic pressure on the room temperature age hardening of a few precipitation hardening systems. The latter were rather unfortunately selected since none is known to exhibit any marked volume change on aging and the majority were complex commercial alloys the precipitation mechanisms of which are not known. Jenkins, Bucknall and Jenkinson,8 in 1944, applied tensile creep stresses to a complex coppernickel-silicon alloy at various temperatures. The complexity of the alloy and the industrial objective of the work did not permit an appreciable addition to the theoretical understanding of either deformation or precipitation hardening.

Jan 1, 1948

By Thomas S. Lovering

Hot springs, geysers, steam-emanating fumaroles- these creatures of nature were until recently little more than geological curiosities, but today they are exciting the interest of engineers around the world for it has been shown that such hyperthermal areas can be profitably harnessed by man to provide heat and power for his communities. Although water from hot springs was used centuries ago to heat some Korean dwellings, is being used today by one-third of Iceland's population for similar purposes, and is finding industrial applications in New Zealand and elsewhere, the most dramatic use of geothermal energy has been its conversion into electricity. The largest installation at the present time is that at Larderello, Italy, where the Count of Larderello began to experiment in the production of electricity from geothermal steam in 1904. Eight years later after a quarrel with the local power company, the Count installed his first steam turbine, a unit of 250 kw capacity.

Jan 9, 1965

To THE BOARD OF DIRECTORS AND MEMBERS OF THE AMERICAN INSTITUTE OF MINING AND METALLURGICAL ENGINEERS. GENTLEMEN Like every other significant activity in the United States today, the work of the Institute has been affected by and adjusted to the prosecution of war against Germany, .Japan and their satellites. As the elaborate engines and materiel of modern mobile warfare are made, for the most part, of metals and other minerals; and are powered by mineral fuels, the industries -represented by the A.I.M.E. are of primary and vital importance. Of some 29 critical materials officially listed by the War Production Board, 24 are minerals. An alternate for one of the others, rated as a nonmineral, is to be made principally from petroleum. This alludes, of course, to rubber. The procurement of tremendous quantities of such raw materials and the effective processing, fabrication, and utilization of them depend on members of those branches of the engineering profession represented by the A.I.M.E.

Jan 1, 1943

By J. H. Pratt

In a recent paper* on the origin of corundum associated with the peridotites of North Carolina, attention was called to the constant occurrence of the mineral, chromite, in these rocks. The field-data obtained during the preparation of that paper have been used largely in the present paper. During the past summer the general occurrences of chromite have been carefully studied, and those in North Carolina have been especially examined in the field. It is purposed to give, in this paper, the reasons why the chromite should be regarded as having been formed at the same time with the peridotites, having been held in solution by the molten mass of the peridotite, and crystallizing out among the first minerals as the mass began to cool. This theory is essentially the same as that advanced by me for the origin of the corundum associated with the peridotite rocks, and a similar line of reasoning has been used to substantiate the theory proposed. Investigations concerning the igneous origin of some of the ores have been materially aided, during recent years, by the skillful experiments of Morozewicz and Lagorio,§ and by researches that show us, more clearly, why we should regard a fused mass of rock as a liquid, having similar properties to an ordinary solution. These experiments have shown that a molten basic glass, similar in composition to the basic magnesian rocks, dissolves alumina readily, and that upon cooling, the first minerals to separate out are corundum and spinel.

Jan 1, 1900

By J. D. Embury, R. M. Fisher, A. S. Keh

An investigation of the defect structure and properties following large strain deformation has been carried out using transmission electron microscopy and mechanical testing for a range of ferrous materials and for copper. It is shown that, for a variety of ferrous materials, a cellular substructure is developed during the initial stages of working and on further deformation the dimensions of this substructure are reduced. Quantitative measurements of the flow stress and the scale of the substructure indicate that the strength of heavily worked materials is largely determined by the spacing of cell walls. These cell walls act as dislocation barriers in a manner analogous to grain boundaries. FCC materials do not harden as extensively as bcc after cold working and the present observations on copper indicate that the dimensions of the substructure in fcc materials are not markedly reduced on deformation. The differences between the fcc and bcc structures produced by large plastic strains are ascribed to differences in the extent of dynamic recovery. It is tentatively proposed that the greater stability of substructural barriers in bcc structures results from strong interstitial Pinning effects. It is proposed that for large plastic strains the work-hardening process may be considered in terms of the reduction of substructural-barrier spacing during the working process. This pvovides a simplified hut useful analysis of the strain hardening occurring during mechanical processes. THE mechanisms of strain-hardening processes have occupied the attention of numerous investigators over the past three decades and a multitude of theories have emerged in this field. The majority of previous work has been concerned with the development of a description of the plastic behavior of single crystals in terms of dislocation theory.'" In contrast, scant attention has been given to the strengthening mechanisms operative during mechanical working processes such as rolling and drawing. The large plastic strains involved in these processes make it difficult to correlate the observations with any elementary dislocation theory. Further, as Bullen and coworkers3 have opined, for large plastic strains both hardening and recovery occur simultaneously and thus it is extremely difficult to estimate the effect of plastic strain on the ambient internal stress field. It is probable that for large plas- tic strains any theoretical estimate of the internal stress field must be made in terms of complex dislocation groups. Although some valuable theoretical work has been done toward calculating the elastic properties of dislocation groups4 any detailed self-consistent model for large plastic strain is as yet impossible. With these limitations in view it is still of value to examine the mechanical properties of highly strained materials as a function of their substructure. This relationship is explored in the present communication for a variety of materials subjected to rolling, drawing, or swaging. The primary object of this investigation has been to establish the validity and the limitations of the substructural strengthening mechanism proposed by Embury and eisher' for drawn pearlitic wire and by Meieran and Thomas for drawn tungsten wire. No attempt has been made to delineate the basic interaction mechanism which occurs between a slip dislocation and the substructure and the authors believe that a great deal more experimental evidence must be compiled before these fundamental aspects can be explored. Also, no specific attention has been given to the detailed formation of substructure during working. Experimental Details. A variety of materials were used in this investigation, the compositions and heat treatment of which are tabulated in Table I. The commercially pure iron is referred to throughout this report as Ferrovac E. The mechanical working processes were all performed at room temperature. The wire drawing was performed on a manual drawing bench. Reductions of between 10 and 20 pct in area per pass were used in both swaging and drawing. The experimental parameter used to evaluate the mechanical properties of the materials was the 0.2 pct proof stress. This was determined for wire samples using an Instron tensile machine at a crosshead speed of 0.02 in. per min. The techniques for preparation of samples for transmission electron microscopy have been described previo~sl~.~ Specimens from wire samples were prepared from longitudinal sections and in some cases from transverse sections. To evaluate the substructural characteristics of rolled materials, thin foil samples were prepared of both the face and edge sections. Results. One of the more familiar ways of expressing work hardening in mechanical working is by the flow stress as a function of reduction in cross-sectional area. Fig. 1 shows such a plot for Ferrovac E eutectoid carbon steel and for copper. The curve for Ferrovac E is characterized by an initial stage of rapid work hardening and a final stage of rapid work hardening separated by an intermediate stage with a low rate of work hardening. This behavior is typical of many ferrous materials and the drawn pearlite wire previously investigated by Embury and Fisher is a more pronounced example. Copper shows an initial

Jan 1, 1967

By F. M. Lewis, J. F. Myers

The selection of the proper type of flotation machine involves the consideration of a wide variety of factors. Under any condition, all types of machines will promote some kind of separation. Obviously, the correct way of deciding which type of machine is best suited for a particular problem would be to set up all types of machines and test them out in a competitive manner, but the vast number of small concentrating plants are unable to make such complete and exhaustive tests. The experience of the authors of this paper indicates that if all the factors involved in any particular problem can be determined, and if all the flotation-machine characteristics are understood, some basis for selection could be arrived at other than actual comparison. This paper is presented to show how the process factors and machine characteristics have been combined at the mills of the Tennessee Copper Co. from studies of several types of flotation machines. At the two mills of the Tennessee Copper Co. in the Ducktown Basin of Tennessee, four distinct flotation separations are made on the complex sulphide ore. Three different concentrates are produced from the ore—in the order of their importance: iron concentrate, copper concentrate, and zinc concentrate. Four different types of flotation machines are used. The selection of these four machines, for the plant operation, was based upon the study and operating experience of the machine units shown in the following list: Fagergren machine; square cell, size 56 inches Fagergren machine; level type, size 56 inches Denver machine; conical disk impeller, size 24 inches Denver machine; receded disk impeller, size 24 inches Minerals Separation Sub-A, size 24 inches Munro-Pearse deep cell, pneumatic Southwestern air machine, Hunt principle To date the study of flotation machines has been confined almost entirely to the rougher circuits. The various cleaning operations, being relatively a much simpler matter, have not been investigated so thoroughly. Table I shows a typical analysis of the two ores as well as of the mineral content.

Jan 1, 1947

By J. F. Myers, F. M. Lewis

The selection of the proper type of flotation machine involves the consideration of a wide variety of factors. Under any condition, all types of machines will promote some kind of separation. Obviously, the correct way of deciding which type of machine is best suited for a particular problem would be to set up all types of machines and test them out in a competitive manner, but the vast number of small concentrating plants are unable to make such complete and exhaustive tests. The experience of the authors of this paper indicates that if all the factors involved in any particular problem can be determined, and if all the flotation-machine characteristics are understood, some basis for selection could be arrived at other than actual comparison. This paper is presented to show how the process factors and machine characteristics have been combined at the mills of the Tennessee Copper Co. from studies of several types of flotation machines. At the two mills of the Tennessee Copper Co. in the Ducktown Basin of Tennessee, four distinct flotation separations are made on the complex sulphide ore. Three different concentrates are produced from the ore—in the order of their importance: iron concentrate, copper concentrate, and zinc concentrate. Four different types of flotation machines are used. The selection of these four machines, for the plant operation, was based upon the study and operating experience of the machine units shown in the following list: Fagergren machine; square cell, size 56 inches Fagergren machine; level type, size 56 inches Denver machine; conical disk impeller, size 24 inches Denver machine; receded disk impeller, size 24 inches Minerals Separation Sub-A, size 24 inches Munro-Pearse deep cell, pneumatic Southwestern air machine, Hunt principle To date the study of flotation machines has been confined almost entirely to the rougher circuits. The various cleaning operations, being relatively a much simpler matter, have not been investigated so thoroughly. Table I shows a typical analysis of the two ores as well as of the mineral content.

Jan 1, 1947

By R. H. Brown, F. Keller

Because of the extensive use of Alclad 24s alloy sheet in aircraft construction, there is much interest in the metallurgical changes caused by heat-treatment of this product.1, 2 One of these changes is the result of the diffusion of soluble elements from the core into the coating during treatment. This paper deals with the thermal treatments that may influence diffusion and with the practical effects of diffusion on the serviceability of the product. As is well known, Alclad 24s-T sheet has a core of high-strength alloy combined with surface layers of relatively pure aluminum. The microstructure of a cross section of this product is shown by Fig. I. Not only does the relatively high-purity coating have a high resistance to corrosion, and hence serves as a mechanical barrier between the core metal and the corroding environment, but in addition this coating exerts electrochemical protection over areas where the core may be exposed, such as cut edges. In addition, the coating affords electrochemical protection to projecting heads of A17s-T, 17s-T and 24s-T rivets, or attached members made from these alloys. Under some conditions of heat-treatment, however, diffusion of copper into the coating will alter the electrochemical relationship between the coating and the core to the extent that only partial protection will be obtained under some corrosive conditions. The reason for the electrochemical protection lies in the fact that the coating layers of pure aluminum are anodic to the alloy core. The addition of copper to aluminum produces alloys in which the potential is lower than that of the pure metal. Moreover, as the amount of copper in solid solution in 24s alloy is increased, the potential of the alloy becomes more cathodic. When heat-treated at 920°F. and quenched in cold water, 24s-T is about 0.16 volt cathodic to pure aluminum. However, copper will diffuse from the core into the coating, and if it reaches the surface the potential will be altered in a cathodic direction. Thus the potential difference between the core and coating may be less than 0.16 volt, depending uponIthe thickness of the coating, and the time and temperature of heat-treatment. Of the methods available for determining the extent of diffusion of copper from the core into the coating of Alclad 24s-T, two are generally used; namely, the metallo-graphic and the solution potential methods.3 Metallographic Methods Metallographic methods will reveal the progress of diffusion of copper into the coating. For instance, the diffusion zone in the coating intermediate between the coating surface and the core is shown in Fig. I. This photomicrograph is of a polished and etched cross section of 0.040-in. Alclad 24s-T sheet. Diffusion proceeds into the coating more rapidly along the grain boundaries than through the body of the grains. Consequently, the diffusion zone is not of uniform width

Jan 1, 1944

By F. Keller, R. H. Brown

Because of the extensive use of Alclad 24s alloy sheet in aircraft construction, there is much interest in the metallurgical changes caused by heat-treatment of this product.1, 2 One of these changes is the result of the diffusion of soluble elements from the core into the coating during treatment. This paper deals with the thermal treatments that may influence diffusion and with the practical effects of diffusion on the serviceability of the product. As is well known, Alclad 24s-T sheet has a core of high-strength alloy combined with surface layers of relatively pure aluminum. The microstructure of a cross section of this product is shown by Fig. I. Not only does the relatively high-purity coating have a high resistance to corrosion, and hence serves as a mechanical barrier between the core metal and the corroding environment, but in addition this coating exerts electrochemical protection over areas where the core may be exposed, such as cut edges. In addition, the coating affords electrochemical protection to projecting heads of A17s-T, 17s-T and 24s-T rivets, or attached members made from these alloys. Under some conditions of heat-treatment, however, diffusion of copper into the coating will alter the electrochemical relationship between the coating and the core to the extent that only partial protection will be obtained under some corrosive conditions. The reason for the electrochemical protection lies in the fact that the coating layers of pure aluminum are anodic to the alloy core. The addition of copper to aluminum produces alloys in which the potential is lower than that of the pure metal. Moreover, as the amount of copper in solid solution in 24s alloy is increased, the potential of the alloy becomes more cathodic. When heat-treated at 920°F. and quenched in cold water, 24s-T is about 0.16 volt cathodic to pure aluminum. However, copper will diffuse from the core into the coating, and if it reaches the surface the potential will be altered in a cathodic direction. Thus the potential difference between the core and coating may be less than 0.16 volt, depending uponIthe thickness of the coating, and the time and temperature of heat-treatment. Of the methods available for determining the extent of diffusion of copper from the core into the coating of Alclad 24s-T, two are generally used; namely, the metallo-graphic and the solution potential methods.3 Metallographic Methods Metallographic methods will reveal the progress of diffusion of copper into the coating. For instance, the diffusion zone in the coating intermediate between the coating surface and the core is shown in Fig. I. This photomicrograph is of a polished and etched cross section of 0.040-in. Alclad 24s-T sheet. Diffusion proceeds into the coating more rapidly along the grain boundaries than through the body of the grains. Consequently, the diffusion zone is not of uniform width

Jan 1, 1944

By Persifor Frazer

At a time when all those interested in the iron trade are carefully scanning the horizon for new sources of the raw material, a few words concerning a field, which though not new, has not been hitherto fruitful of statistical information, may be deemed appropriate at this meeting. The district alluded to is the belt of the Middle James River, or in other words, that portion of the ferriferous belts of Virginia lying between Josua Falls and the little settlement of Norwood, in the counties of Amherst and Nelson, and on the left bank of the James River. This region shows unmistakable signs of developing a very considerable market for iron ores and for iron in the future, as well as a tempting appearance of possible productiveness in the former. It, is extremely hazardous to deal in generalizations as to the productiveness or non-productiveness of these measures without a more thorough development than has yet been attained. It is true that they probably constitute an horizon whence comes a part of the marvellous mineral wealth of the northern peninsula of Michigan. But

Jan 1, 1883

By Charles S. Barrett

The experiments reported in this paper have been fruitful in disclosing the mechanism of the deformation of iron in compression. They have established the nature of "deformation bands," "etch bands," or "X-bands," that have been a recognized but little understood feature in the structure of cold-worked metals since the early days of metallography, and have shown the role of the bands in the development of preferred orientations by cold-working. The work has also shown the relation of the orientation of individual grains to the preferred orientation of the aggregate. Some of the methods previously used in the determination of the indices of slip planes and slip directions are shown to be untrustworthy in the presence of deformation bands. The conclusion is reached that many slip planes and slip directions must operate during each stage in the compression of a single crystal, and that theories failing to take account of this require revision. In conducting the experiments a method of compression has been used by which extreme reductions can easily be reached, even to the limit set by the metal's capacity to deform without fracture. The work is a portion of a research program on the plastic properties of iron and steel. It is being used as a foundation for studies of orientntions resulting from recrystallization and is being extended to other metals and other types of deformation. Previous Work The previous experiments are few and have given confusing results Onol compressed a polycrystalline alpha-iron specimen between two flan plates of a testing machine and found that severe deformation oriented the crystals into a duplex preferred orientation, one set of crystallites having a cube diagonal of the body-centered cubic lattice parallel to the compression axis, and another set having a cube axis parallel to the compression axis. We shall speak of this structure as a double fiber texture of the type [111] + [100]. Wever2 also made an X-ray determination of the texture

Jan 1, 1939

By Charles S. Barrett

The experiments reported in this paper have been fruitful in disclosing the mechanism of the deformation of iron in compression. They have established the nature of "deformation bands," "etch bands," or "X-bands," that have been a recognized but little understood feature in the structure of cold-worked metals since the early days of metallography, and have shown the role of the bands in the development of preferred orientations by cold-working. The work has also shown the relation of the orientation of individual grains to the preferred orientation of the aggregate. Some of the methods previously used in the determination of the indices of slip planes and slip directions are shown to be untrustworthy in the presence of deformation bands. The conclusion is reached that many slip planes and slip directions must operate during each stage in the compression of a single crystal, and that theories failing to take account of this require revision. In conducting the experiments a method of compression has been used by which extreme reductions can easily be reached, even to the limit set by the metal's capacity to deform without fracture. The work is a portion of a research program on the plastic properties of iron and steel. It is being used as a foundation for studies of orientntions resulting from recrystallization and is being extended to other metals and other types of deformation. Previous Work The previous experiments are few and have given confusing results Onol compressed a polycrystalline alpha-iron specimen between two flan plates of a testing machine and found that severe deformation oriented the crystals into a duplex preferred orientation, one set of crystallites having a cube diagonal of the body-centered cubic lattice parallel to the compression axis, and another set having a cube axis parallel to the compression axis. We shall speak of this structure as a double fiber texture of the type [111] + [100]. Wever2 also made an X-ray determination of the texture

Jan 1, 1939