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By M. R. Geer, H. F. Yancey

Coal washing assumed an important role in the mining industry of the Pacific Northwest long before washing practice became firmly established in the Appalachian field. A Scaife washer was operated in the state of Washington in 1887; and by 1927, the fist year for which complete statistics were compiled, nearly a third of the state's coal production was washed, in comparison with only about 5 pct for the country as a whole. Mechanical preparation was adopted in Alaska in 1922 in a plant constructed by the United States Navy at Chickaloon to provide bunker coal for naval forces operating in northern waters. Many of the coal beds mined in Washington and Alaska contained more impurities than those mined elsewhere, and this circumstance contributed to the early interest in mechanical cleaning. A much more important factor, however, was the inclination of the coal beds. With steeply pitching beds, hand sorting by the miner at the face is impossible; consequently, all material must be loaded and dealt with on the surface, just as is now proving the case with mechanical mining of flat beds. Thus "full-seam" mining afforded the same stimulus to the early development of coal washing in the Northwest that it is providing under mechanization in the rest of the country today. Objeet and Scope ' This report is intended to provide a general summary of the status of coal-washing practice in Washington, Oregon, and Alaska—an area in which some of the coals mined are more difficult to wash than those mined elsewhere in the country. Detailed flowsheets of plants, statistical data on production, and cost figures have been omitted, largely for the sake of brevity but also because such information is principally of only local interest. On the other hand, considerable washability data have been included because they are Washington At present Washington leads all other states in the percentage of its total production that is cleaned mechanically, 82.1 pct in comparison with the national average of 25.6 pct in 1945.' The washing problems encountered in this state are highly variable because the mountain-building forces that created the Cascade Range caused such intense folding and faulting of the beds in some fields that the rank of the coal was increased to anthracitic, while in other fields more distant from the mountains the beds were relatively undisturbed, and the rank of the coal ranges down through subbituminous to lignitic. The complicated and burdensome schedule of sizes prepared in most coal fields has never been required by the Washington market. With but few exceptions, lump is prepared on a round-hole screen of about 3 in. size, egg is about 3 to 1 5/8 or 1½ in., and nut is 1 5/8 or 1½ in. to either 1 or ¾ in. Some mines screen no finer than ¾ in. and market a slack coal of that top size, but generally the coal is screened at about ¼ in. to give a stoker coal of ¾ or 1 to ¼ in., and a ¼ in. to 0 "buckwheat." During recent years the market for lump coal has largely disappeared, and lump is crushed to supplement the pro-

Jan 1, 1950

By David B. Reger

The expansion of the previously discovered gas pools and an intensified search for additional pools in the Oriskany and deeper sands were the principal petroleum activities in West Virginia during 1941. One small oil pool was discovered and another was considerably extended. One small gas pool was discovered, several isolated well discoveries were expanded into definite pools, and various recognized pools were substantially increased. The proved oil territory of the state was increased about 600 acres and the proved gas territory about 45,000 acres. The new discoveries of oil did not equal withdrawals but gas reserves added were greater than gas withdrawals. Oil activity, as in the past several years, was slight because of unfavorable crude prices. Most operators prefer to leave oil in the ground rather than to drill for it without a better return. Gas activity increased greatly because of better demand, even though the price of gas did not improve. The account of operations, as gathered from trade journals and other reporting services, shows that 838 new wells were drilled, resulting in 114 new oil wells with 2606 bbl. of daily new production; 558 new gas wells with 949,226,000 cu. ft. of daily open flow; and 166 dry holes. Also, 86 old wells were drilled to deeper sands with 9 bbl. and 56,030,000 cu. ft. of added production. On the new wells the oil average was 22.86 bbl. per well per day; and the gas average was 1,701,000 cu. ft. per well per day. On new wells the ratio of dry holes to completions was 13.61 per cent. On deeper drilling to other sands the ratio of failures was 15.12 per cent. From an exploratory standpoint one strictly new oil pool (Higginbotham Run) was opened in Kanawha County and one strictly new gas pool (Lost Run) in Taylor County. One entirely isolated wildcat gave commercial Oriskany-sand gas production and may open a pool. Various other wildcats greatly extended the boundaries of known Oriskany-sand gas pools and various others may have opened new pools in the shallow sands. On the other hand, various Oriskany tests in Harrison, Monongalia, Roane and Wood Counties were dry and all five tests to the White Clinton sand (Sil.) in Boone, Harrison, Kanawha and Wood Counties failed to find commercial production. The principal oil wells completed, by counties, were: Calhoun, 24; Clay, 7; Gilmer, 6; Hancock, 9; Kanawha, 9; Pleasants, 10; and Ritchie, 14. Production for the year was estimated by the Oil Weekly as 3,421,000 bbl., compared with U. S. Bureau of Mines final figures of 3,444,000 bbl. in 1940. The leading counties in gas-well completions were: Boone, 32; Braxton, 19; Cabell, 16; Calhoun, 46; Clay, 20; Gilmer, 37; Jackson, 94; Kanawha, 82; Lincoln, 17; Putnam, 46; Ritchie, 33; Upshur, 20; and Wayne, 33. Production for the year is estimated by the author as 210,000,000,000 cu. ft., as compared to the U. S. Bureau of Mines' final figures of 188,751,000,000 cu. ft.* in 1940.

Jan 1, 1942

By David B. Reger

The expansion of the previously discovered gas pools and an intensified search for additional pools in the Oriskany and deeper sands were the principal petroleum activities in West Virginia during 1941. One small oil pool was discovered and another was considerably extended. One small gas pool was discovered, several isolated well discoveries were expanded into definite pools, and various recognized pools were substantially increased. The proved oil territory of the state was increased about 600 acres and the proved gas territory about 45,000 acres. The new discoveries of oil did not equal withdrawals but gas reserves added were greater than gas withdrawals. Oil activity, as in the past several years, was slight because of unfavorable crude prices. Most operators prefer to leave oil in the ground rather than to drill for it without a better return. Gas activity increased greatly because of better demand, even though the price of gas did not improve. The account of operations, as gathered from trade journals and other reporting services, shows that 838 new wells were drilled, resulting in 114 new oil wells with 2606 bbl. of daily new production; 558 new gas wells with 949,226,000 cu. ft. of daily open flow; and 166 dry holes. Also, 86 old wells were drilled to deeper sands with 9 bbl. and 56,030,000 cu. ft. of added production. On the new wells the oil average was 22.86 bbl. per well per day; and the gas average was 1,701,000 cu. ft. per well per day. On new wells the ratio of dry holes to completions was 13.61 per cent. On deeper drilling to other sands the ratio of failures was 15.12 per cent. From an exploratory standpoint one strictly new oil pool (Higginbotham Run) was opened in Kanawha County and one strictly new gas pool (Lost Run) in Taylor County. One entirely isolated wildcat gave commercial Oriskany-sand gas production and may open a pool. Various other wildcats greatly extended the boundaries of known Oriskany-sand gas pools and various others may have opened new pools in the shallow sands. On the other hand, various Oriskany tests in Harrison, Monongalia, Roane and Wood Counties were dry and all five tests to the White Clinton sand (Sil.) in Boone, Harrison, Kanawha and Wood Counties failed to find commercial production. The principal oil wells completed, by counties, were: Calhoun, 24; Clay, 7; Gilmer, 6; Hancock, 9; Kanawha, 9; Pleasants, 10; and Ritchie, 14. Production for the year was estimated by the Oil Weekly as 3,421,000 bbl., compared with U. S. Bureau of Mines final figures of 3,444,000 bbl. in 1940. The leading counties in gas-well completions were: Boone, 32; Braxton, 19; Cabell, 16; Calhoun, 46; Clay, 20; Gilmer, 37; Jackson, 94; Kanawha, 82; Lincoln, 17; Putnam, 46; Ritchie, 33; Upshur, 20; and Wayne, 33. Production for the year is estimated by the author as 210,000,000,000 cu. ft., as compared to the U. S. Bureau of Mines' final figures of 188,751,000,000 cu. ft.* in 1940.

Jan 1, 1942

By R. M. Brick, J. T. Richards

Tests have been conducted to determine the mechanical properties of several beryllium copper alloys down to liquid air temperatures. The materials investigated include beryllium copper, beryl-lium-cobalt-copper, and beryllium-zinc-copper in the wrought and cast conditions. As a means of evaluation, the influence of cold work and age hardening treatment upon subzero behavior has been observed. The effects of temperature upon both elastic and plastic deformation are also considered. THE low temperature mechanical properties of beryllium copper are of current interest in view of the increasing number of subzero applications. At extremely low temperatures, beryllium copper components are employed in temperature control and gas liquefaction equipment. At more moderate temperatures, such as those encountered in arctic regions, these alloys find use in a wide range of civilian and military applications. Although several previous subzero investigations have included beryllium copper,'-' none have been complete with respect to test temperatures or materials employed. As indicated in Table I, the alloy: used by Colbeck and MacGillivray,1 Walle,2 and Kostenets' were nonstandard and were not representative of present commercial practice. In addition, Kostenets4 did not test age hardened specimens, while the temperature in the other investigations", "-' were not carried below —100°F. These tests, however, indicate that beryllium copper offers interesting possibilities in subzero atmospheres, since the increase in strength with decreasing temperature is not accompanied by a reduction in ductility or impact resistance. As a means of checking and extending this earlier work at subzero temperatures, an investigation was undertaken at the University of Pennsylvania. In addition to testing the standard 2 pct beryllium copper, other alloys were also considered in wrought and cast forms. Charpy impact and tension tests were included with particular emphasis on the elastic characteristics, since beryllium copper is frequently selected for its spring qualities. Nominal test temperatures were +80°, —75", —200°, and —300°F. Test Materials Wrought beryllium copper, beryllium-cobalt-copper, and beryllium-zinc-copper specimens were machined from 0.560 in. diameter rod. These alloys were tested in the solution treated, cold drawn, or age hardened conditions. In the case of solution treated beryllium copper, some specimens were aged (3 hr at 600°F) for maximum hardness and others were overaged (1 1/2 hr at 750°F) to determine the effect of heat treatment. The compositions and average room temperature properties of these wrought alloys are presented in Table 11. The casting alloy versions of beryllium copper and beryllium-cobalt-copper were prepared as sand-cast cylinders, roughly 3/4 in. diameter x 6 in. long. Test specimens were machined from these cylinders. Conditions tested included as cast as well as solution treated and age hardened. Table 111 lists compositional and room temperature property data for the cast alloys. Test Methods Tension tests were conducted on specimens having a 0.25 in. diameter reduced section over a 1 in. gage length. To insure axiality, specimens were loaded by means of hardened chains. The yield strength at 0.2 pct offset was obtained from autographically recorded stress-strain curves resulting from a spe-

Jan 1, 1955

By Nicholas J. Grant, Italo S. Servi

THE creep and stress rupture properties of three grades of aluminum have been reported in a previous paper.' It was found that the stress coefficient of the creep rate and of the rupture time changes at the transition from low temperature-type to high temperature-type deformation. The transition corresponds to the equicohesion for grains and grain boundaries. In order to support the conclusions obtained from the examination of creep and stress rupture data, the deformed specimens were observed metallographically and a few special tests were conducted. The results of these qualitative observations are given in the present paper. Experimental Procedure and Results Table I gives the types of aluminum specimens.' The creep and stress rupture tests were conducted in simple tension at constant stress. Further details on the experimental techniques have been given.' The test bars were electropolished in a perchloric-acetic mixture before testing and were observed after testing without any further preparation unless otherwise specified. Observations of specimen cross-sections were made after electrolytic polishing and etching. The samples were extended along a direction parallel to the longer side of the micrographs of Figs. 12 through 27. The log-log plots of stress vs. minimum creep rate for the three grades of aluminum appear in Figs. 1 and 2. The reference numbers on each curve help relate the photographs to the conditions of testing, indicating where high temperature-type deformation and failure prevailed and where low temperature behavior prevailed. Deformation of Single Crystals at Very High Temperature: An annealed, high purity aluminum specimen was slightly strained at one end and re-annealed. A large single crystal was formed at the strained end of the specimen during re-annealing; the other end remained polycrystalline (see Fig. 3). A stress of 50 psi was applied to the cold specimen to avoid loading at 1100°F. The temperature was then raised to 1100°F, kept at 1100°F for 3 hr, and lowered again to room temperature. Fig. 4 shows the appearance of the specimen after testing. The single crystal deformed by gliding along parallel planes, while the polycrystalline part deformed mainly by grain boundary flow. Some grain growth occurred in the polycrystalline part. Another high purity specimen, which had two large single crystals at the two ends and a polycrystalline zone in the middle portion, was tested at 1000 °F under a stress of 100 psi. The appearance of the sample after test is shown in Fig. 5. Even though considerable slip occurred in the single crystals, the fracture occurred in the weaker polycrystalline portion. Evidence of Grain Boundary Migration during Creep Testing: A high purity, coarse grained specimen, which had a large crystal in the middle portion (see Fig. 6) was tested at 700°F under a constant stress of 175 psi for 30 hr. The appearance of the specimen after testing (Fig. 7) indicates that the large crystal deformed by gliding along parallel planes, while the rest of the specimen deformed mainly by grain boundary flow. Microscopic examination showed clear evidence of grain boundary flow and grain boundary migration, an example of

Jan 1, 1952

By J. P. Heller, H. B. Bradley, A. S. Odeh

A potentiometric model technique is presented for determining the areal sweep efficiency of a five-spot well pattern, at and beyond breakthrough. A sharp interface between displaced and displacing fluids is assumed. Although the prototype svstem is referred to as a waterflood operation, obvious changes in the notation and computations will adapt the results to other displacement processes. The results of the study include the following. 1. Areal sweep efficiencies for a five-spot well pattern, at and beyond breakthrough, for mobility ratios (displacing to displaced fluid) of 4:1, 2:1, 1:1 and 1:4. 2. Extension of potentiometric analysis to the investigation of the areal sweep efficiency beyond breakthrough in a five-spot pattern by the application of conformal mapping and conductive-solid models. 3. The use of layers of conductive fabric in representing mobility ratio changes in potentiometric models. 4. The development of a probe mechanism for probing conductive solids. The results obtained by conductive-cloth models agree with earlier areal sweep efficiencies at breakthrough obtained by Aronofsky and Ramey 1 on the potentiometric analyzer using electrolytic-tank models. Results beyond breakthrough differ from those obtained by the X-Ray Shadowgraph technique. Data from this study show that, for mobility ratios greater than one, water cut rises rapidly as fluid is produced after breakthrough. However, for mobility ratios smaller than one, a large increase in area swept resulted with only a small increase in water cut. INTRODUCTION In calculating reservoir performance of waterflood-ing operations and other fluid-injection programs, it is necesssary to estimate the areal sweep efficiency * before and after injected-fluid breakthrough into production wells. Influence of mobility ratio on oil-production history, before and after breakthrough for a five-spot well pattern, has been studied by X-Ray Shadowgraph techniques 2-5 and by gelatin models.6 In none of these investigations was the transition zone controlled experimentally. Steady-state anaiog techniques assume that a vertical and discrete interface exists between the displacing and displaced phase. Thus, when using a potentiometric analysis, it is assumed that no transition zone exists. To determine the areal sweep efficiency beyond breakthrough for a five-spot well pattern using the potentiometric analyzer, four principal problems had to be resolved. These were the following. 1. The laborious method of representing changes in mobility ratio in electrolytic tanks by means of contoured wooden blocks. 2. Vapcrization of the electrolyte solution during the study causing concentration changes and, thereby, variable conductivity. 3. The scale-limitation problem 7 that is accentuated by abrupt eiectrolyte depth changes. 4. A wellbore geometry problem. EXPERIhlENTAL EQUIPMENT AND PROCEDURES CONDUCTIVE-SOLID MODEL The theory, equipment and procedural techniques of the electrolytic-tank potentiometric model have been treaced excellently by Lee8 and by Muskat.9 By the use of a conductive solid to represent the fluid conductivity of the porous media, the need for contouring wooden blocks to represent mobility ratio was eliminated. It was found that a carbon-black coated fabric, Uskon D-16,** could be employed as a fairly uniform conductive media. This material, when stacked in appropriate layers and pressed together, can be used to represent changes in mo-

By S. S. Solomons, V. H. Tillmann, L. Smaniotto

INTRODUCTION The Zinc Corporation, Limited and New Broken Hill Consolidated Limited (ZC/NBHC) mines are situated at Broken Hill, New South Wales, Australia (refer Fig. 1). Both companies are wholly owned subsidiaries of Australian Mining and Smelting Limited (AM&S). Annual production from both mines is 2.3 million tonnes of lead, silver and zinc ore mined by a variety of underground methods. From 1911 to 1968, conventional overhand cut and fill stoping (both open and square set timber) was used almost exclusively, though some trials with shrinkage and sublevel stoping were undertaken. The trial stopes used short holes in conparison with today's sublevel open stopes. Mechanised cut and fill methods with regular rockbolt support were introduced in the early 1960's and undercut and fill stoping replaced square set timber stoping for pillar extraction in the late 1960's. Since 1968, increasing emphasis has been placed on longhole open stoping (LHOS) although some areas of the orebodies are comrnrnitted to the abovemehtioned methods since existing stope development makes it impracticable to change. In 1979, approximately half the total production was mined by LHDS and it is expected that the LHOS proportion will increase in the future. A vertical crater retreat method of longhole mining has also been successfully introduced to replace the undercut and fill stoping of some pillars and it is expected that this stoping method will be used in some future primary ore extraction. This paper reviews the progress of LHOS technology at ZC/NBHC with emphasis on the stope planning and design process and the importance of rock mechanics applications. The objective has been to maximise the primary extraction of the orebody giving due consideration to stability and safety. This has led to the design of a novel sloped wall longhole stoping method which should eliminate the formation of pillars by mining the orebody in a "continuous" manner incorporating a sloped sand interface between the blocks of ore being mined and the previously mined sandfilled stope. The expected results include the complete extract of the orebody without the formation of pillars and with minimal dilution of ore with sandfill. The evolution of the method can be best illustrated by following the mining progress of the relatively new Southern 'B1 Lode orebody at the NBHC mine. GEOLOGY Southern '8' Lode is the southern extension of the 'Bt Lode orebody, which is currently being mined further to the north in ZC/NBHC (refer Fig. 2). The ore block being developed and stoped extends for a vertical height of 90 metres from No. 17 level down to approximately ten metres above No. 19 level. The ore minerals are sphalerite and galena with the zinc:lead ratio averaging approximately 3:l with a minor amount of silver associated with the galena. There is a sharp contact between the ore and the country rock on the footwall and keel, while the hanging wall gradates into medium and low grade material. The gangue is primarily quartz together with garnet, biotite, feldspar, gahnite, sericite and minor apatite. In various horizons within the orebody, grey feldspar, quartz and garnet pegmatites occur as stratiform layers. The ore and country rock are competent with some inconpetent boundaries.

Jan 1, 1981

By J. W. Edington

THE Hopkinson bar has become a popular technique for the measurement of the mechanical properties of materials deformed at high strain rate. Maximum use of the equipment is made in the arrangement first used by Kolskyl in which a short compression specimen is sandwiched between two pressure bars and is loaded by a single pulse travelling through the system. The pressure bars are used both to apply the load to the specimen and as transducers to obtain continuous strain-time histories of three pulses, incident on, reflected, and transmitted by the specimen. The data measured by the pressure bars can be analyzed in terms of the stress/strain behavior of the specimen.2'3 However, one of the assumptions of the analysis of the observed pulses is that the total stress and total strain do not vary significantly from point to point within the specimen at any given instant during the deformation process. Although this assumption is generally justified for very short disc-like specimens2 the situation is uncertain for larger specimens. For example, at small plastic strains (-0.01) Hauser et al.2 have some evidence of small flucations in the total stress within the crystal during deformation, even in relatively short aluminum specimens. In addition, Karnes4 has shown that the plastic strain, and by inference strain rate, is different at each end of a compression specimen tested in a Hopkinson bar, although the length of the specimen was not specified. Recently, the mechanical properties and the dislocation substructure have been investigated in single crystals of columbium5 (length 0.25 in., diam 0.19 in.), and copper6 (length 0.5 in., diam 0.5 in.) deformed at high strain rates. As part of this research program the assumption that the plastic strain is constant throughout the specimen has been checked by measuring the total dislocation density as a function of position in the specimen. Compression specimens of the same orientations and dimensions were tested as described previously5,6 sing a split Hopkinson bar. Since any discontinuity in strain distribution is most likely to arise during the initial stages of deformation the investigation was performed on specimens deformed to plastic shear strains of 0.054 (copper) at a strain rate 1.2 x l03 sec-1, and 0.06 (columbium) at a strain rate 1.5 X l03 sec-1. The orientation of the single crystals is shown in Figs. 1 and 3. Thin foils were taken parallel to the most highly stressed slip plane, i.e., (111) in copper and (011) in columbium, using conventional disc techniques. The dislocation densities were measured using first order reflections with compensation for invisible dislocations.5'6 In the copper single crystals the discs were randomly distributed throughout the cross section of the specimen. However, the dislocation density obtained from each disc was plotted vs the disc positions relative to the ends of the specimen. The results for the copper specimens are shown in Fig. 1. Clearly the dislocation density is constant throughout the main portion of specimen within the experimental error. The error bars on the dislocation densities correspond to a shear strain variation of 0.015 on the basis of previous measurements% ± of the rate of increase of dislocation density with strain in copper single crystals of the same geometry. Thus within this experimental error the plastic strain can be concluded to be constant within the specimen and the assumptions used in the analysis of the stress/time curves are therefore reasonably valid. The higher measured dslocation density near the impact end and the lower dislocation density at the bar end of the copper specimen is in agreement with the results of Karnes4 who showed that this strain/time curve rose to a maximum more rapidly at the impact end compared with the bar end. Hauser et al.2 have also pointed out that at small plastic strains (-0.01) the strain at the impact end of the specimen may be greater than that at the bar end. Thin foils taken from different points within the columbium single crystals demonstrated that the dislocation density could vary significantly within the specimen, see Fig. 2. Large areas of some thin foils up to 30 µ sq contained very few dislocations, see Fig. 2(a). However, in other parts of the compression specimen dislocation configurations like those shown in Fig. 2(b) existed over large areas (-30 µ sq). As a result, when the average dislocation density in a thin foil is plotted as a function of the position of the thin foil relative to the ends of the specimen, considerable scatter is observed, see Fig. 3. In this material then, the local dislocation density, and consequently the

Jan 1, 1970

By H. O. Jahns, R. A. Greenkorn, R. E. Haring, L. K. Shallenbarger

This paper is a study of the effects of heterogeneity on flow in an analog of porous media, the Hele-Shaw model. l-3 A set of experiments in heterogeneous Hele-Shaw models showed streamlines through and around heterogeneities of various sizes, shapes and levels. (A level, we define as the ratio between the transmissibility of the heterogeneity and that of the rest of the model.) The heterogeneities were restrictions or expansions of the flow stream analogous to variations in the transmissibility of porous media. The experimental data agreed well with numerical results and with an analytical solution, which we derived for a circular heterogeneity in an infinite field. This study considers the flow-stream distortion due to the shape, size and level of heterogeneities. Size and level are much more important than shape provided the heterogeneity is not long and narrow. Our analytical solution shows that a circular heterogeneity in a large field can be replaced by an equivalent circle of either zero or infinite permeability. The radius of the. equivalent circle is a simple function of size and level of the actual circle. INTRODUCTION With the availability of high-speed computers and numerical procedures to predict reservoir behavior, we are faced with an important question. How much information about the reservoir do we need to justify the cost of the computer in any given case? To answer this question, we have to know how various reservoir parameters affect flow behavior. Reservoir heterogeneity is one of these parameters. In this study, we used a simple, two-dimensional model of porous media, the hele-shaw model, to investigate the effect of heterogeneity on flow behavior. We restricted ourselves to linear, single-phase, steady-state flow in a rectangular field with a single heterogeneity at its center. The analogy between flow in Hele-Shaw models and in porous media is easily verified. Let us first consider a homogeneous Hele-Shaw model with constant plate separation h. (The Hele-Shaw model is constructed by placing two plates, usually glass, very close together and allowing liquid to flow between them. Streamlines are made visible by introducing colored fluid into the space between the plates at a number of points across the model.) We assume a cartesian coordinate system with its origin in the middle between the plates and the z axis directed perpendicular to the glass plates (Fig. 1). The fluid flow is always in a direction parallel to the glass plates and varies from a maximum value to zero in the very small distance from the middle (z = 0) to either plate (z = h/2). For slow motion of an incompressible fluid, neglecting inertia and body forces, we have the viscous flow equation: where p is the fluid pressure, p the viscosity, and v the velocity vector with components u, v and w in the x, y and z directions, respectively. In our rase. and the derivatives of 3 with respect to x and y are small as compared with the derivative in the z direction. Therefore, approximately, with Vp and v being two-dimensional vectors in the x-y plane. Two integrations with respect to z give

Jan 1, 1965

By D. B. Jugle, J. B. Darby

The equilibrium solubility limits of the transition elements Ti, V, Cr, Fe, and Co in liquid tin were determined in the temperature range from 827" to 1211°K. Since the equilibrium concentration of Ti, V, or Cr in liquid tin is moderately dilute in the temperature range investigated, the solubility data were employed to estimate the partial molar enthalpy and the partial molar excess entropy of solution for the three solutes in liquid tin. The reference state s for titanium or vanadium were selected relative to the solute in an intermetallic compound. The thermodynamic quantities for chromium were calculated relative to pure chromium. RECENT experiments1 have shown that the rate of solution of several transition elements in liquid aluminum can be qualitatively predicted from a knowledge of the temperature dependence of the solvent-rich liquidus. In order to extend the analysis to binary tin systems,' it was necessary to know the equilibrium solubility of several of the first-long-period transition elements in liquid tin. Since solubility data for the tin-rich portion of binary systems are meager, the present investigation was undertaken to determine the equilibrium solubility limit of Ti, V, Cr, Fe, and Co in liquid tin in the temperature range from 850" to 1200°K. EXPERIMENTAL PROCEDURE A useful technique3 to determine the equilibrium solubility of a solute in a liquid-metal solvent consists essentially of placing a pure solute in contact with a pure solvent and allowing sufficient time for equilibrium to be attained at the temperature of interest. Subsequently, the solvent is removed and the equilibrium solute concentration in the solvent is determined by an appropriate analytical procedure. The technique can be applied very successfully to relatively simple systems such as the copper-germanium system.3 However, in many binary systems of transition elements with tin, several intermediate phases are known to exist and precipitation of the phases from solution, in solubility experiments, can lead to an erroneously large solubility. The difficulty was avoided in the present work by equilibration of the most solvent-rich intermediate phase with the pure solvent over a range of temperatures. The compounds employed in this investigation, and the temperature range over which each compound is in equilibrium with liquid tin are listed in Table I. No stable intermediate phases are reported in the chromium-tin system4 and, therefore, pure chromium was utilized as the solute. The stoichiometric compounds were prepared by arc-melting on a water-cooled copper hearth in a helium-argon atmosphere. The elemental tin employed in.this investigation was 99.998 pct pure, and typical lot analyses of the transition elements were reported elsewhere.' A sample of an appropriate solute, in the form of a button and in sufficient quantity to exceed the equilibrium solubility, and the pure tin solvent were placed in a high-purity recrystallized-alumina crucible. The crucible and contents were placed in a horizontal furnace under a high vacuum (10-6 torr) and held at temperature for periods varying between 24 and 72 hr. A water-cooled quench tank, partially filled with diffusion-pump oil, was attached close to one end of the

Jan 1, 1970

By M. S. Azun

I do not at all agree with the basic points of the author's conclusion. The use of lognormal or normal model to respond to the attribute distribution function should be carefully questioned. If fitting a distribution function of regionalized variables is the main purpose, one may employ one of certain well-known families of distributions, such as Tukey's lambda functions. For instance, the distribution function of gold assay values studied by Krige (Krige, 1978) may fit the lognormal model well, but one should not exclude that the basic idea of using the distribution function of observed data is to have insight of the physical mechanism that gives rise to the regionalized variables. In Applied Geostatistics, there are many examples considering only lognormal or normal model for the distribution function of geostatistical data even if the observed distribution function has more than one mode. Of course, using lognormal or normal model always brings easy computation for the statistical properties of attribute under investigation. Still, I object to adopting any of those models without having any "statistical inference." As seen from the author's paper, lognormal and normal model produce the same average grade (0.746% copper) and almost the same sample variance. Therefore, which model explains the probabilistic behavior of ore deposit is always an important question that should be replied by the geostatistician using not the common sense but the statistical and probabilistic methods. For kriging procedures, such as linear kriging, one should describe either second order stationary properties or bivariate properties of regionalized variables. Second order properties, such as correlogram function or semivariogram function, are the inputs of the so-called kriging equations. Selecting one of any useable models for the observed second order properties, such as spherical model, is not easy since the models are not based on the correlations structure of the regionalized variables. How those models being used in Applied Geostatistics can be distinguished is another important problem. One may develop many fitting models to respond to the observed second order properties of regionalized variables. However, I suggest that the model should be based on the probabilistic behavior of geologic process. The author used spherical model for copper, wolfram, and silver grades from isotropic sector (Fig. 2, 4, 3b) and exponential model for silver grades obtained along raises in isotropic sector (Fig. 3a). It seems that those semivariograms given in Fig. 3b for isotropic sector and Fig. 4 may be described by the random model implying that regionalized variables do belong to renewal process (Azun, 1983). If I knew the total number of data points used in estimation, may prove that my conclusion is correct. Recalling the test for the first order sample correlogram value, the test procedure is introduced such that the independence is rejected if [Ir(1) I > Za/2 N1/2] where Za/2 is the a/2 percentile of standard normal random variable and N is the total number of samples used in estimation (Azun, 1983). For the other observed semivariogram functions I suggest the author might try to use the so-called "Markovian model" describing not only the correlation structure of regionalized variables, but also the physical mechanism that produces the regionalized variables. The Markovian model for correlogram function is, [p (h) = T 1ih , h>1 ,] The Markovian model for the other second order properties of ReV are also derived. [T veß], in the above equation, show, for example, structural change and mineralizational variation in a considered deposit, respectively (Azun, 1983). In selecting any model, it is not easy to search for the "best" response to the observed second order properties of ReV's. The Markovian model, based on a theoretical understanding of underlying mechanism, gives more information about the occurrence of regionalized variables and respond to all properties. Random model and the so-called hole effect structure can be easily defined as a special form of the Markovian model (Azun, 1983). An estimation of any second order properties of regionalized variables may be computed through (N-1) lag. However, the dependency between the regionalized variables may be deemed to have "died out" after the so-called stationarity width (range). In practice, the estimation is carried out through 25% of the total number samples available. Therefore, the large fluctuations around the zero level and variance for correlogram or covariogram function and semivariogram function, respectively, cannot be observed. Since the number of pairs involved in the estimation of higher second order properties is small, the estimation variance at those lags is large. There is no need to show higher order estimated second order properties. After using one of any kriging procedure for block estimation, the distribution function of average grades has the same mean as the drilling sample grades but

Jan 1, 1986

By G. C. Kuczynski

Two particles in mutual contact form a system which is not in thermo-dynamical equilibrium, because its total surface free energy is not a minimum. If such a system is left for a certain period of time, the bonding of the two particles will take place in order to decrease the total surface area, even though the temperature is lower than the melting point. This phenomenon of bonding of two or more particles with the application of heat only and at temperatures below melting point of any component of the system will be called sintering, although the powder metallurgists use this term in a broader sense, including the presence of molten phase and pressure. It is the objective of this paper to study this process and the mechanisms involved in it. This problem is of utmost importance to powder metallurgy and powder ceramics, and its technological aspects have been studied for a good many years. However, the powder metallurgical operations are too complex and include too many superimposing mechanisms, and too many variables for a direct study. It was therefore advisable for the purposes of this study to reduce the variables to a minimum. In this work the radius of the interface formed during bonding in a simple system composed of a spherical particle and a large block of the same metal was studied as a function of time and temperature. It is believed that the mechanism involved in this simple process is fundamental to any sintering operations. Previous Work J. Frenkell was the first to make a serious attempt to develop a theory of sintering. He assumed that the process consists of a slow deformation of crystalline particles under the influence of surface tension which reduces to a viscous flow where the coefficient of viscosity n is related to the self-diffusion coefficient D by the following equation 1 _ D D6kT [1] where 6 is interatomic distance, k the Boltzman constant, and T the absolute temperature. This type of viscous flow of a crystalline substance is essentially different from the ordinary plastic flow. The latter is a specific propcrty of crystals and cannot take place in amorphous bodies. According to Frenkel this viscous type of flow is due to the diffusion of the holes or vacancies arising in the lattice. He was able to derive an equation relating the growth of the interface between two spherical crystalline particles or between a particle and a semi-infinite crystal (Fig 1) to time t at constant temperature. This relationship can be written as follows: x²— 3/2 a/nt [2] where x is the radius of the interface assumed to be circular, a the original radius of the sphere and a surface tension of the material. The other assump- x tions are that x is less than 0.3 and that during the period 1 the original radius, a, of the metallic particle did not change appreciably. A. J. Shaler and J. Wulff2 followed closely the ideas of Frenkel in their theory of sintering of a mass of metallic powder. Neither Frenkel nor Shaler has validated his theoretical speculations with conclusive experimental data. Two measurements reported by

Jan 1, 1950

By Roger A. Gregg, Barry J. Piearcey

MANY of the nickel-base superalloys developed recently for use in the as-cast condition exhibit a massive "white-etching" constituent1 in the inter-dendritic regions. Commercial alloys in this category are SM 200,* IN 100, INCO 713, and Nicrotung. The appearance of a similar microconstituent in nickel-rich Ni-A1-B alloys has been reported by Schijbel and Stadelmaier. Their investigation revealed that this constituent was the binary eutectic of the terminal nickel-base solid solution and the inter metallic based on Ni3A1. This binary eutectic is degenerate and NhA1 is the major phase. At lower temperatures the eutectic composition lies within the NkA1 phase field and under equilibrium conditions is single-phase NisAl. Taylor and F&apos;loyd3 have shown that in Ni-Al-Cr alloys containing at least 8 at. pct Cr, liquid compositions which solidify by the eutectic reaction in the nickel-rich portion, precipitate nickel-base solid solution and NiAl rather than nickel-base solid solution and NkA1 in the binary Ni-A1 system. Since the nickel-base alloys contain chromium in excess of 8 at. pct and are further alloyed with one or more of the elements titanium, cobalt, molybdenum, or tungsten, it is possible that the eutectic could contain NiAl rather than NisAl. In addition, Benson4 has reported that in low-nickel austenitic high-temperature alloys, which possess Ni/(Al + Ti) atomic-weight ratios <18.0, the Ni (Al, Ti) phase may precipitate from the melt during solidification. Since SM 200 and similar high-temperature materials were developed from alloys which were designed for solution treatment, the appearance of a eutectic would indicate that the limit of solid solubility has been exceeded. The purpose of this note is to confirm that the massive white constituent in the complex nickel-base alloys investigated is based on the binary eutectic Ni + NbAl and that the limit of solid solubility need not be exceeded to produce it, in common with other observations of cast alloys. Successive polishing of a sample of SM 200 showed that, in agreement with Schobel and Stadelmaier, particles of the constituent were spherulitic and in particular were a) situated between cored dendrite arms, Fig. 1, and b) nucleated at the surface of dendrites, Fig. 2. The Ni/(Al + Ti) atomic-weight ratios for the nickel-base alloys which were observed to contain the massive eutectic constituent in the interdendritic regions are 12.1 (Nicrotung), 9.2 (IN loo), 19.5 (INCO 713), and 14.5 (SM 200). However, the results of X-ray analysis of these alloys in the as-cast condition failed to reveal the presence of the Ni (Al, Ti) phase. An electron microanalyzer was therefore employed to analyze the composition of this constituent in SM 200. The results of analyses of representative particles are as follows5: 8.4 at. pct Ti, 8.8 at. pct Co, 5.5 at. pct Cr, 0.9 at. pct W, 12.8 at. pct Al, and 63.6 at. pct Ni. Assuming that

Jan 1, 1964

By John M. Kelly

New Mexico produced 38,882,342 bbl. of oil in 1943, and regained seventh place among the oil-producing states. This production was an increase of 6,968,526 bbl., or 21.8 per cent, over the figure for 1942. The maximum per-well allowable on Jan. I, 1943, was 38 bbl. daily and at the end of the year this figure had been increased to 48 bbl. Allocations as set by the New Mexico Oil Conservation Commission closely followed recommendations by the Petroleum Administrator for War and the average daily pipe-line runs were 106,476 bbl., being within 2.2 per cent of these allocations. Production for Lea County was 33,043,925 bbl.; Eddy County, 5,405,-967 bbl.; northwestern New Mexico, 432,070 bbl., and Chaves County, 380 barrels. Drilling activity for New Mexico in 1943 was only 75 per cent of that in 1942, with 255 completions. Of these completions 180 were oil wells, 10 gas wells and 65 dry holes. The ratio of dry holes to producers, more than I to 3, was the greatest in recent years. Of these dry holes, 46 were drilled within the boundaries of proven . areas while 19 were wildcats. Wildcat drilling during 1943 was responsible for the discovery of four new oil fields and one new gas field, as well as three extensions to existing proration areas. At the close of the year the New Mexico Oil Conservation Commission had designated 64 areas as proven for oil and/or gas. The Monument area was again New Mexico&apos;s largest producing oil field, with an annual production of 7,228,855 bbl. Next was Eunice, with 6,461,044 bbl., followed by Vacuum with 4,946,110 bbl. IIobbs, ranking fourth, with 3,799,114 bbl., was the leader in total recovery with an accumulated production of 104,180,53I bbl., or more than 10,000 bbl. per acre to date. Drilling activity in Lea County accounted for completion of 67 oil wells, 2 gas wells and 24 dry holes. One of these oil wells was the discovery well of a new area and three extended proven areas. The most active drilling campaign in the county was again in the Maljamar area, where 18 oil wells were completed. The Maljamar Cooperative Repressuring Agreement affected 141 producing wells, and operations were a decided success, more than 85 per cent of the gas produced being returned to formation. The new oil field for Lea County was designated as the San Simon area although boundaries have not been established to date. Discovery well for this area was the Skelly Oil Company&apos;s State U. No. I, in theNE. NE. K of sec. 5, T.22 S.,R.ssE. This well was drilled to a total depth of 4183 ft. and plugged back to 4138 ft. after encountering bottom-hole water. Initial production was 124 bbl. per day on the pump. This oil is 37.4&apos; gravity and has a sulphur content of I per cent. Productian is from Yates sand of Permian age. The Lynn area of southern Lea cbunty was extended 145 miles to the northwest

Jan 1, 1944

By John M. Kelly

New Mexico produced 38,882,342 bbl. of oil in 1943, and regained seventh place among the oil-producing states. This production was an increase of 6,968,526 bbl., or 21.8 per cent, over the figure for 1942. The maximum per-well allowable on Jan. I, 1943, was 38 bbl. daily and at the end of the year this figure had been increased to 48 bbl. Allocations as set by the New Mexico Oil Conservation Commission closely followed recommendations by the Petroleum Administrator for War and the average daily pipe-line runs were 106,476 bbl., being within 2.2 per cent of these allocations. Production for Lea County was 33,043,925 bbl.; Eddy County, 5,405,-967 bbl.; northwestern New Mexico, 432,070 bbl., and Chaves County, 380 barrels. Drilling activity for New Mexico in 1943 was only 75 per cent of that in 1942, with 255 completions. Of these completions 180 were oil wells, 10 gas wells and 65 dry holes. The ratio of dry holes to producers, more than I to 3, was the greatest in recent years. Of these dry holes, 46 were drilled within the boundaries of proven . areas while 19 were wildcats. Wildcat drilling during 1943 was responsible for the discovery of four new oil fields and one new gas field, as well as three extensions to existing proration areas. At the close of the year the New Mexico Oil Conservation Commission had designated 64 areas as proven for oil and/or gas. The Monument area was again New Mexico&apos;s largest producing oil field, with an annual production of 7,228,855 bbl. Next was Eunice, with 6,461,044 bbl., followed by Vacuum with 4,946,110 bbl. IIobbs, ranking fourth, with 3,799,114 bbl., was the leader in total recovery with an accumulated production of 104,180,53I bbl., or more than 10,000 bbl. per acre to date. Drilling activity in Lea County accounted for completion of 67 oil wells, 2 gas wells and 24 dry holes. One of these oil wells was the discovery well of a new area and three extended proven areas. The most active drilling campaign in the county was again in the Maljamar area, where 18 oil wells were completed. The Maljamar Cooperative Repressuring Agreement affected 141 producing wells, and operations were a decided success, more than 85 per cent of the gas produced being returned to formation. The new oil field for Lea County was designated as the San Simon area although boundaries have not been established to date. Discovery well for this area was the Skelly Oil Company&apos;s State U. No. I, in theNE. NE. K of sec. 5, T.22 S.,R.ssE. This well was drilled to a total depth of 4183 ft. and plugged back to 4138 ft. after encountering bottom-hole water. Initial production was 124 bbl. per day on the pump. This oil is 37.4&apos; gravity and has a sulphur content of I per cent. Productian is from Yates sand of Permian age. The Lynn area of southern Lea cbunty was extended 145 miles to the northwest

Jan 1, 1944

By A. Andreas

New Mexico established an annual record by producing 38,897,741 bbl. of oil during 1940. This was approximately 6 per cent greater than the 1939 production of 36,746,840 bbl. The daily average produc-tion was 106,569 bbl. New Mexico retained its position as the seventh oil-producing state. The recommendations of the United States Bureau of Mines were followed by the Oil Conservation Commission in setting the monthly state allowable. At the beginning of the year the average top allowable for each qc-acre unit was 40 bbl. and at the close of the year it was 36 bbl. Remedial work by the operators has been extremely beneficial and satisfactory in reducing the gas-oil ratios in various fields. Gas formerly blown into the air is now being processed by numerous casinghead plants. The Oil Conservation Commission, with the full cooperation of the Proration Office and operators, has taken bottom-hole pressure surveys and has done considerable remedial work in various fields. Two new oil fields and one gas field were discovered in New Mexico during 1940. Numerous extensions to the existing fields were made. Some of these were definitely wildcats in the same townships designated as fields and some, although called extensions, were more than 3 miles from production. Lea County continued to be the largest oil-producing county in the state, with a production of 33,976,394 bbl. It had the largest number of completions during 1940, with 303 oil wells, 9 gas wells and 13 dry holes—a total of 325 wells. Eddy County was the next most active county, with 239 completions, of which 163 were oil wells, 8 gas wells and 68 dry holes. It produced 4,405,158 bbl. of oil during the year. The increased activity in Eddy County and the completion of a large number of producing oil wells have created a transportation problem that can be solved only by additional pipe-line facilities. During the year Eddy County was unable to produce 1,500,000 bbl. of its allowable oil, because there was no pipe-line outlet. There were 601 wells completed in New Mexico in 1940, of which 478 were oil wells, 22 gas wells and IOI dry holes. This was a decline of approximately 9.5 per cent in the number of completions compared with 1939, when 659 wells were drilled. Southeastern New Mexico Lea County.—The largest producing field in Lea County was the Monument field, with 6,894,475 bbl.; followed by Eunice with 6,559,348 bbl. and Vacuum with 4,743,065 bbl. The Hobbs pool, which for years was the largest producing field in the state of New Mexico, was fourth with 3,790,477 bbl. The Vacuum pool was the most active area, having 68 completions, of which 67 were oil wells and one was a dry hole. Only one new field was discovered in Lea County during 1940; the discovery well was in the Caprock area, the Livermore State No. I, in the SE. 1/4 SE. 1/4 sec. 30, T. 12 S, R. 32 E. This well was drilled to a

Jan 1, 1941

By A. Andreas

New Mexico established an annual record by producing 38,897,741 bbl. of oil during 1940. This was approximately 6 per cent greater than the 1939 production of 36,746,840 bbl. The daily average produc-tion was 106,569 bbl. New Mexico retained its position as the seventh oil-producing state. The recommendations of the United States Bureau of Mines were followed by the Oil Conservation Commission in setting the monthly state allowable. At the beginning of the year the average top allowable for each qc-acre unit was 40 bbl. and at the close of the year it was 36 bbl. Remedial work by the operators has been extremely beneficial and satisfactory in reducing the gas-oil ratios in various fields. Gas formerly blown into the air is now being processed by numerous casinghead plants. The Oil Conservation Commission, with the full cooperation of the Proration Office and operators, has taken bottom-hole pressure surveys and has done considerable remedial work in various fields. Two new oil fields and one gas field were discovered in New Mexico during 1940. Numerous extensions to the existing fields were made. Some of these were definitely wildcats in the same townships designated as fields and some, although called extensions, were more than 3 miles from production. Lea County continued to be the largest oil-producing county in the state, with a production of 33,976,394 bbl. It had the largest number of completions during 1940, with 303 oil wells, 9 gas wells and 13 dry holes—a total of 325 wells. Eddy County was the next most active county, with 239 completions, of which 163 were oil wells, 8 gas wells and 68 dry holes. It produced 4,405,158 bbl. of oil during the year. The increased activity in Eddy County and the completion of a large number of producing oil wells have created a transportation problem that can be solved only by additional pipe-line facilities. During the year Eddy County was unable to produce 1,500,000 bbl. of its allowable oil, because there was no pipe-line outlet. There were 601 wells completed in New Mexico in 1940, of which 478 were oil wells, 22 gas wells and IOI dry holes. This was a decline of approximately 9.5 per cent in the number of completions compared with 1939, when 659 wells were drilled. Southeastern New Mexico Lea County.—The largest producing field in Lea County was the Monument field, with 6,894,475 bbl.; followed by Eunice with 6,559,348 bbl. and Vacuum with 4,743,065 bbl. The Hobbs pool, which for years was the largest producing field in the state of New Mexico, was fourth with 3,790,477 bbl. The Vacuum pool was the most active area, having 68 completions, of which 67 were oil wells and one was a dry hole. Only one new field was discovered in Lea County during 1940; the discovery well was in the Caprock area, the Livermore State No. I, in the SE. 1/4 SE. 1/4 sec. 30, T. 12 S, R. 32 E. This well was drilled to a

Jan 1, 1941

By Floyd C. Kelly

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

Jan 1, 1929

By Floyd C. Kelly

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

Jan 1, 1929

By S. I. Liu

THE effects of strain histories, consisting of several prestrains in opposite directions, on the flow and fracturing characteristics of metals determined in a final test have been investigated previously.&apos;" Such strain histories vary from a single prestrain in tension or compression to the number of strain cycles leading to fatigue failure.&apos; Between these two limits, various strain histories could be visualized and some can be attained readily. One such example is a strain history consisting of a first prestrain in tension of various magnitudes and a second prestrain in compression also of various mag-nitude. In this investigation the strain history was extended to the combination of these two limits, i.e., a single prestrain in tension or compression followed by balanced strain cycles of a selected magnitude e, = k0.12. It was found in this case that only compressive initial prestrains could be investigated with sufficient accuracy.* Such strain histories can be considered also as (low cycle) fatigue tests of a metal subjected to various amounts of cold working. It appears from previous publications that cold working within a wide range of reductions usually raises the un-notched fatigue strength of many metals.&apos;-&apos; This effect, however, has been found to be inconsistent and sometimes reversed for other metals?.7 Furthermore, Ludwik reports that the yield strength of cold-worked specimens may be reduced by cyclic strains, while that of materials without cold work is generally increased in the initial cycles." " In addition to the above tests, a study was made of the effect of intermediate re-solution heat treatment on low cycle fatigue behavior. Such anneals should eliminate the strain hardening induced by the cyclic strains. As far as their effect on the fracture characteristics is concerned, a few previous tests seemed to indicate that the damage resulting from cyclic strains is retained only partially after heat treatment." A further investigation was made in which one specimen was subjected to repeated unbalanced tension cycles in which the strain interval was approximately $ 0.013. This repetition of plastic tension damages the material slightly. This result appears to confirm Ludwik&apos;s observations." " Commercial 3/4-in. rod of the aluminum alloy 24ST4 was selected for this investigation. The material was subjected to the following treatments before machining: 1—Re-solution treatment at 920" ± 10°F for 45 min, 2—water quench at room temperature, and 3—aging for four days at room tem-perature.? The treated material then was machined to desired specimen contour and tested. A coolant was used during machining to minimize any artificial aging effects of heating during machining. In some cases the 24ST4 specimens were reheat treated after having been strained. In these cases, the heat treatment was the same as the re-solution heat treatment described above. Procedure As shown in Fig. 1, threaded end specimens with a minimum diameter of 0.266 in. and a contour radius of 2 in. were used for prestraining to an axial compressive strain ranging from 6, = —0.10 to E, = —0.48. For large prestrains, two consecutive corn-

Jan 1, 1952