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By Pablo Hadzeriga

Great Salt Lake brine was subjected, in laboratory scale, to conditions simulating solar evaporation. Solid phases and the variation in composition of the liquid phase throughout the potassium salts crystallization zone are presented. These experimental results are discussed and compare with stable equilibrium data of the quinary system Cl-, SO4, Na+, K+, Mg + + and H2O. The Great Salt Lake brine in Utah is a vast reserve of several potential chemicals which has attracted much attention in the recent past. From the standpoint of an ore reserve, it may be said that the lake contains a low grade ore which has to be concentrated by evaporation of water. Because of the fairly favorable weather conditions in the Great Salt Lake area, it seems reasonable to consider solar evaporation as an economical means of concentration. From the view of phase chemistry, the main constituents of Great Salt Lake brine make it belong to the five component system: C1-, SO4=, Na+, K+, Mg++ and H2O. Because of their low concentration, the presence of other elements may be regarded as having little effect on the equilibrium of the five main components. Equilibrium data for the quinary system of our interest has been available for many years. Using these data, it is possible to calculate how the brine of the lake will concentrate when subjected to solar evaporation. In practicing solar evaporation, the weather factor and supersaturation conditions cannot be ignored, but their introduction into calculations using equilibrium diagrams is almost an impossible task. With the experimental work presented in this paper, an attempt is made to compare the stable equilibrium data of the quinary system as applied to the case of the Great Salt Lake brine and the dynamic equilibrium when that brine is subjected to continuous solar evaporation. Sea water brine belongs to this quinary system when only the major constituents are considered. The study of this system has been carried on since the last decades of the nineteenth century. The reason for these intensive studies was to give a geological explanation to the underground potash deposits. AS a result, many theories were presented trying to relate the equilibrium data with the geological formation, paragenesis and metamorphism of these deposits. Two main approaches were followed for the equilibrium studies of this quinary system. One of them, and the best known to us, was the school started in Germany in the last century by J. H. Van't Hoff. The other one, which started about the same time, was the school of N. S. Kurnakov in Russia. Both approaches were different and as a consequence generated opposite theories about the geological formation of potash deposits. The Van't Hoff school studied the quinary system of sea water under careful laboratory control, resulting in stable phase diagrams. During these studies, Van't Hoff recognized the difficulties in crystallizing some double salts.' ". . . . we unexpectedly found that some compounds whose formation in the solutions under investigation was possible at 25°C, nevertheless totally failed to put in an appearance. These, not to mention the calcium salts, were leonite, MgSO4 . K2SO4 4 H2O; kainite, KC1-MgSO4 . 3 H2O; and kieserite, MgSO4 .H2O. Even exceedingly slow crystallization with the addition of the compounds themselves did not remove the condition of supersaturation in the case of these bodies." However, those salts (leonite, kainite, and kieserite) were included in the stable phase diagram at 25°C as shown in Fig. 1 using D'Ans data.3 The figure also shows the sequence of crystallization of the Great Salt Lake brine according to the stable diagram. In later studies by the Van't Hoff school, especially by D'Ans,3 Karsten,4 Autenrieth,5,6 attention

Jan 1, 1968

By G. M. Schwartz

THERE has been considerable controversy regarding the structure and mineral constituents produced when iron ore is sintered. This investigation was undertaken in order to establish the fundamental reactions that take place in the sintering process by determining the nature of the resulting minerals. The writer's immediate interest in the subject arose mainly from the request of E. W. Davis for information based on a microscopic study of sinter submitted by him in May, 1926. In the author's preliminary work, samples of iron-ore sinter were secured from the Minnesota School of Mines Experiment Station and from commercial plants. These were polished by the usual methods for polishing opaque ores. In order to study these surfaces satisfactorily, it is necessary to magnify them rather highly, a range from 100 to 1000 dia. being used. For the higher magnifications oil-immersion lenses and an intense source of light are necessary. After the preliminary study had shown the problems involved, a series of small samples were sintered under carefully controlled conditions and with analyzed materials. Variations in the relative amounts of ore, coal and water were made in order to study the effect of each constituent. The attempt has been to arrive at a clearer understanding of the sintering process and the reactions involved without reference to any preconceived notion as to sinter. It is clear that the study of polished surfaces has yielded results not possible with thin sections alone. The thin sections made in this work were found unsatisfactory at magnification greater than 75, whereas magnifications of 1000 were easily studied with reflected light on carefully polished surfaces. A rather complete statement of observed facts is made so that the reader may form his own conclusions. The writer's interpretations are suggested.

Jan 1, 1929

By Samuel Gibson Frantz, G. W. Jarman

The purpose of this paper is to relate briefly the development of magnetic separation and its extension from the separation of iron into its present use in the nonmetallic field, to suggest possible future extensions of its field of usefulness and its possible cooperation with other separating methods. The engineering design of separating machines, and statistics as to the number of machines in operation, types, their location and production are outside the scope of this paper. Specific data will be given, however, on certain selected applications. A large part of human endeavor consists in separating one thing from another; the good from the bad, the desired from the undesired. In fact, a philosopher might plausibly claim that separating things into categories and choosing between them is the object of thought itself. In dealing with matter, separation is nowhere more inherently necessary to attain our objects than in mining and metallurgy. Both our desire and our ability to make separations are results of the physical differences between things. Gross separations such as removing ore from worthless rock or coal from slate are usually made visually and depend upon form and color, which are physical properties. When the desired and the undesired things are intimately mixed, however, it becomes impractical to select visually even if the individual particles are readily recognizable to the eye, and some automatic way of making the particles separate themselves on the basis of their own inherent differences in physical properties must be resorted to. Some of the physical properties which have been used as a basis of separation are: color, shape, hardness, size, density, elasticity, surface propertics (surface tension in contact with liquids, etc.), electrical conductivity, dielectric constant, and magnetic susceptibility. Differences in these properties are used in the following methods of separation: color sorting, sifting, settlement in air and in liquids, float-sink methods, flotation, electrostatic and magnetic separation.

Jan 1, 1932

By J. B. Dilworth

The purpose of this paper is, first, to give a general account of a little-known coal-district of SE. Kentucky, its topography, drainage, and mineral resourcee, for those who may be interested in its economic development; and secondly, so to describe the geologic features of the field as to furnish available data to those engaged on the broader problems of Appalachian coal-geology. The data from which the major portion of the paper has been prepared were obtained, in professional investigations for private individuals and corporations, within the last decade. The area under review, defined by a heavy line on the map, Fig. 1, lies between Little Black and Pine mountains, and extends from Harlan on the west to a N-S. line crossing Looney creek 3 miles from its mouth on the east. This area can be divided for description into a Western and an Eastern Division. The character of investigatioil pursued in the Western Division, below Fugitt creek, was very different from that employed in the Eastern. In the former, only a rapid reconnois-sance was attempted: such coal-openings as had been made by prospectors or by citizens in obtaining fuel were visited, their

Jan 1, 1913

By Walter Miller

The focus of attention during 1939 was on increasing the octane number of gasoline. The "octane race" resumed full swing. The averagc octane number of house-brand gasoline by the end of the year had easily reached two numbers higher, with several companies in the field actually purveying house-brand gasoline of 78-80 "research" octane number, equivalent roughly to from 74 to 77 A.S.T.M. octane rating, compared with the 70 A.S.T.M. ceiling of two or more years ago. Whether this trend toward much higher octanes is the result or the cause of the many t,echnical developments in the motor-fuel field of recent, years, progress has really been startling. In addition to the advance in catalytic cracking and catalytic re-forming, other important contributions to the technical ability to produce higher octane values include: installat>ions involving increased capacity in thermal re-forming, with improved economic status both as to yields and octane number, by coupling with catalytic polymerization; more widespread adoption of catalytic and thermal polymerization, and a surge toward extensive installations of newly developed alkylation processes for making iso-octane, neo-hexanr and other high antiknock products; and greater use of improved desul-phurization processes, and application of superfractionation methods for segregation of practically pure hydrocarbons with superior octanr qualities from gas and highly volatilc liquids. The approaching of practical limits in the use. of tetracthyl lead (t,hr well-known "law of diminishing returnsn coming into the picture at the higher octane levels being approached) has given impetus to development of the methods listed above. In particular, processes that improve the octane rating and also increase ethyl lcad sc.nsitivity have had considerable study durirlg the year. CatSlytic Re-foRming Although the interesting report on the Houdry catalytic cracking process presented at the annual meeting of the American Petroleum

Jan 1, 1940

Jan 1, 1880

By W. F. Vietti

Operations in the Texas Gulf Coast during the past year have resulted in the discovery of a number of new fields arid the extension of a few of the older fields, both by deeper drilling and by lateral development. Twenty-six new oil and gas-producing areas and discovery of oil or gas in three subsequently abandoned wells have been recorded for a total of 29 new fields of varying importance. Producing areas at Conroe, Manvel, Greta, Pierce Junction, Hastings, Dirks, Thompson, Batson, Mykawa, Tomball, Raccoon Bend, Samfordyce arid Saxct have been increased. Primary geologic studies followed by geophysical mapping or straight geophysical prospects have been responsible for the more important discoveries. These methods have further proved themselves an aid to limiting wildcatting to the more prospective areas and as the chief means to discover reserves in the future. Production for 1935 totaled 69,560,720 bbl. as compared with 60,850,-360 bbl. for 1934. Strict proration has been in force throughout the discovery of more oil than has been produced. The number of producing oil wells has steadily increased to 4851 at the end of 1935, as compared with 3858 at the end of 1934, owing in part to the prolonged life, because of proration. There were 1272 oil and gas wells completed during 1935, as against 835 in 1934. New Fields Pertinent data on the new fields discovered during 1935 are includrd in Tables 1 and 2. Hence, the discussion of these discoveries will be limited. Bee County.—Three new gas fields were added during the year: Beeville, discovered by G. M. Church in No. 1 Wood on Sept. 21; Foley, discovered by Dirks Bros. in No. 1 Foley on Feb. 8; and Plummer, discovered by Hynes and Fisher in No. 1 T. M. Plummer on Sept. 2. The three new oil fields added are: Hartzendorf, drilled on fee land by Hartzendorf and completed on May 17 as a small pumper; Ray, southwest of Tuleta, and discovered by Jameson and Burns in No. 1 Campbell

Jan 1, 1936

By James P. Kimball

BY the term weathering of coal is meant the process of deterioration to which under various circumstances it may be exposed at ordinary temperatures, both from outward agencies on the one hand, and on the other hand from its own constitutional qualities. This process involves along with some minor qualitative changes certain quantitative changes resulting in a gradual and limited reduction in the quantity of the organic elements, and relatively a corresponding increase of its inorganic or mineral constituents as represented by its ashes, and often in an increase of the absolute weight of the coal. In common with many mineral substances, coal absorbs oxygen

Jan 1, 1880

By T. F. Bower, M. C. Flemings, H. D. Brody

A series of experiments are reported which show thai reasonable assumptions for analysis of solute redistribution in solidification of castings and ingols illclr(de: negligible undercooling before nuclcation of solid phases, negligible increase of solute in advance of the tips of growing dendrites, complete diffusion within the Liquid oer distances the order, of dentrite arm spacings, platelike dentrite t/o?$holog?.. Qzmli/ali,e and periment is obtained JOY Al-Cu alloys front measurements of amount of nonequilibrium second phase, minimum solute content at the centers dentrites arms (after solidification), and 3) change in minimum solute content in dentrite arms during solidification. In a previous paper' analyses were given describing solute redistribution in dendritic solidification. The analyses were undertaken primarily to permit prediction of "severity of microsegregation" in a casting or ingot after solidification and cooling to room temperature, but can also be used to predict "local fraction solid' as a function of temperature in the solidifying alloy. Numerical results were given for Al-Cu alloys. The aims of this paper are to examine the validity of some of the assumptions of that analysis, and to compare predictions of the theory with experiments. All experiments reported are on Al-Cu alloys, the bulk on Al-4.5 pct Cu alloy. EXPERIMENTS Experiments conducted were on small ingots, 41/2 in. in diam by about 10 in. high. solidified in a controlled thermal environment (i.e., in a resistance-heated, re-circulating air furnace, whose temperature could be controlled to 1°C). In one series of experiments, the ingots were solidified very slowly (solidification time was varied from 8 to 1000 hr) and at constant rate of heat extraction. In a second series of experiments the ingots were solidified ( 'unidirectionally". Fig. 1 is a sketch of the method of making the two different types of ingots. The unidirectionally solidified ingots were fully columnar, and the slowly solidified ingots had equiaxed structures, Fig. 2. In making the slowly solidified ingots, the mold employed was carbon steel, coated with inert refractory. Typically the mold and its environment were heated to 700°C. The molten alloy was then poured into the mold and the temperature of the system equilibrated above the liquidus. The environment of the mold was next cooled with a controller responding to a differential thermocouple that measured the difference between the temperature of the melt and the temperature of the mold environment. The differential thermocouple consisted of one chromel-alumel junction in the melt connected in opposition with a second junction in the furnace. The potential across the differential thermocouple was input to the controller which acted to keep this potential at a set. constant value; hence the temperature difference between the two junctions was maintained nearly constant. Major resistance to heat flow in the above apparatus was between the metal surface and the furnace atmosphere, not in the metal itself. By maintaining a constant temperature difference between the metal and the furnace atmosphere, the controller maintained an essentially constant rate of heat extraction during solidification, regardless of amount of heat released by the metal per unit temperature change. When the metal temperature dropped just below the eutectic temperature. the ingot was removed from the furnace and water-quenched. The unidirectionally solidified ingots were cast in a similar mold to the foregoing except that provision was made to extract heat through the bottom face of the mold by passing air or water through the mold base, Fig. 1. For these experiments, metal and mold temperature were again equilibrated above the liquidus. Temperature of the mold environment was then held

Jan 1, 1967

By B. B. Rath, Hsun Hu

Rates of migration of large-angle boundaries have been studied in zone-refined aluminum crystals, defonned 80 pct by rolling in the (110)[112] orientation at -78°C followed by a recovery anneal at 80°C. Artificially nucleated grains show a marked variation. by an order of magnitude, in their growth rates in different directions. The average activation energy for the migration of all boundaries was found to be about 16,000 cal per mole. The anisotropy of the boundary migration is rationalized on the basis of the boundary structure. It has been observed by Beck and HU,1 Kohara el al,2,3 and Czjzek and Haessner4 that recrystallized grains formed upon annealing Of deformed sing1e crystals of aluminum show anisotropic growth characteristics. Kohara et al. found that single crystals rolled in the (110)[112] orientation, when random nuclei were provided on one side of the crystal by rubbing with emery paper and annealing, developed a sharp recrys-tallization texture on the other side of the crystal upon further annealing. This sharp recrystallization texture consisted of four components, which were related to the deformation texture of the crystal, i.e. (110)[112], by rotations of ±40 deg around each of the two common [ 111] axes' They also noted that recrystallized grains were elongated in directions perpendicular to either of these two common [1111 axes. They attributed this anisotropic growth to the difference in the rate of self-diffusion or diffusion of impurity atoms along the tilt and the twist boundaries. A somewhat similar investigation was conducted by Czjzek and Haessner4 On strained single-crystal sheets Of alum- inum. These authors claimed that the matrix structure of the deformed crystal had a greater effect on the growth anisotropy of the recrystallized grains than did the boundary orientation itself. In the present investigation quantitative measurements of the rate of grain boundary migration in anisotropic growth have been made in zone-refined aluminum (99.9999+pct pure) crystals deformed 80 pct by rolling in the (110) 112] orientation. Crystals of this particular orientation were chosen because of the following desirable features: 1) the crystal does not change its orientation during rolling; 2) the rolling plane contains all the significant crystallographic directions; and 3) when annealed, following deformation, the crystal does not re-crystallize spontaneously but polygonizes to a stable and homogeneous structure. Hence, the initial orientation of the crystal and a constant strain energy in the matrix can be maintained during subsequent grain boundary migration studies. It is essential to keep the driving force constant for the study of boundary mobility.5 EXPERIMENTAL PROCEDURE A cylindrical single crystal of 1 in. diam was grown by the Bridgman method in a high-purity graphite mold. The resistance ratio, R(4.2°K) /R(298°K) , of the grown crystal was approximately 2.0 x 10-4. A number of slices, 1/4 in. thick, were cut from the crystal along the (110) plane and were mechanically and electrolyti-cally polished to remove the strained surface layer. The crystals were then rolled along the [112] direction to 80 pct reduction in thickness at -78°C. To minimize surface friction, the crystals were rolled between two layers of 0.005-in. teflon sheet. Rolling was interrupted, prior to completion, to remove the surface layers and the edges by electropolishing. These and similar precautions in handling the rolled crystals

Jan 1, 1967

By Wm. Terry Siemers, Frank E. Kottlowski, George S. Austin

The value of industrial rocks and minerals produced in New Mexico in 1978 exceeded $227 million. The state ranked first in the nation in production of potash and perlite and was a leader in pumice production. Other commodities with sizable production in New Mexico include barite, caliche, clay, dimension stone, fuorspar, gypsum, humate, limestone, mica, salt, sand and gravel, scoria, and silica sand. Non-metallic resources are distributed throughout the state, but development and exploitation is concentrated in western and southeastern New Mexico. The value of industrial rocks and minerals within the state grew about 9% to more than $227 million in 1978. Continued growth, however, depends on continued demand, exploration, and development.

Jan 1, 1982

By Hans Haalk

PRACTICAL or applied geophysics-as we designate the border region between physics and geophysics on one hand and practical geology on the other-has as its object the application of physical or geophysical methods of investigation to problems of practical geology. Its field of operation comprises all methods of physical measurement that are used in the problem of determining, from the geophysical influences of the subsoil that can be measured at the surface of the earth, the special characteristics of the association of strata, faults, etc., to detect the presence of deposits and to investigate underground structures. It therefore repre-sents an aid, a physical method of research in practical geology, and is inseparably connected with geological studies; for this reason, it is also called geophysical prospecting. Formerly research methods of practical geology were based on observation exclusively: first, on the observation of the strata and formations at accessible parts of the surface of the earth, especially in shafts, borings and mines if such were available; then on the observation of the tectonic conditions in so far as these were already known at places directly visible; and finally, by estimation of the importance of formations of the terrane. Later, there were added in special cases, analytical chemical crystallo-graphical, petrographical and similar investigations of rock samples which were taken from the places under consideration. The knowledge thus obtained is of value and is expanded by hypotheses and constructions that are supported by geological theories of origin and by laws of the sequence of formations and rock systems, which are based on long experience.

Jan 1, 1928

By Myrick N. Bolles

The concentration of gold and silver in mattes low in copper, and the subsequent separation and recovery of either or both of these metals, is a question the satisfactory solution of which has long vexed metallurgists. It covers a broad and important department of metallurgical science and brings in its train a series of attendant problems continuing from the initial operations of concentration to the final recovery of " values."

Jan 1, 1905

By R. P. Smith

THE carbon content of iron-silicon and of iron-manganese alloys at fixed activities of carbon has been reported previously.' It seemed desirable to investigate a system which allows a more extended range of alloy composition within a single phase region. The iron-nickel system is ideal in this respect, in that all alloys from 100 pct Fe to 100 pct Ni are face centered cubic ("austenitic") at 1000 °C. The experimental procedure was similar to that previously described.1,2 The alloys, in the form of pieces about 2 by 2 by 0.2 cm thick, together with a similar specimen of pure iron, were equilibrated with each of a series carbon monoxide-carbon dioxide tnixtures of fixed composition, quenched in the carburizing gas in the top of the furnace and then analyzed for carbon. The carbon content of samples containing more than 0.3 wt pct C was determined by the usual combustion method; those with less carbon

Jan 1, 1961

By H. E. McKinstry

Movement on a fracture of irregular shape can cause local widening of the fissure and thereby offer freer channelways for circulation of ore-depositing solutions. This influence: coupled with large areas of wall rock available for reacting with ore solutions in brecciated and shattered ground can account for locally active deposition of metals and the resulting ore shoots. Such irregularities in the fracture system may be caused by local variations in the strength of rocks and by pre-existing lines of weakness, especially if these stand at favorable angles to certain components of the fracturing stress. Therefore correct interpretation of the mechanics of fracturing should permit deductions as to structurally favorable places on unexplored portions of the vein system. Introduction It has long been recognized that movement on a curved or irregular fault surface is capable of separating the walls in certain portions of the fault, but until very recent years the importance of this mechanism as a factor in localizing ore shoots has escaped proper recognition. A short time ago W. H. Newhouse' presented a careful analytical study of displacements and their corresponding open spaces. For reasons that will be discussed later, it frequently happens that portions of the vein which are favorably oriented are not merely wider but also richer than the average. In many cases the widening with its accompanying richness coincides with very minor changes in the dip or strike of the vein, irregularities that commonly escape notice unless the vein is mapped in detail and a careful geometrical analysis made. While the relationship between the width of the vein and the changes in dip or strike has been recognized as a matter of observation, the irregularities have been accepted as more or less the result of accident. There has been very little effort except in isolated cases to find out the causes of these changes in dip or strike. Yet it is clear that if the causes can be recognized and expressed in terms of geologic structure the geologist will know where to look for repetitions of these favorable conditions either on extensions of the same vein or on adjoining veins. Any lack of understanding of the causes is due to the limitations of our ability to interpret our observations and not to the sheer capriciousness of

Jan 1, 1941

By H. C. Gatos, Ahmed Azzam

A UTORADIOGRAPHY would appear to be sim-A pler and less time-consuming for diffusion studies than any of the radioactive tracer techniques commonly employed, namely, the sectioning, surface increase, and surface decrease techniques.' Accord- ingly, it was felt worthwhile to investigate the applicability of autoradiography to self-diffusion measurements, and gold was chosen for this purpose. The radioactive isotope Au'!'' was used, as obtained from the Brookhaven National Laboratory. Its radiation consists of p (0.97 mev) and y (0.41 mev) rays, and it has a half-life of 2.69 days. No-Screen X-ray film was found suitable for these experiments: the film has the desired high speed for recording P rays and yet is practically insensitive to y rays. On the other hand, due to the high atomic weight of gold, this metal is a strong absorber for p rays. The

Jan 1, 1953

By T. A. Rickard

Among the gold-deposits discovered in recent vears none is more extraordinary in richness or interesting in structure than that of the famous mine at Mount Morgan. At a time when but few Australian mines were known to the world outside the colonies, Mount Morgan was quoted as an occurrence, unusual not only in its origin (for it was said to be dye to geyser-action) but also in the purity of its gold. The mine is situated just within the tropics, twenty-six miles southwest of Rockhampton, in central Queensland. Queensland attained in 1889 the first place among the gold-producing colonies of Australasia, a position previously always held by Victoria. In that year Queensland produced 737,822 ounces, while Victoria cape second with 614,838 ounces. Of the four chief mining districts Rockhampton stood first, as the following figures show: Quartz crushed, Yield,. Average per ton, Tons. Ounces. Oz. Dwt. Rockhampton ,....81,138 340,669 4 4 Charters Towers,.. .. 109,328 165,551 1 10 Gympie,.....106,625 112,847 1 1 Croydon,.....29,423 51,156 1 15 It should be added that Queensland has but little alluvial mining, the total output from this source in 1889 being only 5044 ounces, none of which came from the four principal gold-fields. Leaving out Rockhampton, the output of which is practically that of the Mount Morgan mine, it will be noted that the more northerly goldfields show the highest average (Gympie being furthest from and Croydon nearest to the equator). This is largely explained, however, by the increased cost of milling, due chiefly to the want of water for batteries and the consequent economical necessity of selecting high-grade material only for crushing. During the year ending November 30, 1889, the Mount Morgaq

Jan 1, 1892

By Austin E. Dwight

IT has been shown by Oelsen and Wever' that the effect of a solute element on the allotropic transformation in iron is dependent upon the quantity

Jan 1, 1957

By R. R. Van Valkenburch

IT has always seemed to me that mining methods are inventions that follow necessity. I have yet, to be connected with a property where the consultant who has been engaged has laid out a mining method that has been strictly adhered to through the life of the mine. Possibly there are exceptions. As a general rule, perhaps, the method becomes the result of sad experience. I suppose if a person were to attempt to measure the tendency to get away from shrinkage stoping, he would need to send out a questionnaire and expect to receive truthful answers, and, having compiled the results, I think we would find that throughout the country there would be but few cases where present value of product permits the old original so-called shrinkage method to be followed. The method that I had hoped to hear Mr. Fozard expound is strictly an adaptation of shrinkage. Cav-ings do not enter. It was developed by Mr. Fozard and his staff at the Beatson mine of the Kennecott Copper Corp., at, Latouche, Alaska. Stephen Birch, in the TRANSACTIONS in 1923, submitted a brief paper on the mining at Beatson. He stated that a new adaptation of shrinkage was being tried because, although at sur-face the copper .content had been relatively high, at lower levels, in the mine it had decreased.

Jan 5, 1927

By Robert E. Green, P. W. Kingman

Application of a constant geometry compression test to single crystals of aluminum of selected diameters from 1/4 to 1/64 in. showed the presence of a diameter-dependmt size effect. The most pronounced effects were found in those crystals oriented for single slip, while for specimens possessing orientations in the comers of the standard stereographic triangle virtually no size effect was exhibited. The yield stress of the crystals oriented for single slip was found to increase with decrease in specimen diameter, while the strain-hardening rate was found to be lower for the smaller specimens. The experimental results are in general agreement with those of other investigators obtained from lensile tests on copper and aluminum crystals. THE earliest systematic investigation of a possible size effect on the plasticity of metals was that of no,' who in 1926 performed tensile tests on cylindrical aluminum single crystals with diameters of 3 to 8 mm. Ono concluded that the gross stress-strain curve did not show a diameter dependence, but that the resistance to slip for strains of 0.1 pet and less appeared higher for 3-mm-diam crystals than for larger sizes. Later studies of aluminum by Maddin et al2 tentatively concluded that a size effect exists, but the conclusions were again open to question because of inconsistencies in the experimental data. Wu and Smoluchowski3 had previously shown that the slip system activated in a single-crystal sheet specimen of aluminum is a function of the specimen cross section in the slip direction, but no stress-strain data were obtained. Subsequently Fleischer and Chalmers4 studied the effect of the length of the slip direction of the primary-slip system on the stress-strain curve by testing aluminum crystals with geometrically dissimilar cross sections. In the course of this investigation a size effect was indicated in rather large crystals; however, the number of these tests was small. Other investigators have indicated that a size effect in aluminum is appreciable only for diameters of 0.5 mm or less.5, 6 Size-effect studies have also been carried out on copper crystals, the most detailed being that of Suzuki et a1.7 who performed tensile tests on specimens of many diameters ranging from 2 to 0.12 mm. Suzuki found a strong size dependence in the easy-glide region, both the extent of the easy glide and the hardening rate in easy glide were size-dependent, and the size effect was found to be orientation-dependent. Suzuki's results are in agreement with the less extensive observations of Pater-sonB and those of Garstone et al.9 A size effect was found by Rebstock using tubular copper crystals.'0 Size effects have also been noted in a brass,6, 11 in cadmium,12'19 and in hexagonal crystals.14 All the previously cited works have been entirely concerned with the variation of specimen cross section. The effects of specimen length and the change of specimen geometry which results from using progressively thinner specimens while maintaining the same specimen length have been largely ignored. A theoretical discussion of the effects of specimen length and geometry has been given by Hauser and Jackson,15 who predict a grip effect on easy glide as a function of specimen geometry provided that the specimen dimensions are large compared with the spacing between the slip bands, and by Fleischer and Chalmers,18 whose analysis of grip effects resulting from lattice rotation predicts an increase in easy glide with an increase in specimen length. A study of size and geometry effects in aluminum crystals by Kitajima and shimba17 indicated increasing amounts of easy glide in specimens of increasing length and identical cross section, and nearly identical stress-strain curves for specimens of different sizes having constant length-to-diameter ratios. Since the present study is primarily concerned with diameter dependence, the following factors were taken into account: specimen material, specimen geometry, testing method, range of sizes to be tested, and possible influence of surface and volume effects. Aluminum was chosen because of the present lack of conclusive results and the seeming possibility of size effects at relatively large diameters, the

Jan 1, 1964