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By H. F. Silliman, Daniel R. Hull, John R. Freeman

IN the normal operation of a brass-rolling mill, sheet and strip has, for the most part, been finished in comparatively thin gauges, involving a substantial amount of coldwork and a considerable number of anneals. This condition has been disturbed by the prep0nderance of cartridge brass, which is not rolled to thin gauges, and particularly by brass for artillery cartridge cases, on which the mill may finish its work at a thickness between 0.400 and 0.900 in. Obviously, the amount of rolling and the number of anneals to which such a product can be subjected are small compared with strip that is carried to a thickness of a few hundredths of an inch. As a result, critical examination into the internal condition of metal has been made on an extensive scale at a stage of manufacture that would not, in normal times, have been chosen for complete inspection. Under these conditions, a type of defect has been recognized that is not seen at thinner gauges. It might be more accurate to call it the appearance of a defect, since it refers to an apparently laminated, discontinuous structure, which, in fact, does not exist as such, and disappears after suitable treatment. For this reason it has been called a phantom lamination, which the authors consider an appropriate term. It is the purpose of this paper to describe the phenomenon and the conditions of its occurrence and, at least tentatively, to discuss its nature and cause. Great numbers of phantoms may be found in 2: 1 brass, either hot-rolled or cold-rolled. They are also found in 70-30 brass, sometimes when hot-rolled and generally when cold-rolled. It is not believed that phantoms are confined to these alloys but this paper is limited to them for the purpose of description. HOT-ROLLED 2:I BRASS For illustration, therefore, a typical cake of hot-rolled 2: 1 brass has been chosen. This was rolled to a slab 7/8 in. thick, from a casting 5 in. thick by 24 in. wide by 18 in. high, which was believed to have been sound. After hot-rolling and cooling, the slab was sheared and a portion of such a shear cut is shown in Fig. 1. It would be difficult to convince anyone viewing this specimen that the metal was not unsound. The impression would be confirmed by the appearance of a tensile break, as shown in Fig. 2. This is an ordinary tensile-test piece from metal just described. Although there was nothing in its tensile strength or elongation that suggested unsoundness, it appeared run through with pipes and laminations. To question the reality of such a condition would imply questioning the obvious. But, considering the history of the metal, it w0uld be difficult to believe that it could be so bad as it appeared. It seemed reasonable, though, that if the defects were what they appeared to be, they could be traced back from the sheared or broken face.

Jan 1, 1945

By J. G. Eenink, R. A. Cunningham

One phase has been completed of a laboratory invesrigation of formations with relatively high permeability under conditions of overburden, formation and mud coltrmn pressures. The following statements are based on these tests within the limitations described. Drilling rate decreased when mud column pressure was greater than formation pressure. The decrease was primarily due to a layer of cuttings and mud particles held to the hole bottom by the difference in pressure. Much of the force of the bit was wasted in this layer and was unavailable for penetrating virgin formation. Adequate jet velocities helped clean the filter cake and chips away and resulted in increased drilling rate — the higher the jet velocity the faster the drilling rate. Drilling rate increased slightly when formation pres sure was greater than mud column pressure. The i11(reuse resulted from cleaning the hole bottom as formarion fluid flowed into the borehole. Overburden pressure had practically no effect on drilling rate. INTRODUCTION Some formations are difficult to drill in a wellbore hole but are easily drilled under atmospheric conditions in the laboratory. The reasons for this apparent difference in drillability are not fully understood. An increase in formation compressive strength causes a reduction in drilling rate. It has been shown by Griggs1, Handin2 and others3-1 that formation strength increases under conditions of high hydrostatic stress. Based on these results, a decrease in drilling rate would be expected with increased drilling fluid pressure in formations of low permeability having low formation fluid pressure. Such a decrease has been shown by Murray. et a1 and Eckel" This effect holds even when using nitrogcn under high pressure as the drilling fluid (unrc-ported tests from the Hughes laboratory). Poor bottom-hole cleaning may account for decreased drilling rates. Even though it may not be easily explained, evidence of poor cleaning can easily bc seen. One evidence is the increased drilling rate that accompanies decreased balling obtained with addition of oil in some muds used to drill shales.4,7,3 Many variables can affect drilling rates. These may include mud composition and properties, formation properties, bit types and operating conditions, formation fluid, mud column and overburden pressures. These must be studied a few at a time under carefully controlled conditions which simulate actual conditions as closely as possible. The purpose of this work was to investigate effect of overburden, formation and mud column pressures on drilling rates in permeable formations. These tests were suggested by conditions shown in Fig. I. Represented is a borehole drilled into a formation with relatively high permeability. In the vicinity of the hole bottom there exists a mud column pressure, P a formation fluid pressure, P and an overburden pressure, The mud has low water-loss properties and sufficient weight to more than overbalance the formation pressure. Laboratory investigation included a range with formation pressure greater than mud column pressure. NOMENCLATURE Pm mud column pressure = pressure of drilling fluid or mud at hole bottom Pf, formation pressure = pressure of fluid in intersticies of formation

By D. G. Swarthout, J. W. Savage, R. W. Guard

The Nb-N constitution diagvam has been examined from 1100° to 1450°C at 1 atm N2 pressure. On the basis of- our work plus that of Brauer and coworkers the stable nitvide Phases are: a) a solid solutlion, basic niobium (bcc) with nitrogen contained interstitially; NbN,, x = <0.40; b) ß NhNx,x = 0.39 to 0.45; hexagonal (W2C type) (NbzN); a =3.058A,c = 4.961 + 0.001A c) y NbNx x = 0.75 to 0.80; tetragonal (distorted NaCl type) (Nb4N3); a = 4.386A,c = 4.332 + 0.001A; d) 6 NbN,, x = 0.88 to 0.91; cubic (NaCl type); a = 4.3885 + 0.0007A; e) E NbNx x = 0.92 to 1.00; hexagonal (Tip type); a = 2.958A, c = 11.272 * 0.0015A. In addition, a metastuble transition phase 6&apos; has been observed and occurs only during the transition 6 — E. 6&apos; NbN has these distinguishing parameters: NbNx,x = 0.96; hexagonal (anti-NiAs type); a = 2.94A, c = 5 .46A. The high-temperature phase fields in the system are governed by two reactions: a) 6 + Y + E, a entectoid reaction occurring at 1270" ± 20° C; b) o + N2 = E, a 2 012 1 reaction occurring at 1370" ± 20° C. As part of a study of the electronic low-temperature. properties of transition metal nitrides, a number of specimens of niobium nitride were prepared. Preliminary observations on these specimens showed several points of disagreement with data already in the literature. It was, therefore, decided to determine the constitution diagram for the Nb-N system between 1100" and 1450°C. The objective of this research was to define the temperature and composition regions of stability of the various phases and to explain the differences among previously proposed diagrams. Review of Previous Literature. The research on the Nb-N system to 1964 has been summarized by storms.&apos; Although he does not present a phase diagram, his review covers the research on the system thoroughly. One of the earliest works on NbN is that of Ascher-mann and coworkers2 who studied the superconductivity of the cubic 6 NbN. Subsequent work by Horn and ziegler,3 Cook, Zemansky, and Boorse,1 Rögener:5 Schroder6 and sellmaier7 has qualitatively confirmed the first results on superconductivity, although their methods of preparation differed considerably. The constitution diagrams proposed for the system by Brauer and Esselborn8 and Elliott9 are shown in Fig. l(a)and (b). The diagram in l(a) has been modified by more recent results in Brauer&apos;s laboratory (private communication). Although 6&apos; is shown on this diagram, Brauer has indicated that he now believes 6&apos; to be a metastable phase in the temperature range shown. The diagram of Elliott, Fig. l(b), is based primarily on the results of Elliott and Komjathy10 on ni-trided niobium strip or rod specimens examined by X-ray diffraction and metallography. It will be noted that these proposed diagrams are in conflict with respect to the temperature and composition ranges of

Jan 1, 1968

By Nicholas J. Grant, David S. Bloom

An investigation of the Cr-Ni system has revealed that there exists a eutectoid transformation at about 1180°C. &apos;The transformation in chromium implied by the eutectoid reaction was detected at about 100°C below its melting point. Associated with the eutectoid transformation, a metastable transition structure has been found. THE Cr-Ni phase diagram is shown in current literature to be a simple eutectic system in which the high chromium end of the diagram is incompletely determined, Fig. 1. The last investigation of this system was undertaken in 1936.&apos; Because of limitations in metal purity, especially of chromium, and temperature measuring techniques, the diagram should be accepted with some reservations, as was indicated by Hansen.V or examwle.-, the wresence of the compound Cr²Ni, with a tetragonal structure," remains unverified and incompatible with the simple eutectic diagram. The work reported here began because of discrepancies that appeared in experimental studies in the binary alloys Cr-Ni and in the ternary system Cr-Mo-Ni. The existing binary Cr-Ni diagram failed to provide a complete explanation of observations made by microscope, X-ray, and thermal analyses. Experimental Methods The materials employed were of a higher degree of purity than were available to previous investigators. The Mond nickel used had a nominal purity of 99.87 pct, while the electrolytic chromium analyzed 99.03 pct with the major impurity being 0.5 to 0.7 pct oxygen with some iron. All alloys were melted in a vacuum furnace to remove dissolved gases, sufficient carbon was added to the charge to combine with all the oxygen as CO. Final analysis determined the carbon as about 0.02 pct and the oxygen around 0.06 pct or slightly more. Stabilized zirconia crucibles and thermocouple protection tips were used throughout and contributed no detectable impurity to the melts, as long as the oxygen in the chromium was kept low. Heats averaged about 250 g, which permitted about 2 in. of the thermocouple protection tips to be submerged. The temperature drop across the thermocouple protection tip was determined to be about 3°C, a minor source of error. The alloys, after removal from the vacuum furnace, were placed in a furnace operating in a purified argon atmosphere for the thermal analyses. An- nealed wolfram-molybdenum thermocouples provided the primary means of temperature determination, though a Pt-Pt-10 pct Rh couple was employed for a check when possible. A sensitive, high-speed Leeds and Northrup Speedomax recording potentiometer indicated the thermocouple output. X-ray diffraction patterns were obtained primarily on a Norelco unit, which permitted diffraction angles only up to 45" (28 = 90"). In general, either rotated or stationary solid samples were used, because it later evolved that many samples were susceptible to transformation resulting from the cold working involved in pulverizing. It was also noted that rotating a sample sometimes suppressed weak lines, so, usually, samples were not rotated. Later a high temperature camera was adapted for use at temperatures up to 1400 °C on the Norelco unit utilizing both solid and powdered samples. Unless otherwise noted, all X-ray patterns were made with a chromium tube and a vanadium filter. Further-

Jan 1, 1952

By Wendell S. Williams

Single crystals of TIC doped with boron at high temperat~ires develop second-phase inclusions. The inclusions are in the form of lamellae lying parallel to {l 11 } planes of the Tic matrix and can be vevealed by etching [100] cleavage faces of the boron-doped Tic crystals. measurements of the critical resolved shear stress. t, of TIC crystals containing such inclusions showed that the ropid drop in t wilh increasing temperatu.ve found for pure Tic was greatly reduced. At 1600°C, the inclusion containing crystals had a value of t five limes that of pure Tic. The hardening effect also was found to inhibit hot pressing of TiC powders containing boron impurity. Thermochemical and crys-tallographic arguments suggest that the inclusions are TiB2. The boron content of the hardened carbide is a few tenths of 1 pct. TITANIUM carbide is noted for its high room-temperature hardness. However, measurements of the critical resolved shear stress, T, of single crystals of Tic at high temperatures have shown that t decreases exponentially with increasing temperature.&apos; This temperature dependence of t is attributed to thermally activated dislocation mobility limited by a large Peierls stress.&apos; In turn, this large Peierls stress is believed to be a consequence of strong co-valent and ionic binding in Tic. The rapid drop in 7 with increasing temperature, characteristic of pure Tic, is lessened by the introduction of second-phase inclusions. Exposure of Tic to boron at high temperatures produces such inclusions. A report of the influence of boron on t in Tic is presented, followed by a discussion of the nature and formation of boron-containing inclusions in Tic which are believed to be responsible for the hardening effect. I) CRITICAL RESOLVED SHEAR STRESS OF BORON-DOPED Tic CRYSTALS Tic single crystal boules grown by Union Carbide Corp., Linde Division, were doped with boron by placing them in a carbon crucible packed with boron powder and heating in a vacuum furnace to 2000°C for 1 hr. Samples 1 by 1 by 3 mm were cleaved from these doped boules. High-temperature compression tests&apos; were made on these samples to determine the critical resolved shear stress as a function of temperature . The rapid drop in critical resolved shear stress found for pure Tic crystals&apos; did not occur: tests indicated that the boron-doped crystals at 1600°C had values of T equal to those of pure Tic crystals heated to only 1100°C, Fig. 1. No difference in the shape of the individual stress-strain curves was produced by the boron doping, but the stress scale was multiplied by a large factor. The hardening effect of boron in Tic probably extends to temperatures lower than those used in the present work (1100°C minimum). At room temperature, however, the influence of boron is difficult to determine because the stress required for gross plastic flow in pure Tic is SO high that in practice fracture cccurs first. Microhardness is the only test that can give an indication of the yield stress in Tic at room temperature. such measurements were made5 on boron-doped Tic; the matrix had a hardness value

Jan 1, 1967

By J. B. Newkirk

ABOUT twenty-seven years ago W. bergl discovered that interesting detail could be seen in an X-ray diffraction spot made with a rock-salt crystal if the recording photographic film were held very close to the reflecting crystal. He also showed that much of this detail could be explained in terms of the deformation structure of the specimen. In the same year, 1931, Fox and parr2 reported that X-ray reflections from a quartz crystal were much more intense while the crystal was undergoing piezoelectric oscillation than when it was at rest. This observation was soon confirmed (and explained in terms of X-ray extinction) by Barrett3 in the United States and by Nishikawa et a1.,4 in Japan. During the next few years Barrett refined Berg&apos;s method for making X-ray diffraction micrographs and applied it to the study of metallic crystals. He reported this work in the 1945 annual lecture of the AIME.5 Since 1945 relatively little use has been made of the Berg-Barrett (B-B) method for making diffraction micrographs, though considerable interest in investigating subcrystal structures by other methods has developed. Some of these methods depend upon evaporation6 or chemical etching7 and, therefore, suffer from the occasional intrusion of subtle artifacts such as those recently reported by Hooker for leada and Welsh for aluminum.9 Other methods require the introduction of foreign elements which "decorate" the substructure in some way, thereby rendering it detectable by direct" or indirect1&apos;. visual examination. Still others depend upon complex and often highly questionable analyses of X-ray diffraction line profiles. There have also been a number of related X-ray techniques, such as the Lambot,12 Schulz13 and Merlini and Guinier,14 which have proved to be quite useful for specific applications. Some of these methods give a picture of the substructure which is more or less directly related to the shape and the topography of the specimen. The Berg-Barrett method carries this desirable feature to the limit. Closely related to the B-B method are three photographic X-ray techniques recently described by Lang.15 These methods give beautiful pictures of the internal structure of crystals but are limited by the facts that the required apparatus is rather complex, exposure times are long, and the specimen crystals must be thin. An experimental appraisal which I have recently made of the original B-B method has shown that this simple technique is not only inexpensive and convenient, but can give more information than was apparently realized by its inventors. For example, first-order subgrains in iron-silicon crystals were clearly delineated and their relative orientation subject to description. Also defect structures could be seen within the subgrains and in some materials slip bands could be clearly seen with respect to the topography of the rest of the specimen. This much had already been described by Barrett. However, in the present study it was found that the actual sites of individual dislocations which emerge upon the crystal surface could be located. Furthermore, by a simple procedure, the direction (but not sign) of the dislocation Burgers&apos; vector could be defined as well.

Jan 1, 1960

By P. F. Gnirk, J. B. Cheatham

An experimental investigation has been made to study the effects of tooth angle and confining pressure on the force required for indentation of dry rock samples under confining pressure. In these experiments static single-tooth indentations were made on two standstones, a limestone, a schist and a slate under confining pressures of 5,000 to 15,000 psi. Sharp wedge-shaped teeth with included angles ranging from 30°to 105°were used. In all cases the force-displarenzent curves are approxinlately linear for rocks tested under confining pressure, as contrmted with the discontinuous curves obtained for silnilar rocks at atmospheric conditions. Photonzicrographs of thin sections through the craters indicate very little evidence of chip formation during indentation. In general the experimental data lie between calculated values for perfectly rough and perfectly smooth tooth-rock interfaces. INTRODUCTION The variables associated with ctrilling at depth are numerous and, in many instances, are not easity isolated and controlled. Also, many of these variables are interdependent; however, if the variables which are sufficiently independent of each other are held constant and are appropriately introduced, the dependent variables can be more easily studied and evaluated. It is the purpose of the present investigation to study experimentally the simplest case of bit tooth-rock interaction. In essence, the experiments have involved the static loading of sharp wedge-shaped tools on the surfaces of effectively semi-infinite dry rock samples subjected to confining pressures. During this investigation the following quantities have been maintained constant: 1. Pore pressure: atmospheric (i.e., the rock is dry). 2. permeability: although the rocks may be permeable, they are "jacketed" in such a manner that the fluid is not permitted to flow through them. 3. Temperature: 75F. 4. Rate of loading: essentially static (approximately 0.002 in./second). 5. Bit tooth: a sharp wedge-shaped tooth loaded normal to the rock surface. 6. Rock surface: smooth and flat. 7. Drilling fluid: hydraulic oil. In addition to the above conditions, the rock surface was free of a layer of cuttings. There was no indexing to previously indented surfaces, and the influence of corners of the borehole was neglected because the rock samples were effectively semi-infinite. The following quantities have been varied, and the resulting effects have been studied: 1. Rock a) Type (e.g., limestone, sandstone, etc.). b) Mechanical properties ) Necessarily dependent c) Porosity on type of rock. 2. Bit tooth (included angle of wedge-shaped tooth). 3. Depth of penetration. 4. cobfining pressure. On the basis of laboratory experiments which have shown that many rocks exhibit ductile behavior at confining pressures corresponding to depths usually reached during drilling,&apos;.&apos; a theory has previously been advanced which predicts the force required for penetration by a single sharp wedge tooth into a ductile* material.&apos; The material is assumed to be isotropic, homogeneous and rigidly plastic (no elastic deformation) and to obey the Coubomb yield criterion (Figs. 1 and 2). Equations governing the force required for penelration are given for two extreme cases:** 1. A smooth, perfectly lubricated tooth-rock interface (fridionless boundary), in which the solution gives a minimum value for the penetrating force: in which F = force of the tooth, b = length of tooth edge,

By Lawrence B. Wright

The Republic district, Washington, is of new interest because of the discovery of new gold-silver ore within a unique structural pattern. The camp was revived in 1937 fol1owing installation of a plant to treat low-grade disseminated ore at Knob Hill and further stimulation followed discovery of "cross vein" breccia ores in 1939. Previous writers 1-2 ascribed the quartz veins to a latite porphyry stock, but are in disagreement as to its precise location and extent. This study leads to the conclusion that the ores have a more profound parentage linked to a broad system of thrust faults and folds, the mechanical origin of which is related to a southward trending (Sanpoil) syncline connecting with the Lewis and Clark zone of shift described by Billingsley and Locke3 in 1939. The Republic anticliue and a cross anticline recumbent against Cretaceous granodiorite. and involving some 4000 ft of Eocene andesite flows and early Miocene lake beds, localize the ores, mainly along the east flank, in a series of openings simulating drag folds and steeper than the folded flows. These broad structural features no doubt reach deeply into the basement rocks, where at appropriate crossings and junctions it is suggested that heat effects gave rise to ore-making materials, including, in this instance, intrusive breccias that later were mineralized, and comprising the broader bodies of new ores. The breccia ore is seen crosscutting the earlier narrow quartz veins with a welding of the two at junction areas by a second surge of ore minerals. The ore mined and developed since 1937 equals district production from 1896 to 1937 The ores are typified by cherty quartz, adularia and some barite, with fine pyrite and marcasite, polybasite, pyrargyrite, tetrahedrite and gold. Selenium is present, possibly with gold, as a normal selenide. The disseminated ores, as well as the vein and breccia ores, are localized principally in one 500-ft flow (Knob Hill andesite), which has been traced around the crest of the low northward-plunging Republic anticline. The gold-silver ratio in the earlier narrow veins is about I to 4 and in the disseminated and breccia ores, I to 7. The latter higher silver ratio is deemed to reflect the character of the second surge of mineralization. Sills and dikes of the Columbia River (Miocene) basalt cut the folded structure and ore, thus placing the mineralization in the middle Miocene. Introduction The Republic district of north central Washington is of new interest because of the discovery, development and extraction of new gold-silver ore; also, because of a unique local structural pattern believed to be integral with the broader tectonic mechanism of the continental framework. This district had 40 years of modest rating following its discovery in 1896. Its narrow ore bodies, complex mineralogy. and early inadequate metallurgy, together with the apparent bottoming of ore near 1000 ft, limited production to 300,000 oz of gold and 1,000,000 oz silver between 1897 and 1914. The camp was then reduced to lease Life until 1937, when the gold price increase of 1933 to $35 per ounce

Jan 1, 1949

By Lawrence B. Wright

The Republic district, Washington, is of new interest because of the discovery of new gold-silver ore within a unique structural pattern. The camp was revived in 1937 fol1owing installation of a plant to treat low-grade disseminated ore at Knob Hill and further stimulation followed discovery of "cross vein" breccia ores in 1939. Previous writers 1-2 ascribed the quartz veins to a latite porphyry stock, but are in disagreement as to its precise location and extent. This study leads to the conclusion that the ores have a more profound parentage linked to a broad system of thrust faults and folds, the mechanical origin of which is related to a southward trending (Sanpoil) syncline connecting with the Lewis and Clark zone of shift described by Billingsley and Locke3 in 1939. The Republic anticliue and a cross anticline recumbent against Cretaceous granodiorite. and involving some 4000 ft of Eocene andesite flows and early Miocene lake beds, localize the ores, mainly along the east flank, in a series of openings simulating drag folds and steeper than the folded flows. These broad structural features no doubt reach deeply into the basement rocks, where at appropriate crossings and junctions it is suggested that heat effects gave rise to ore-making materials, including, in this instance, intrusive breccias that later were mineralized, and comprising the broader bodies of new ores. The breccia ore is seen crosscutting the earlier narrow quartz veins with a welding of the two at junction areas by a second surge of ore minerals. The ore mined and developed since 1937 equals district production from 1896 to 1937 The ores are typified by cherty quartz, adularia and some barite, with fine pyrite and marcasite, polybasite, pyrargyrite, tetrahedrite and gold. Selenium is present, possibly with gold, as a normal selenide. The disseminated ores, as well as the vein and breccia ores, are localized principally in one 500-ft flow (Knob Hill andesite), which has been traced around the crest of the low northward-plunging Republic anticline. The gold-silver ratio in the earlier narrow veins is about I to 4 and in the disseminated and breccia ores, I to 7. The latter higher silver ratio is deemed to reflect the character of the second surge of mineralization. Sills and dikes of the Columbia River (Miocene) basalt cut the folded structure and ore, thus placing the mineralization in the middle Miocene. Introduction The Republic district of north central Washington is of new interest because of the discovery, development and extraction of new gold-silver ore; also, because of a unique local structural pattern believed to be integral with the broader tectonic mechanism of the continental framework. This district had 40 years of modest rating following its discovery in 1896. Its narrow ore bodies, complex mineralogy. and early inadequate metallurgy, together with the apparent bottoming of ore near 1000 ft, limited production to 300,000 oz of gold and 1,000,000 oz silver between 1897 and 1914. The camp was then reduced to lease Life until 1937, when the gold price increase of 1933 to $35 per ounce

Jan 1, 1949

By G. W. Healy, W. D. Forgeng, N. R. Griffing

The liquidus surface of the C-Cr-Fe system to 1900°C has been mapped from carbon solubility and freezing point measurements, metallographic observations, and published data. In the graphite field, the surface drops precipitously to meet a slope descending from the Cr3C2-C join through the mixed carbide fields to a meandering eutectic valley; this flows from the Cr-C to the Fe-C edge. On the low-cavbon side of the valley, the surface rises to the chromium corner. 1 HE purpose of this inquiry was to gain a more complete knowledge of the C-Cr-Fe liquidus surface. This required an extensive study of carbon and chromium-rich alloys which, in the past, have received the least attention. Sanbongi el al.1 measured the solubility of carbon in liquid alloys containing up to 25 wt pct Cr at temperatures of 1460" and 1545°C and found that it increased with chromium content and temperature. Lucas and wentrup2 also made solubility experiments in graphite crucibles, but at higher chromium contents in the range of 38 to 80 pct and at temperatures of 1550" to 1700°C; however, their experiments were relatively few, and the effect of temperature was not consistent. The present investigation included compsitions ranging from 0 to 94 pct Cr and 1.4 to 11.7 pct C at temperatures up to 1800°C. Saturation experiments in graphite crucibles, thermal analyses during freezing, and metallographic and X-ray diffraction studies were employed to obtain desired information which, together with published data from other investigations about the binary edges and the ternary system at lower carbon levels, made possible the construction of a comprehensive C-Cr-Fe liquidus surface. C-CR-FE LIQUIDUS SURFACE The derived ternary liquidus surface is shown in Fig. 1 where the solid curves are liquidus isotherms. The dashed curves and the binary edges are the liquidus field boundaries of the primary crystals, the arrows along these boundaries indicating their direction with decreasing temperature. Each intersection of three internal boundaries is the composition of liquid involved in four-phase isothermal equilibrium with the three primary crystals whose liquidus fields touch there. It may be observed that a total of six four-phase equilibria occur at melt temperatures. The general topography of the liquidus surface consists of a eutectic valley sloping down from the Cr-C edge at 3.2 pct C to the Fe-C edge at 4.25 pct C. The liquidus surface rises in two directions from the valley, one hillside terminating at the Cr-Fe edge while the opposing hillside rises toward the carbon corner out beyond the top edge of Fig. 1. Both hillsides are interrupted by intersections of surfaces or joints representing the liquid colmpositions of various three-phase equilibria. Seven primary crystals occur, namely a(bcc), ?(fcc), graphite, (Fe, Cr)3C capable of dissolving as much as 15 pct Cr, and three different chromium carbides in which iron is partially soluble by substitution for chromium. The composition ranges of the primary l~hases at melt temperatures are shown

Jan 1, 1962

By H. G. Landua, Leah L. Naugle, H. H. Lowry

Evidence has been accumulating in recent years, in part from the work of the Coal Research Laboratory, that coals belong to a family of natural polymers and that even in complex reactions the differences between coals are quantitative and not qualitative. This point of view leads to the expectation that if a series of coals were subjected to a closely controlled set of experimental conditions the results obtained should be related to the chemical analyses of the individual coals. The data accumulated over the past 10 years by the Bureau of Mines in its (&apos;Survey of Coke-, Gas-, and By-Product-Making Properties of American Coals," in what has come to be recognized as the Bureau of Mines-American Gas Association (BM-AGA) carbonization assay test,l-l2 offer an unusual opportunity to check this conclusion. The present paper reports an analysis of the data on the first go coals and coal blends— including coals numbered I to 55B, inclusive —which have been carbonized according to a standard procedure at intervals of 100°C. from 500° to 1100° in either or both 13 or 18-in. cylindrical retorts.13 In Table I are given the name of the seam from which the sample was obtained, the analytical data used, and the reference to the original publication of the Bureau of Mines. The coals range in fixed carbon from 46.2 to 79.0 per cent, in volatile matter from 15.4 to 41.3 per cent, in ash from 2.1 to 15.9 per cent, in moisture from 0.8 to 19.7 per cent, and in total sulphur from 0.40 to 4.44 per cent; therefore the entire gamut of bituminous coals is represented. The petrographic nature of the individual coals is not considered in the following analysis, although both "normal" bright coals and splint coals are included in the samples studied. For information on the petrography of the coals and for further information characterizing the coals the original papers should be consulted. Although the coals that are included extend over the whole range of bituminous coals, they do not cover this range entirely adequately. In particular, only 13 of the 90 coals have moisture contents greater than 3 per cent. This concentration at low moisture values means that the effect of moisture, which is an important factor, cannot be determined with as much certainty as would be desirable. All the coals were not tested at every temperature and in both retort sizes. Only the first 30 coals were tested at 1100°, and only about 50 at the other temperatures, except at 900°, where nearly all of them were included. In the accompanying tables the actual number of observations entering into each correlation is given. In this study equations are given for calculating analyses, yields, and properties of coke and by-products from the coal analyses. To decide whether these equations are satisfactory it is necessary to know the accuracy with which these quantities were measured in the assay tests.

Jan 1, 1942

By Leah L. Naugle, H. H. Lowry, H. G. Landua

Evidence has been accumulating in recent years, in part from the work of the Coal Research Laboratory, that coals belong to a family of natural polymers and that even in complex reactions the differences between coals are quantitative and not qualitative. This point of view leads to the expectation that if a series of coals were subjected to a closely controlled set of experimental conditions the results obtained should be related to the chemical analyses of the individual coals. The data accumulated over the past 10 years by the Bureau of Mines in its (&apos;Survey of Coke-, Gas-, and By-Product-Making Properties of American Coals," in what has come to be recognized as the Bureau of Mines-American Gas Association (BM-AGA) carbonization assay test,l-l2 offer an unusual opportunity to check this conclusion. The present paper reports an analysis of the data on the first go coals and coal blends— including coals numbered I to 55B, inclusive —which have been carbonized according to a standard procedure at intervals of 100°C. from 500° to 1100° in either or both 13 or 18-in. cylindrical retorts.13 In Table I are given the name of the seam from which the sample was obtained, the analytical data used, and the reference to the original publication of the Bureau of Mines. The coals range in fixed carbon from 46.2 to 79.0 per cent, in volatile matter from 15.4 to 41.3 per cent, in ash from 2.1 to 15.9 per cent, in moisture from 0.8 to 19.7 per cent, and in total sulphur from 0.40 to 4.44 per cent; therefore the entire gamut of bituminous coals is represented. The petrographic nature of the individual coals is not considered in the following analysis, although both "normal" bright coals and splint coals are included in the samples studied. For information on the petrography of the coals and for further information characterizing the coals the original papers should be consulted. Although the coals that are included extend over the whole range of bituminous coals, they do not cover this range entirely adequately. In particular, only 13 of the 90 coals have moisture contents greater than 3 per cent. This concentration at low moisture values means that the effect of moisture, which is an important factor, cannot be determined with as much certainty as would be desirable. All the coals were not tested at every temperature and in both retort sizes. Only the first 30 coals were tested at 1100°, and only about 50 at the other temperatures, except at 900°, where nearly all of them were included. In the accompanying tables the actual number of observations entering into each correlation is given. In this study equations are given for calculating analyses, yields, and properties of coke and by-products from the coal analyses. To decide whether these equations are satisfactory it is necessary to know the accuracy with which these quantities were measured in the assay tests.

Jan 1, 1942

By R. I. Jaffee, J. G. Dunleavy, W. Hodge, H. R. Ogden

IN a search for an improved conductor for use in field wire for the L. S. Army Signal Corps, an alloy of copper and silver was developed from which it was possible to obtain 29 B & S ga. strands with tensile strengths in excess of 160,000 psi combined with an electrical conductivity of over 70 pct IACS. Such a favorable combination of strength and electrical conductivity has not been reported previously in the rather extensive literature covering this subject. The properties obtained from various binary alloys of copper and silver, together with the method of fabrication of these alloys which has been developed to obtain the properties desired in fine wire strands, are discussed in this paper. LITERATURE The effect on the electrical conductivity of copper of the various elements in solid solution is shown in Fig I, taken from published data by J. O. Linde and others.&apos; It will be noted that silver in solid solution depresses the electrical conductivity to a lesser extent than any other element for which data are given, and is followed rather closely by cadmium, and then by chromium. Zinc, which lies between cadmium and chromium, has so high a solid solubility in copper that the data for zinc are scarcely comparable to the data for the other two in the range covered. Not many data are available on the strain hardening of copper-rich Cu-Ag alloys. Corson2 reports a 3 pct Ag alloy properly cold worked and annealed to have 100,000 psi tensile strength and 90 pct IACS conductivity. On straight cold working, Hessenbruch3 reports 101.000 psi for a 5 pct Ag, 0.3 pct Be alloy, and 129,000 psi for a 30 pct Ag, 0.5 pct Be alloy. Here it would he expected that much of the strain hardening came from the silver content of the alloys. The copper-rich side of the Cu-Ag diagram, according to Stockdale,4 is shown in the upper part of Fig 2. The electrical conductivities for copper-silver alloys annealed at 750 and 350°C, taken from the work of Johansson and Linde,5 are shown in the lower part of Fig 2. The sloping line corresponds to the conductivity of solid solutions of silver in copper, and the horizontal offshoots correspond to the conductivity of the two-phase alloys in equilibrium at the two temperatures shown. The electrical conductivities are very high, even for the 750°C anneal. The potentiality for age hardening from supersaturated alpha copper solutions appears to be excellent from the solubility line, but Smith and Lindlief6 have shown that the response to age hardening of solution-annealed alpha alloys is not good. They found that the tensile strength of a 5 pct Ag alloy aged at various temperatures was not as great as in the quenched condition, even though, anomalously, the hardness increased from RB68 to RB78 by annealing for 4 hr at 400°C after a 750°C quench. Weist7 also found that the alloys increased in hardness

Jan 1, 1948

By K. D. Hester, A. W. Fletcher

A nickel-copper sulphide concentrate was treated in a pilot plant at Warren Spring Laboratory during 1961, by a hydrometallurgical roast-leach-solvent extraction process devised to cleanly separate the metal values and produce acid sulphate liquors containing the metals. It is shown that 86 pct of the nickel and 95 pct of the copper could be leached from the calcine, after a sulphatizing roast on finely ground flotation concentrate. Iron was removed from the leach liquor by limestone neutralization with a small loss of values. Copper and nickel were separated by solvent extraction with naphthenic acid in kerosene after partial neutralization of the iron-free liquors with ammonium hydroxide. Hydrogen sulphide and chlorine were used to remove zinc (and residual copper) and cobalt impurities respectively. The recovery of pure copper and pure nickel, by electrowinning, from the acidic solvent extract strip liquors finally produced, appears technically feasible. An economic analysis of production costs shows that small, geographically isolated, nickel-copper sulphide deposits cannot usually be worked profitably by established processes. The requirements for profitable operation on a comparatively small scale could possibly be met by a flotation-roast-leach process. Two difficulties, obtaining satisfactory extraction of nickel from a sulphide concentrate and separating the copper and nickel in solution, have prevented the previous use of this method. A solution to the first problem, dissolution of the nickel, was described in a recent paper by Thornhill.1 It was shown in this paper that copper and nickel in a flotation concentrate could be oxidized to water soluble sulphates by roasting in a fluidized bed with added salt cake. Workers at the Warren Spring Laboratory have shown that the separation of copper and nickel can be accomplished by solvent extraction using a relatively inexpensive carboxylic acid, naphthenic acid. Moreover, the mineral acid required to strip values from the loaded solvent could be produced, and the metals recovered, by electrowinning; thus the latter section of the process was regenerative. The removal of iron from the leach liquor and the elimination of impurities such as zinc and cobalt before nickel electrowinning would be necessary to complete the flowsheet. The process under investigation could therefore be summarized (Fig. 1) as follows: 1) Flotation to produce a bulk sulphide concentrate. 2) Fluidized bed roasting to sulphate the nickel and copper minerals. 3) Leaching of roaster calcine to extract soluble nickel and copper. 4) Precipitation of iron from the separated leach liquor by air oxidation after the adjustment of pH and temperature. 5) Recovery of copper from the iron-free Liquor by pH adjustment and liquid-liquid extraction. 6) Purification of the copper raffinate by removing zinc and residual copper as insoluble sulphides and cobalt as cobaltic hydroxide. 7) Recovery of nickel from the purified liquor by pH adjustment and liquid-liquid extraction. Laboratory and pilot plant studies detailed below, were carried out at the Warren Spring Laboratory, to test the feasibility of each one of the unit processes and to obtain preliminary plant design data. FLOTATION The ore was an altered basic rock containing concentrations of magmatic sulphides.

Jan 1, 1964

By M. S. Burton, J. E. Ritter

The sessile-drop technique was employed to study the effect of atmosphere and alloy additions of titanium and chromium on the surface tension and contact angle of nickel on sapphire substrates at 1500oC. Shear tests were conducted on the solidified sessile drops. The liquid-gas surface tension of pure nickel on sapphire was found to be 1747 ergs per sq cm, with a contact angle of 109.6 deg. The surface tension and contact angle were not affected significantly by the four atmospheres, vacuum, impure argon, pure argon, and pure hydrogen. Small additions of titanium and chromium decreased the contact angle and for the same alloy content, contact angles were lower in pure argon than in pure hydrogen. On the basis of shear-test results , the most probable cause for adhesion in the Ni-Al2O system is the formation of NiO:Al2O3 spinel at the interface; in the titanium alloy-Al2O3 system adhesion is thought to be due to a mechanical interlocking effect; in the chromium alloy-Al2O3 system adhesion is believed to be the result of solid-solution formation involving Cr2O3 and Al2O3 at the interface. In the last few years there has been considerable interest in reinforcing metals with ceramic whiskers. It has been postulated that, by reinforcing nickel with sapphire whiskers, high-temperature strengths su- perior to those of the best current nickel alloys can be achieved.&apos; To fabricate a whisker-metal composite having optimum density and strength, understanding of wettability and adherence in the system is of prime importance. Although there has been some previous research in this a a need for further studies has been cited4-8 to understand better the effects of impurities, alloys additions, and atmosphere on the wetting and bonding of metals to metal oxides. The purpose of this research was to investigate the factors involved in the wetting and adherence of nickel/nickel alloys to sapphire (single-crystal a Al2O3). Sessile-drop experiments were conducted in vacuum, impure argon, pure argon, and pure hydrogen, to determine the effect of atmosphere on the contact angle of the metals on sapphire, and the liquid-gas surface tension of pure nickel. The solidified sessile drops were sheared from the sapphire substrate to measure the bond strength between the metal and ceramic. The alloy additions chosen were titanium and chromium since both enhance the wetting of nickel on sapphire.2, 3c Also, titanium is commonly used when brazing metal-to-ceramic seals to improve adherence. Since chromium forms an oxide that is completely soluble in sapphire, it was thought that the oxide could serve as a transition phase to promote bonding between the Ni-Cr alloy and sapphire. I) EXPERIMENTAL APPARATUS AND PROCEDURE The sessile-drop apparatus was a horizontal furnace, with an induction-heated, cylindrical molybdenum susceptor in a water-cooled Pyrex chamber. This apparatus was patterned after that of Williams and Nielsen.7 A flat Pyrex window at each end of the furnace allowed temperature measurements to be made at one

Jan 1, 1968

By K. A. Semlak, F. N. Rhines

NFILTRATION is a term used to designate that i- process by which the pores of a metal powder are filled with a relatively low-melting liquid metal through the action of capillary forces. This is accomplished in practice either by heating the porous body in contact with the solid infiltrant metal above the melting point of the latter, or by preheating the porous body separately and then dipping it into the liquid metal. The liquid, as it sweeps through the porous body, replaces the gases progressively, thus yielding a relatively dense product in a short time.&apos; Liquid-phase sintering, which is related to infiltration, is a process by which a mixture of two or more metal powders is sintered at a temperature between the liquidus and solidus of the ultimate alloy.&apos; According to Cannon" liquid-phase sintering can be divided into three stages which he calls liquid flow, accommodation, and solid sintering. The largest density increase occurs during the first stage, where the lower melting component melts and, driven by capillary forces, flows among the particles of the higher melting component, where, after dissolution of the bonds between the solid particles, it moves them into close packing. This happens so quickly that little has yet been learned of its mechanism. A study of the rate of capillary rise of a liquid metal in a higher melting metal-powder compact may be expected, therefore, to contribute not only to a firmer understanding of the process of infiltration as such but also to a more extensive knowledge of what occurs during the initial stage of liquid-phase sintering. Theoretical Basis In order to derive a mathematical expression of the rate of infiltration, it has been assumed that a powder compact consists of a great many parallel capillary tubes and that the rate of rise of a liquid in an average capillary channel represents the rise in the entire compact. For a straight capillary, assuming that Poiseuille&apos;s law obtains for the non-stationary state and that wetting is very rapid, Ligenza and Bernstein&apos; have derived the following differential eauation of motion where h is the height of rise of the column of liquid at time t, R, is the radius and 1 the length of the capillary, t) and 7, the viscosities of liquid and air, respectively, p and p, the density of the liquid and air, respectively, y the liquid-gas surface tension, 0 the liquid-solid contact angle, and g the acceleration due to gravity. The term on the left of Equation [I] represents the rate of change of momentum of the contents of the capillary tube. On the right the terms represent, respectively, the forces due to a) surface tension, b) viscous resistance, c) gravity, and d) end-drag effect. Equation [I] is not amenable to explicit solution, but for a tube of sufficiently small radius, the rate of rise may be slow enough so that the rate of change of momentum and end-drag terms may be neglected. The validity of this simplification was established by Ligenza and Bernstein&apos; by graphical differentiation of observed data obtained from organic liquids rising in glass tubes. The solution of this simplified case is:

Jan 1, 1959

By C. W. Allen, B. D. Cullity, H. S. Choi

The torsional deformation of aluminum and magnesium crystals is investigated, with particular reference to the dependence of proportional limit on crystal orientation. The proportional limit is found to be governed by the average value of the resolved shear stress on the most highly stressed slip systems, but the proportional limit does not strictly obey a critical-resolved-shear-stress law. The behavior of a cylindrical single crystal stressed in tension is well known: plastic flow begins when the resolved shear stress on the most highly stressed slip system reaches a critical value. There is much less understanding of the effect of torsion on such a crystal and on the way in which the critical-resolved-shear-stress law should be applied to torsional deformation. In the present paper particular attention is paid to the dependence of plastic yielding on crystal orientation and lesser attention to the mechanism of flow after yielding has occurred. New work on aluminum and magnesium crystals is presented, and previous results obtained in this laboratory on magnesium1 are re-examined. STRESS DISTRIBUTION The problems involved in torsional deformation of single crystals are due entirely to the complexity of the stress distribution. In tension, if loading conditions are perfect, the shear stress on any particular slip plane is completely uniform over the entire area of that plane. In torsion, on the other hand, the stress on any selected plane in a particular direction varies not only from center to edge of the specimen but also around its perimeter. It is convenient to express the stress at any point in terms of t0, which is the shear stress acting at the surface of a cylindrical specimen on a plane normal to the axis and in a direction tangential to the cylinder. At point P of Fig. 1 this stress acts in the direction of axis 2 and is given by To = 2T/pr3 [1] where T is the applied torque and r the specimen radius. This stress can be resolved on any chosen slip system, and details are given in the Appendix. Let P be the point on the specimen surface where the stress is to be evaluated; P is defined by its angular distance A from an arbitrary reference line through 0 normal to the axis. his line is usually taken as the direction of incidence of the X-ray beam used to determine the crystal orientation.) Then the shear stress t, acting at P in direction Dona plane whose normal is N is given by Ts/TO = sin ? 0, cos ?d sin (?0, - ?) + cos ?, sin ?d sin (?d - ?) [2] where 0, and Od are the angles between N and D, respectively, and the axis, ?0 and ?d are the angles between the projections of N and D, respectively, on the transverse plane and the reference line through 0. By means of Eq. [2], the stress 7, acting in any given slip direction can be computed. In the previous work on magnesium1 only gross slip tangential to the specimen surface was considered, and this

Jan 1, 1963

By Leah L. Naugle, H. G. Landau, H. H. Lowry

EVIDENCE has been accumulating in recent years, in part from the work of the Coal Research Laboratory, that coals belong to a family of natural polymers and that even in complex reactions the differences between coals are quantitative and not qualitative. This point of view leads to the expectation that if a series of coals were subjected to a closely controlled set of experimental conditions the results obtained should be related to the chemical analyses of the individual coals. The data accumulated over the past 10 years by the Bureau of Mines in its "Survey of Coke-, Gas-, and By-Product-Making Properties of American Coals," in what has come to be recognized as the Bureau of Mines-American Gas Association (BM-AGA) carbonization assay test,1-12 offer an unusual opportunity to check this conclusion. The present paper reports an analysis of the data on the first go coals and coal blends-including coals numbered I to 55b, inclusive -which have been carbonized according to a standard procedure at intervals of 100°C. from 500° to 1100° in either or both 13 or I8-in. cylindrical retorts." In Table I are given the name of the seam from which the sample was obtained, the analytical data used, and the reference to the original publication of the Bureau of Mines. The coals range in fixed carbon from 46.2 to 79.0 per cent, in volatile matter from 15.4 to 41.3 per cent, in ash; from 2.1 to 15.9 per cent, in moisture from o.8 to 19.7 per cent, and in total sulphur from 0.40 to 4.44 per cent; therefore the entire gamut of bituminous coals is represented. The petrographic nature of the individual coals is not considered in the following analysis, although both "normal" bright coals and splint coals are included in the samples studied. For information on the petrography of the coals and for further information characterizing the coals the original papers should be consulted. Although the coals that are included extend over the whole range of bituminous coals, they do not cover this range entirely adequately. In particular, only 13 of the go coals have moisture contents greater than 3 per cent. This concentration at low moisture values means that the effect of moisture, which is an important factor, cannot be determined with as much certainty as would be desirable. All the coals were not tested at every temperature and in both retort sizes. Only the first 30 coals were tested at 1100°, and only about 50 at the other temperatures, except at 900°, where nearly all of them were included. In the accompanying tables the actual number of observations entering into each correlation is given. In this study equations are given for calculating analyses, yields, and properties of coke and by-products from the coal analyses. To decide whether these equations are satisfactory it is necessary to know the accuracy with which these quantities were measured in the assay tests.

Jan 1, 1941

By D. H. Gieskieng

Published tables of jaw crusher capacities are compiled for the most part from field performance data, interspersed with interpolations, extrapolations, various safety factors, and other modifications. Such a table attempts to balance and equalize field data from widely Werent materials, with differences of crushability, efficiency of feeding, sizing of the feed, and so on. The tests described in this paper were undertaken with the objectives of checking previously reported capacities; of studying the effects of various factors upon the capacity, including jaw plate curvature; and, if possible, of deriving a general capacity equation. Such an equation has been derived from the data obtained in these tests. It is given together with factors for its use. While more accuracy than is usually required may be obtained by careful application of the equation, it is of simple form and provides a convenient reference plane upon which the potential capacity of various crushers may be compared, and with which operating adjustments may be made on existing installations. The principal deviation in these tests from the usual approach consists of a laboratory technique which has been developed for the production of selected capacity data. Recording instruments are connected to crushers in such a manner that a continuous record is produced which discloses the inherent maximum capacity of the crusher and shows capacity decreases caused by hangups. The capacity effects of various crushing conditions are made more evident by this arrangement. The recording instruments were first applied to a standard sized 10 by 7 in. Blake-type jaw crusher in the laboratory. Suficient tests were run on this with various combinations of setting, throw, speed, feed sizing, shapes of jaw plates, and other operating features, to establish the individual effect of each on the capacity. The instruments later were applied to much larger crushers in the field, through the excellent cooperation of the managements in the Mesabi Iron Range, and data were obtained which closely corroborated the established trends. The capacity equation resulting from the test work is made up of a series of factors, each representing the contributing effects of setting, speed, width of chamber, nip angle, feed density, type of jaw plates, stroke, and the overall operating technique. Fortunately, most of these factors were revealed to be in direct proportion to the capacity for straight plate chambers. This equation is also applicable to chambers using curved plates, with slight modifications resulting from the capacity limitation of the upper portion of the crushing chamber. The equation has been derived from tests covering a very wide range of feed density and hardness. It has been found valid, providing that the feed material is either nonpacking in character, as is usual, or allowance in designing the crushing chamber shape has been made to accommodate this characteristic. Preliminary investigation has shown that the equation is also applicable to single-toggle jaw crushers. Conditions of this are that the top of the flywheel rotate towards the top of the crusher opening, and that the horizontal motion of the swing jaw relative to the stationary jaw at the discharge opening be considered as the stroke. The relatively large upper chamber jaw motion would probably result in realiza-

Jan 1, 1950

By J. T. McGrath, G. B. Craig

Tensile tests on aluminum single crystals, grown from the melt, revealed that the yield stress of these crystals was raised as the amount of striation substructure was increased. The number of striation-type boundaries was varied by changing the rate of growth of the crystals. The results are interpreted in terns of a blockage of dislocation movement by striation boundaries. IMPERFECTIONS are known to have a large effect on the mechanical properties of metals. Teghtsoonian and Chalmers 1 studied a block or striation-type substructure in tin and found that the formation of the striations depended upon rate of crystal growth and orientation. They found that the angular misorienta-tion between neighboring striations varied between 15 min and 5 deg. Atwater and chalmers2 investigated striations in tin and lead, and found that purity was another factor which influenced their formation. There was a limiting purity above which the striations were straight and regular. There is little information in the literature concerning how substructures in melt-grown crystals affect strength. washburn3 introduced small-angle boundaries into zinc by a shear process and found a subsequent increase in yield stress which he attributed to the presence of these boundaries. Lauriente and pond4 found the critical resolved shear stress in aluminium crystals grown from the melt, to increase with etch pit density. The etch pits were used as an indication of growth imperfections. In Hibbard&apos;s5 work on lineage structure in copper crystals grown from the melt, he tested one crystal containing interlineage boundaries, and found a 50 pct increase in the critical resolved shear stress. Fleischer and Chalmers6, in a recent paper, mention briefly that, in the production of aluminium crystals from the melt when the growth rate was raised from 1.2 to 18 cm per hr, the yield stress increased 50 pct. They felt that the increase in yield stress with rate of growth might be attributed to a higher concentration of impurities in the gage length and also might be affected by the increased number of small-angle boundaries (striations). The present investigation was undertaken to determine the effect of the striation substructure on the strength of aluminum single crystals. EXPERIMENTAL PROCEDURE Aluminum single crystals of 99.9992 purity were grown from the melt using a technique described by Chalmers.7 The growth rate was varied from 0.6 to 20 mm per min, thus producing crystals with varying numbers of striation boundaries. To avoid prior deformation, the crystals were chemically cut to the desired length with a saturated solution of cupric chloride. They were then annealed at 580°C for 24 hr and allowed to cool slowly in the furnace. Finally, the specimens were electropolished using an electrolyte of 5 parts ethyl alcohol and 1 part perchloric acid. Each specimen was approximately 5 in. in length and 0.125 sq in. in cross section. The average orientations of the 5 series of crystals studied are shown on the stereographic projection of Fig. 1. The crystals were strained approximately 2 pct in a soft tensile machine. The strain sensitivity was 3.6 x 10-4 cm over a 5-cm gage length.

Jan 1, 1960