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By J. D. Meakin, H. G. F. Wilsdorf

An etching technique.has been used to investigate the dislocation structure of deformed @-brass single crystals. Isolated single ended pileups have been observed, and it is shown that, in certain cases, the configurations of such pileups agree with theoretical predictions. Many discrete pileups within heavily deformed regions have also been detected and the influence of surrounding dislocations on these groups are reported and discussed. Divergences between the experimental and theoretical spacings in the isolated pileups and the origin of the stress maintaining the pileups are discussed. THE spatial configuration of a linear array of identical dislocations has been evaluated theoretically by Eshelby, Frank, and Nabarro.' Of particular interest is the equilibrium spacing of a series of dislocations under a uniform shear sti-ess when the leading dislocation is held fixed in the lattice; such an array is termed a single ended pileup. Eshelby, Frank, and Nabarro' found that an explicit analytical solution to the problem of n dislocations in a pileup is not possible, but they were able to derive approximate formulae applicable under various limiting conditions. An alternative method of determining the equilibrium configuration was proposed by Leibfried and Leibfried and Haasen in which the discrete dislocations are replaced by a continuous dislocation density. This technique was used by Head and Louat to solve in first approximation, a number of problems of particular interest, eg., single and double ended pileups. Head has also solved numerically a number of specific configurations involving up to six dislocations. Recently Kuhlmann-Wilsdorf has obtained numerical solutions for single-ended pileups containing between three and seventy dislocations, thus making possible a comparison between appropriate experimental results and accurate theoretical values. The considerable use of the pileup concept in theories of plastic flow has stimulated a number of attempts to observe such arrays experimentally. There is of course considerable intrinsic value in revealing an isolated pileup because a direct check on the elastic theory of dislocations then becomes possible. The only technique generally applicable for studying pileups in bulk metal specimens is selective etching of the point of emergence of individual dislocations. Confining our attention to etching studies which have revealed pileups, the earliest reported work

Jan 1, 1961

By M. C. Fuerstenau, A. M. Gaudin

Understanding the sedimentation of relatively thick suspensions depends on a knowledge of the concentration of the solids at various positions in the pulp and the times required for thickening. Flocculated kaolin slurries were studied with the transviewer, a device utilizing X-ray absorption in conjunction with a scanning mechanism. A mathematical model based on the Schuhmann size distribution in conjunction with Poiseuille's law yields experimental filtration rates as a hction of pulp density. These calculations show accord with the experimental results. Accurate predictions of sedimentation results depend upon determining the number and size of pores for given conditions, since the voidage of the suspension controls the volume of liquor that can pass through an element of suspension per unit time. A study on the sedimentation of flocculated kaolin slurries has indicated that their sedimentation takes place by two different processes, dependent on the initial concentration of solids in suspension. One process occurs in dilute suspensions (less than about 2 pct solids by volume) in which a multitude of relatively small flocs settle by hindered settling. In this case, maximal settling velocity is independent of container geometry.1 r2 The other process occurs in relatively concentrated suspensions (greater than about 2 pct solids by volume) in which the mass is considered to be settling as an aggregate network or as one large floc, defined as to size by the dimensions of the container. In this case, container geometry affects sedimentation results significantly. Furthermore, it seems that this single floc is in a state of compression from the beginning of settling, and that two phases of compression settling exist during sedimentation. The first occurs during the early stage of settling where liquid exudes easily and rapidly from the floc, while the second occurs in the compacting portion of the floc where water escapes more slowly and with much more difficulty. Sedimentation of relatively thick suspensions may then be thought to be a filtration phenomenon in which a pulp thickens by the filtration of its contained liquor through the aggregate network of pulp above it. This postulate has also been advanced by others.,4 To understand the sedimentation of relatively thick suspensions more fully, it was felt that knowledge of the concentration of solids at all positions in the

Jan 1, 1962

By W. D. Forgeng, R. E. Grace

The rate of copper corrosion in liquid lead was studied as a function of flow rate and temperature in a closed isothermal loop system between 350" and 500°C. Kinetic data were interpreted with the Nernst-Brunner equation and the Chilton-Colbum mass transfer analogy to heat transfer. Over the range of temperatures and flow rates employed the solution rate constant varied from 2 x 10-3 to 20 x 10-3 cm per sec. The rate constant was found to vary with the 0.76 power of the Reynolds number in the range 7500 < Re < 40,000. The results of this investigation indicate that the Cu-Pb corrosion process is controlled largely by diffusion across a boundary layer. particularly at the higher temperatures. The effective boundary layer for diffusion is found to be approximately three to four times smaller than the momentum boundary layer. CORROSION by liquid metals has long been a problem during melting, static containment, and casting. Recently, considerable emphasis has been placed on the understanding of liquid metal corrosion mechanisms in an effort to prevent mass transfer and eventual failure in liquid metal heat exchangers and in liquid-metal-fueled nuclear reactors. The present investigation was conducted to determine the relationships which exist between corrosion kinetics and hydrodynamic conditions in an isothermal loop containing a simple liquid metal-solid metal corrosion system. The Cu-Pb system was chosen for its simplicity and ease in handling. Previous isothermal Cu-Pb corrosion studies1-3 have been conducted in both static and dynamic systems but not under conditions which allow easy "scale-up" to engineering systems, such as liquid metal heat exchangers. On the other hand, most liquid metal loops which have been used to evaluate mass transfer rates4 have been driven with temperature gradients under conditions of natural convection and unknown flow rates. The primary contributions of this research are twofold: 1) to evaluate the design of a simple isothermal loop corrosion system and 2) to investigate liquid metal corrosion behavior under well-defined hydrodynamic conditions. MATERIALS AND EXPERIMENTAL WORK The apparatus used to measure the Cu-Pb corrosion rates is shown schematically in Fig. 1. The loop system consisted of 1) a reservoir made of Type 316 stainless steel containing a centrifugal pump and 2) stainless-steel tubing containing a removable copper test section. The copper test section was OFHC hard-drawn tubing, 11.0 0.05 cm in length and 0.775 ±0.005 cm ID. A Type 316 stainless-steel venturi meter* was inserted in place of the copper test sec- tion in order to determine the lead velocity as a function of pump speed at each temperature. The Cu-Pb system was chosen for this study because the solubility of copper in liquid lead is large enough to measure accurately but small enough that the diameter of the copper tubing was not changed significantly by corrosion. There are no intermediate phases formed in the system, and the solid solubility of lead in copper is vanishingly small so that back-diffusion cannot occur. Molten lead (corroding grade; 99.94+ pct Pb, 0.0015 max pct Cu) was charged from an auxiliary melting furnace into the system under an argon cover to minimize oxidation. The lead was then maintained at constant temperature by a stirred molten salt bath in which the loop was immersed to a depth just above the lead level in the reservoir, Fig. 1. The total volume of lead in the system was 320 2 cu cm.

Jan 1, 1969

By Walter Crafts, C. M. Offenhauer

In a previous study of the carbide phase of chromium steels, it was shown that chromium carbide (Cr7C3) is 2 more stable carbide than cementite (Fe3C) at tempering temperatures above about 500°C. in quenched steels containing from about I to 7.5 per cent chromium. Below this temperature the carbide phase was found to consist of cementite in all of the steels examined. In the present investigation it was found that a similar change in the carbide phase takes place in molybdenum and in chromium-molybdenum steels at approximately the same tempering temperatures. The approximate ranges of occurrence of the alloy carbides Cr7C3, Cr4C, and Mo2C have been determined in steels containing up to 5 per cent chromium, I per cent molybdenum and 0.60 per cent carbon. The experimental steels were made in small high-frequency furnaces from Armco ingot iron, low-carbon ferrochromium and calcium molybdate and were poured into 2-in. ingots, which were forged to I-in. round bars. Sections of the bars were heated to the carbide-solution temperature and cooled rapidly to induce austenite transformation at relatively low temperatures. The steels were subject to some segregation, therefore comparatively high temperatures were necessary to dissolve all of the carbides. The microstructure of the quenched specimens was examined to verify the belief that the carbides had been dissolved, and also to determine the nature of the nonmartensitic structure of incompletely hardened steels. Ferrite and pseudo-martensite were present in some of the specimens, but all specimens were quenched at such a rate that pearlite was not formed, in order to ensure the formation of the carbides at temperatures lower than about 500°C. It had been found previously1 that in chromium steels the chromium carbide could be produced by transformation of austenite in the pearlite range above 500°C., and, in order to start the tempering treatment with the carbide present as cementite, the absence of pearlite was considered to be essential. The specimens were tempered for 64 hr. to permit the formation of the stable carbide. After tempering, the specimens were submitted to microscopic and X-ray examination. The carbides were separated either electrolytically in a 5 per cent HCl electrolyte or with an acidified copper-potassium chloride solution. The crystal structure of the carbide phases was determined by the Debye-Scherrer type of X-ray patterns. The X-ray patterns obtained from specimens near the boundaries between two types of carbides were generally weak and diffuse as compared with the other patterns. For this reason, and because the more soluble components may be masked, the boundaries between the phases could not be determined precisely. However, the X-ray analysis of electrolytically separated carbides has given consistently reproducible results

Jan 1, 1943

By Walter Crafts, C. M. Offenhauer

In a previous study of the carbide phase of chromium steels, it was shown that chromium carbide (Cr7C3) is 2 more stable carbide than cementite (Fe3C) at tempering temperatures above about 500°C. in quenched steels containing from about I to 7.5 per cent chromium. Below this temperature the carbide phase was found to consist of cementite in all of the steels examined. In the present investigation it was found that a similar change in the carbide phase takes place in molybdenum and in chromium-molybdenum steels at approximately the same tempering temperatures. The approximate ranges of occurrence of the alloy carbides Cr7C3, Cr4C, and Mo2C have been determined in steels containing up to 5 per cent chromium, I per cent molybdenum and 0.60 per cent carbon. The experimental steels were made in small high-frequency furnaces from Armco ingot iron, low-carbon ferrochromium and calcium molybdate and were poured into 2-in. ingots, which were forged to I-in. round bars. Sections of the bars were heated to the carbide-solution temperature and cooled rapidly to induce austenite transformation at relatively low temperatures. The steels were subject to some segregation, therefore comparatively high temperatures were necessary to dissolve all of the carbides. The microstructure of the quenched specimens was examined to verify the belief that the carbides had been dissolved, and also to determine the nature of the nonmartensitic structure of incompletely hardened steels. Ferrite and pseudo-martensite were present in some of the specimens, but all specimens were quenched at such a rate that pearlite was not formed, in order to ensure the formation of the carbides at temperatures lower than about 500°C. It had been found previously1 that in chromium steels the chromium carbide could be produced by transformation of austenite in the pearlite range above 500°C., and, in order to start the tempering treatment with the carbide present as cementite, the absence of pearlite was considered to be essential. The specimens were tempered for 64 hr. to permit the formation of the stable carbide. After tempering, the specimens were submitted to microscopic and X-ray examination. The carbides were separated either electrolytically in a 5 per cent HCl electrolyte or with an acidified copper-potassium chloride solution. The crystal structure of the carbide phases was determined by the Debye-Scherrer type of X-ray patterns. The X-ray patterns obtained from specimens near the boundaries between two types of carbides were generally weak and diffuse as compared with the other patterns. For this reason, and because the more soluble components may be masked, the boundaries between the phases could not be determined precisely. However, the X-ray analysis of electrolytically separated carbides has given consistently reproducible results

Jan 1, 1943

During February there will be a meeting of the Committee on Technical Nomenclature of the Society for the Promotion of Engineering Education and representatives of the various engineering societies, to do the preliminary work necessary for the adoption of uniform lists of technical symbols. At this time it is expected that lists of symbols in general use throughout the country will be presented and the symbols most generally used will be recommended for adoption.

Jan 2, 1919

By L. A. Shipman

The combustion of coal in fuel beds has been practiced as an art for many years; during the last 2 7 years a scientific approach to this subject has contributed a small amount of fundamental data. The subject is a very controversial one. Opinions regarding the performance of the same coal used in the same equipment in different plants may vary from "the best coal ever used in the plant" to "the worst coal ever tired." These opinions can all be true, owing to the various conditions under which the coal was used. Because of these differences, an attempt will be made in this paper to discuss coal facts and coal characteristics as related to the use phenomena observed during the art of firing coal in fuel beds for many years. The work of Kreisinger1 and his associates in the 1,&apos;. S. Bureau of Mines, reported in 1916, was the first scientific attempt I know of to obtain factual data explaining the mechanism of combustion of fuel beds. They gave a chart showing an ignited fuel bed. The air passing up through the fuel bed first combined with the fuel by a reaction resulting in the complete combustion of carbon to CO2, which combined with the carbon in higher levels of the fuel bed to form CO with the absorption of heat. The fundamental facts produced in those experiments proved of much value and checked with practical experiences with hand-fired fuel beds. Hand firing was the prevailing method of stoking coal at that time. The order in which these reactions occur, as shown by Kreisinger and his associates, has been amply confirmed by repetition of this work with different fuels both her? and abroad. These experiments also showed that under their conditions the rate of burning was proportional to the air flow. These data were of practical value to a fireman and were accepted as generally true in all fuel beds. In later years many observations by myself in fuel beds of underfeed stokers and other thick fuel beds such as gas producers, where channeling. increase of particle size, or both, occur. indicated that, instead of the horizontal layers we had thought were present, perhaps the layers were vertical or irregular. Later investigations in fuel beds made by Mayers2 and Barnes3 indicated that the burning takes place in some instances along the surfaces of vertical or irregular channels or cracks in the fuel bed and that under these conditions a reaction occurs that differs from that in the old horizontal-layered handfired fuel beds. Examining the data in Kreisinger&apos;sl experiments, and the information in different charts with different fuels, different retort positions and air admissions of Barnes3 and the gas analysis arid isotherms of Mayers,2 one can check experience observation and come to a conclusion that as particle size of the fuel increases with other conditions the same, the maximum CO2 and temperature

Jan 1, 1947

By L. A. Shipman

The combustion of coal in fuel beds has been practiced as an art for many years; during the last 2 7 years a scientific approach to this subject has contributed a small amount of fundamental data. The subject is a very controversial one. Opinions regarding the performance of the same coal used in the same equipment in different plants may vary from "the best coal ever used in the plant" to "the worst coal ever tired." These opinions can all be true, owing to the various conditions under which the coal was used. Because of these differences, an attempt will be made in this paper to discuss coal facts and coal characteristics as related to the use phenomena observed during the art of firing coal in fuel beds for many years. The work of Kreisinger1 and his associates in the 1,&apos;. S. Bureau of Mines, reported in 1916, was the first scientific attempt I know of to obtain factual data explaining the mechanism of combustion of fuel beds. They gave a chart showing an ignited fuel bed. The air passing up through the fuel bed first combined with the fuel by a reaction resulting in the complete combustion of carbon to CO2, which combined with the carbon in higher levels of the fuel bed to form CO with the absorption of heat. The fundamental facts produced in those experiments proved of much value and checked with practical experiences with hand-fired fuel beds. Hand firing was the prevailing method of stoking coal at that time. The order in which these reactions occur, as shown by Kreisinger and his associates, has been amply confirmed by repetition of this work with different fuels both her? and abroad. These experiments also showed that under their conditions the rate of burning was proportional to the air flow. These data were of practical value to a fireman and were accepted as generally true in all fuel beds. In later years many observations by myself in fuel beds of underfeed stokers and other thick fuel beds such as gas producers, where channeling. increase of particle size, or both, occur. indicated that, instead of the horizontal layers we had thought were present, perhaps the layers were vertical or irregular. Later investigations in fuel beds made by Mayers2 and Barnes3 indicated that the burning takes place in some instances along the surfaces of vertical or irregular channels or cracks in the fuel bed and that under these conditions a reaction occurs that differs from that in the old horizontal-layered handfired fuel beds. Examining the data in Kreisinger&apos;sl experiments, and the information in different charts with different fuels, different retort positions and air admissions of Barnes3 and the gas analysis arid isotherms of Mayers,2 one can check experience observation and come to a conclusion that as particle size of the fuel increases with other conditions the same, the maximum CO2 and temperature

Jan 1, 1947

In the special number of the magazine Ocl und Kohle (Oct. 22, 1940) dedicated to the petroleum industry of southeastern Europe, there appeared several articles relating to Yugos1avia.t In the first article the author calls attention to the fact that there are two fields in Yugoslavia that have been explored and exploited by more than 100 wells at variable depths during the last 50 years. These are on the Island of Mura, at the confluence of the Mura and the Drave. Additional exploration drilling in various other parts of the country has been without result, but certain ones of these explorations have revealed the existence of gas horizons that have some value, which are being used for industrial purposes. Table I shows the production of oil and gas between the years 1900 and 1939. TaBle —Production of Oil ad Gas in Yugoslavia . n,i Natural Natural Years oil Years Gas, Cu. Years Gas, Cu. Meters Meters T900-1929 10,000 1923 507,000 1934 1,388,000 1930 277 1924 567,000 1935 1,401,000 1931 202 I92S 691,000 I936 1,483,000 t932 289 19261 1.472,000 1937 1,841,000 1933 629 1927! 1,732,000 193s 2,431,000 1934 324 1928 2,515,000 1939 2,628,000 1935 260 1929 4,700,000 1936 137 I93O 5.345,200 1937 463 1931 6,376,153 1938 1,091 1932 1,661,737 1939 1,114 1933 959,574 The number of wells drilled from 1884 to the present time was in the neighborhood of zoo and the total footage drilled was 65,000 m. up to July I940 They may be divided roughly as follows: 12 wells in the region produce natural gas; 134 wells in the two old fields of the Island of Mura and about zo wells for the exploration of the zone of the Flysch, in Bosnia. The depths of 50 of these wells was roo to 200 m.; the depths of 50 wells oil the Island of Mura ran from zoo to 500 m.; of 2 ; wells, 500 to I000 m.; of ro wells from rooo to 2000 meters. The deepest well drilling in Yugoslavia has reached 2000 in. In the Valley of Morave, in the region of Selnica, I00 km. south of Nish, there have been discovered asphalt-bearing limestones, which contain about 15 per cent asphalt and are associated with bituminous clays. Later, at Paclenica, important deposits of natural gas were found. A zone rich in gas and oil seepages runs through Pracec, Miklenska, Bujavica, etc. The author studied these regions from the point of view of stratigraphy and tectonics. The anticlines and gas-bearing domes are concentrated in two zones: the region of the Drave (Island of Mura) and the region of the Save, southeast of zagreb, which contains the gas field in exploitation in the region of Bujavica. A full description of the productive region of the Island of Mura has been given by Egon Bohm, a geologist, in the second article mentioned. This includes a history of the exploration and exploitation that took place under Hungarian rule in this region. The most important exploration was effected between 1884 and 1885 by Stavenov and Stinger, of Vienna. In 1927 work was done in the same region by Anton Raky, a well-known explorer who makes work of this kind his specialty.

Jan 1, 1941

In the special number of the magazine Ocl und Kohle (Oct. 22, 1940) dedicated to the petroleum industry of southeastern Europe, there appeared several articles relating to Yugos1avia.t In the first article the author calls attention to the fact that there are two fields in Yugoslavia that have been explored and exploited by more than 100 wells at variable depths during the last 50 years. These are on the Island of Mura, at the confluence of the Mura and the Drave. Additional exploration drilling in various other parts of the country has been without result, but certain ones of these explorations have revealed the existence of gas horizons that have some value, which are being used for industrial purposes. Table I shows the production of oil and gas between the years 1900 and 1939. TaBle —Production of Oil ad Gas in Yugoslavia . n,i Natural Natural Years oil Years Gas, Cu. Years Gas, Cu. Meters Meters T900-1929 10,000 1923 507,000 1934 1,388,000 1930 277 1924 567,000 1935 1,401,000 1931 202 I92S 691,000 I936 1,483,000 t932 289 19261 1.472,000 1937 1,841,000 1933 629 1927! 1,732,000 193s 2,431,000 1934 324 1928 2,515,000 1939 2,628,000 1935 260 1929 4,700,000 1936 137 I93O 5.345,200 1937 463 1931 6,376,153 1938 1,091 1932 1,661,737 1939 1,114 1933 959,574 The number of wells drilled from 1884 to the present time was in the neighborhood of zoo and the total footage drilled was 65,000 m. up to July I940 They may be divided roughly as follows: 12 wells in the region produce natural gas; 134 wells in the two old fields of the Island of Mura and about zo wells for the exploration of the zone of the Flysch, in Bosnia. The depths of 50 of these wells was roo to 200 m.; the depths of 50 wells oil the Island of Mura ran from zoo to 500 m.; of 2 ; wells, 500 to I000 m.; of ro wells from rooo to 2000 meters. The deepest well drilling in Yugoslavia has reached 2000 in. In the Valley of Morave, in the region of Selnica, I00 km. south of Nish, there have been discovered asphalt-bearing limestones, which contain about 15 per cent asphalt and are associated with bituminous clays. Later, at Paclenica, important deposits of natural gas were found. A zone rich in gas and oil seepages runs through Pracec, Miklenska, Bujavica, etc. The author studied these regions from the point of view of stratigraphy and tectonics. The anticlines and gas-bearing domes are concentrated in two zones: the region of the Drave (Island of Mura) and the region of the Save, southeast of zagreb, which contains the gas field in exploitation in the region of Bujavica. A full description of the productive region of the Island of Mura has been given by Egon Bohm, a geologist, in the second article mentioned. This includes a history of the exploration and exploitation that took place under Hungarian rule in this region. The most important exploration was effected between 1884 and 1885 by Stavenov and Stinger, of Vienna. In 1927 work was done in the same region by Anton Raky, a well-known explorer who makes work of this kind his specialty.

Jan 1, 1941

By M. A. Dayananda, R. E. Grace, P. F. Kirsch

Ternary diffusion experiments were carried out at 750°C with vapor-solid diffusion couples in single-phase copper-rich Cu-Zn-Sn alloys. The Philibert-Guy method was used to calculate intrinsic diffusion coefficients at compositions corresponding to the plane of inert markers imbedded in the diffusion couples. Inter diffusion coefficients were determined at common composition points of intersecting diffusion paths. Intevdiffusion coefficients were also obtained at compositions corresponding to maxima in the tin concentration pvofiles Relations between the interdiffusion coefficients and the expansion of vapor-solid diffusion couples are described in detail. Such relations permit the calculation of constant interdiffusion coefficients in binary couples from expansion data directly. In ternary couples expansion data provide an additional constraint on the interdiffusion coefficzents. ThE phenomenological analysis of diffusion in ternary solid solutions has been developed extensively, and various approaches taken in the determination of diffusion coefficients have been reviewed recently by Guy et al.&apos; Finite,&apos; semi-infinite,3 and infinite4 diffusion couples have been used in studies of ternary diffusion, but most of the work has been done with infinite diffusion couples. Semi-infinite diffusion couples3 (vapor-solid couples) have been used to determine both intrinsic and interdiffusion coefficients in the Cu-Zn-Mn system, in which two diffusing species, zinc and manganese, were supplied from the vapor phase. If only one component has a sufficiently high vapor pressure to be supplied from a vapor source, vapor-solid diffusion couples may still be used. In this case the boundary conditions at the gas/solid interface may be governed by partial equilibria rather than by virtually complete equilibrium between the phases. In the present work diffusion measurements were carried out at 750°C with vapor-solid couples of Cu-Zn-Sn alloys. Only zinc was transported between the vapor source and the diffusion disks, because the vapor pressures of both copper and tin are at least 108 lower than that of zinc. Both intrinsic and interdiffusion measurements were made at several compositions. A secondary objective was to relate expansion of the diffusion couples with the interdiffusion process. Such measurements for binary couples yield average values of the interdiffusion coefficients over composition increments. In ternary diffusion couples ex- pansion data provide an additional constraint on the interdiffusion coefficients. COMPOSITION-DEPENDENT INTRINSIC AND INTERDIFFUSION COEFFICIENTS As shown by Philibert and GUy5 the determination of intrinsic diffusion coefficients in a ternary system requires two independent diffusion couples containing marker planes with identical composition. In the case of vapor-solid couples such a requirement torresponds to two couples set up with the same vapor source exposed to two diffusion disks of different composition. Inert markers placed initially on the disk surfaces become imbedded during diffusion. If the pair of couples exhibits appreciable marker burial with marker planes of virtually the same composition, the intrinsic diffusion coefficient may be evaluated at the composition of the marker planes. Fig. 1 is a schematic diagram of the concentration of of a Cu-Zn-Sn ternary vapor-solid couple after diffusion of zinc from a vapor source into a binary Cu-Sn alloy. The areas, Ai correspond to the cumulative intrinsic fluxes of the three diffusing species across the marker plane:5 where Ji is the intrinsic flux of component i, t is the diffusion time, and D3i are the intrinsic diffusion coefficients. For the determination of interdiffusion coefficients a pair of diffusion couples with intersecting diffusion paths is needed. At the composition point of intersection (C1, C2) the coefficients are evaluated from the equation:3

Jan 1, 1969

By R. E. Reed-Hill, W. H. Hartt

The second order, {1011}-{1012} twin bands observed in critically deformed magnesium are often accompanied by an unusual form of kinking. These kinks, which lie adjacent to and run more or less parallel to the twin band habit, allow plastic deformation that occurs inside the twins to be accommodated into the matrix. The bend planes of these kinks cannot be explained using slip dislocations with Burgers vectors lying in the basal plane. A mechanism involving a single set of {1012)(1011) dislocations is proposed to account for the kink band habit, in good agreement with the experimental observations. It has been shown that second order, {101l)-{1012} twinning is an important phenomenon for magnesium deformed in the ambient temperature range. A detailed study of these twins has recently led to a better understanding of their irrational habit plane1 and their relation to fracture in magnesium.&apos; This paper is concerned with a third aspect of these twins; this being the kink bands, originally referred to as shear accommodation kinks,3&apos;4 that are often induced in the adjacent matrix. A twin band and its shear accommodation kink usually appear as a single macroscopic deformation, as seen in Fig. 1. The complex nature of these deformed regions is easily revealed, however, with the aid of a suitable microscope. It has been proposed374 that the primary function of these kinks is to accommodate the nonhomogeneous deformation that normally occurs in the second order twins. The twins tend to form as small discrete lamellae lined up approximately one in front of the other.&apos;&apos;&apos; Very large plastic deformations varying in magnitude from one twin to the next, may occur inside these lamellae. The kinks serve both to pass this strain into the matrix and to accommodate strain variations between twins. Deformation within the kinks, subsequent to their formation, has also been observed;3,4 and it is thought that this contributes to the strain accommodation process. The bend planes of the kinks have a habit near that of the twin band itself, which lies about 56 deg from the matrix basal plane. This orientation does not bisect the angle formed between the basal plane to either side of the bend plane and therefore differs markedly from the kink structure usually observed in hcp metals.&apos;-&apos; The present paper reports the results of a study of shear accommodation kinks and proposes a possible solution to the problem of the orientation of the bend plane. EXPERIMENTAL PROCEDURE Rectangular cross-section tensile specimens with axes parallel to (1010) and faces to (1210) and (0001) were cut and acid machined from a high-purity magnesium single crystal. After straining on an Instron machine the specimens were examined by both optical and replica electron microscopy. The basic procedures have been previously reported."&apos; EXPERIMENTAL RESULTS AND DISCUSSION Structure of Shear Accommodation Kinks. A typical, large (101l)-{1012) twin band with its associated shear accommodation kink is shown running diagonally from upper left to lower right in Fig. 1. In this optical micrograph the twin band, consisting of a row of small, highly deformed twin lamellae, is visible as a narrow dark band along the left hand edge of the structure in question. The kink lies to the right of the twins, is approximately three times as wide, and is lighter in contrast. The horizontal slip lines visible on the general specimen surface correspond to matrix basal slip and are parallel to the tensile axis. Note that on the right-hand side of the band these slip lines can be followed from the matrix into the kink. At the kink band boundary the slip lines suffer a clockwise rotation of about 25 deg. Rotations of this magnitude are not uncommon. When a surface such as that in Fig. 1 is given an etch1 making it sensitive to polarized light, it has been observed that the slip traces in the kink are parallel to the basal plane trace in this region. This is in excellent agreement with the assumption that these regions are indeed kinks. Fig. 2 is an electron micrograph of this same twin band and kink. Note that a row of small supplimation pits has formed

Jan 1, 1969

By C. S. Smith, L. Guttman

It is shown, from a study of geometric probabilities, that the average number of intercepts per unit length of a random line drawn through a three-dimensional structure is exactly half the true ratio of surface to volume. Since the surfaces can be internal or external, the area of grain boundary or of the interface between any two constituents in a micro-structure can be measured. Other metric relations are tabulated that may be of use in studies of the microstructure of polycrystalline, cellular, or particulate matter generally. IN many fields of scientific investigation the structure of cellular aggregates or random arrays of discrete particles imbedded in some matrix is observed on a two-dimensional section and inferences are drawn therefrom as to the real structure in three dimensions. The biologist&apos;s microtome slice, the petrologist&apos;s thin section, and the metallurgist&apos;s plane polished and etched sections are common examples, although the problem is a general one. Scientists have commonly limited their thinking to the same dimensionality as their structures, and the few attempts that have been strictly three-dimensional in character have been laborious and noteworthy. From a metallurgical standpoint it is often of considerable importance to know, in addition to the volume fraction of two or more components in an alloy, the amount of two-dimensional interface between crystals. Such grain boundaries (which may separate either two identical crystals differing only in orientation or two crystals differing in structure, and possibly also in orientation) have a determining factor upon the mechanical behavior. It is at these boundaries that melting commences, that stress-induced corrosion occurs, and that various precipitates (harmful or otherwise) first appear. The boundary is doubtless of equal importance in nonmetallic crystalline aggregates such as rocks, ceramics, and concrete, and the biologist is deeply concerned with the area of cellular membranes. Many synthetic cellular foams involve similar structural problems. The very term structure usually implies the presence of interfaces and a complete understanding of structure involves nothing but an analysis of the geometrical, metrical, and topological relations between the various interfaces (zero, one and two-dimensional) that exist in a three-dimensional structure. Even systems lacking sharp physical interfaces often have interrelated gradients of composition or velocity (as cored crystals or turbulence cells) in which a neutral surface can be treated as a two-dimensional interface. In an earlier paper by one of the authors&apos; the question of cell shape was considered in terms of simple topological principles without regard to physical dimensions. The determination of the actual size of grains in two dimensions is carried out in a routine fashion in innumerable metallurgical laboratories (see, for example, the ASTM standard methods of grain size determination2), though this is done merely to check the uniformity of a product and has no relation to the actual three-dimensional shape or size of the grains. Some authors have discussed the three-dimensional problem but only on the basis of assumptions as to idealized grain shapes.:&apos;-&apos; Quantitative measurements of microstruc-tures to obtain the volumetric relations of various phases have been carried out by petrographers for many years and are of increasing popularity among metallurgists." The present paper will show how, on the basis of no assumptions other than randomness of sectioning (usually realizable in experiment), it is possible to learn a great deal about the three-dimensional structure. The relations to be derived will generally be used on random arrays of cells or other particles, although they are equally applicable to ordered arrays and even to isolated objects of complex shape provided that suitable random sections can be made. Total Area of Interfaces in a Sample Consider a typical microstructure of a single-phase polyerystalline metal, such as that shown pres- in Fig. 1. The plane cross section shown contains a network of lines which subdivides the area into two-dimensional cells. The lines, of course, represent merely the intersection of the two-dimensional plane of sectioning with the two-dimensional interfaces between adjacent three-dimensional cells. The structure also contains points at which two or more lines intersect: in three dimensions the points are, of course, lines. In the more general case there may be in three dimensions isolated particles surrounded by a single interface without contact with others, and both two and one-dimensional features which do not necessarily connect with others. On the two-dimensional section these will appear as areas delineated by a closed line (as at a and b, Fig. 2), as isolated lines

Jan 1, 1954

An appropriation of $4000 was made to the United Engineering Society for the support of the work of the Engineering Council. It was resolved that the proposed amendments to the Constitution, regarding requirements for membership, be sent to the membership without comment thereon by the Board of Directors. Forty-one members, and three associates were elected. The status of two junior members was changed to member. The resignation of one member was accepted. The dues of nineteen members who are engaged in active duty with the Allied armies were remitted. B. B. Thayer was elected a member of the Board of Trustees of the United Engineering Society for a period of three years, to succeed himself. John H. Janeway was elected a member of the Library Board for a period of four years, to succeed himself. George C. Stone was elected a member of the Library Board in place of E. F. Roeber, deceased. E. Gybbon Spilsbury was elected representative of this Institute on the John Fritz Medal Board of Award, to succeed himself. J. Parke Channing was elected a member of the Engineering Council for a period of three years, to succeed himself.

Jan 1, 1918

By Owen W. Ellis, Telfer E. Norman

The use of cadmium as a base for bearing metals is one of the most interesting recent developments in this field. It has caused a strong demand for cadmium and a marked rise in its price. It appeared to the authors, therefore, that the situation might be relieved for users if acceptable substitutes could be developed. A preliminary investigation has revealed that to some extent mercury may be substituted for cadmium. Whether its use is justified cannot be stated at this time. Most of the authors&apos; work has indicated that the addition of mercury to alloys of cadmium and nickel detracts from their desirable physical properties; but this work has not been extended to cover service tests, which might reveal that the addition of low percentages of mercury to the cadmium-base alloys would improve their performance. The results of tests made by the authors are therefore briefly summarized for this paper. Table 1 gives the proportions of the metals used in preparing the alloys. After preparation of these alloys, th composition was checked by chemical analysis. Particular care taken to ensure that the nickel content did not vary appreciably from 1 per cent.

Jan 1, 1938

By Owen W. Ellis, Telfer E. Norman

The use of cadmium as a base for bearing metals is one of the most interesting recent developments in this field. It has caused a strong demand for cadmium and a marked rise in its price. It appeared to the authors, therefore, that the situation might be relieved for users if acceptable substitutes could be developed. A preliminary investigation has revealed that to some extent mercury may be substituted for cadmium. Whether its use is justified cannot be stated at this time. Most of the authors&apos; work has indicated that the addition of mercury to alloys of cadmium and nickel detracts from their desirable physical properties; but this work has not been extended to cover service tests, which might reveal that the addition of low percentages of mercury to the cadmium-base alloys would improve their performance. The results of tests made by the authors are therefore briefly summarized for this paper. Table 1 gives the proportions of the metals used in preparing the alloys. After preparation of these alloys, th composition was checked by chemical analysis. Particular care taken to ensure that the nickel content did not vary appreciably from 1 per cent.

Jan 1, 1938

The Joint Committee (consisting of the chairmen of the several society committees), formed under the authority of the five societies, in order to facilitate the carrying out of the organization of an engineer reserve as part of the military forces of the United States, for which work it was appointed, now begs leave to report as follows: .The Committee has been in personal communication with the Secretary of War, the officers of the General Staff, the officers of the War College, and with the Hon. George E. Chamberlain, Chairman of the Senate Committee on Military Affairs, and the Hon. James Hay, Chairman of the House Committee on Military Affairs. As the result of these interviews there has been incorporated in the draft of the legislation proposed by the Secretary of War and included also in the bills drawn by the committees of the Senate and of the House a provision for the organization of an officers reserve on broad lines, including an engineer reserve. As now drawn these bills provide that an officer shall be commissioned for a period of five years with rank up to and including that of major, after passing such requirements of character and qualifications as shall be prescribed by the President. The bill also provides that a certain amount of duty with pay shall he performed each year by the officers in the reserve. . The Committee is waiting for the Navy Department to formulate its plans for the increase in the naval forces, and as soon as a decision has been reached by that Department and the Committee is in possession of the facts, the Committee will take up the question of the organization of an engineer reserve for the navy, similar to that contemplated for the army.

Jan 2, 1916

By G. H. F. Gardner

The boundary conditions F = 1.0 and 4 = 1.0 (100 per cent) are dictated by the definition of F in the equation 1/F = aFp. These conditions have physical significance as the "limiting conditions" for the observed behavior in systems of dispersed particles. The other boundary conditions, cited by Gardner in his Eq. 3 as applying to this system, have no significance in the systems we studied. Maxwell&apos;s equation (Eq. 2) cited in Gardner&apos;s comments was developed for and limited to a regular, rather than random, dispersion of spheres which are sufficiently removed from each other so that they do not interfere with current flow about their neighbors. These restrictions also apply to Rayleigh&apos;s analysis. The title of Rayleigh&apos;s paper cited by Gardner is "On the Influence of Obstacles Arrayed in Rectangular Order upon the Properties of a Medium". He is not discussing randomly dispersed spheres. It might be inferred from Gardner&apos;s comments that Rayleigh specifically considered the differential equation (Gardner&apos;s Eq. 3). This is not the case. Mathematically, Gardner&apos;s Eq. 3 is exactly true for the system to which it applies, however, as both Rayleigh and Maxwell note that their equation for F in terms of F is not for randomly dispersed spheres. At the time we wrote our paper, we were aware of the work of Wyllie and Gregory as cited by Gardner. We cited their work in Ref. 5 of our paper. Our comment on page 287 of the paper about the validity of an m value of 1.3 for spheres with a porosity of 38 per cent remains as our answer to Gardner&apos;s question on this point. Our data, at 38 per cent porosity, show that the condition a = 1 and m = 1.3 holds for spheres near 40 per cent porosity.

By AIME AIME

AS one of his friends asserted at the Galveston meeting last fall, T. V. Moore is one of the "thinkers" in his field. He is head of production research for the Humble Oil & Refining Co., with headquarters in Houston. He is also known in the Institute as a "doer" for his active participation in the affairs of the Petroleum Division and for his leadership in the formation of the present Gulf Coast Section, A.I.M.E.

Jan 1, 1940

By AIME AIME

THE world was not quite ready for Hal Marsh when he emerged from the California Institute of Technology in 1922 with a Bachelor of Science degree in mechanical engineering, so, finding no promising job, he went back on a fellowship for another year. He wound up his responsibilities to it on a Saturday in June, 1923, went to work for the General Petroleum Corp. of California the next Monday morning, and has been there ever since. His present position is that of "production engineer." As such, his duties are miscellaneous and vague, but may mostly be described as investigation of equipment and methods pertaining to drilling and the production of oil, with occasionally a bit of design. He has written important papers for the A.I.M.E., American

Jan 1, 1936