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By Bahrein Petroleum Company

In Comodoro Rivadavia, well 8. 132, drilled in zone No. 2, has discovered between 5205 and 5297 ft., the dcepest pool yct found in this field. The oil production in Bahrein for the year 1939 totaled 7,588,554 bbl., a decline of 709,444 bbl. from the 1939 production of 8,297,998 bbl. The production for the first seven months of 1939 remained fairly constant, the daily average by months during this period ranging between 20,000 and 22,000 bbl. per day. The daily average rose in August to the year's high of 23,800 bbl. per day, then dropped gradually to the year's low of 18,787 bbl. per day for November. The daily average for the year was 20,791 bbl. At the end of 1939 there were 59 wells producing and 8 wells drilling.

Jan 1, 1940

By Bahrein Petroleum Company

In Comodoro Rivadavia, well 8. 132, drilled in zone No. 2, has discovered between 5205 and 5297 ft., the dcepest pool yct found in this field. The oil production in Bahrein for the year 1939 totaled 7,588,554 bbl., a decline of 709,444 bbl. from the 1939 production of 8,297,998 bbl. The production for the first seven months of 1939 remained fairly constant, the daily average by months during this period ranging between 20,000 and 22,000 bbl. per day. The daily average rose in August to the year's high of 23,800 bbl. per day, then dropped gradually to the year's low of 18,787 bbl. per day for November. The daily average for the year was 20,791 bbl. At the end of 1939 there were 59 wells producing and 8 wells drilling.

Jan 1, 1940

By Howard R. Hume, Terry R. West, William R. Judd

One of the outcomes of a sector slope design in a large open pit in the western United States has been the scrutiny of the structural domain concept. These domains essentially define the area of influence of particular structural characteristics. In the present instance these structural characteristics are joint discontinuities. One of the major drawbacks of defining a domain is that unless large quantities of discontinuity data are available this process of definition is largely qualitative in nature. Viewed from a discontinuity analysis aspect the orientations of all the major joint sets at a given point are a concise descriptor of the structural geologic regime at that location. This is important to domain boundary definition, this in turn is extremely important for assigning which joint sets to use as input for slope stability analysis in a given discontinuity domain. An attempt has been made to develop a quantitative method for defining these discontinuity domains based on limited amounts of orientation data thereby reducing the subjectivity normally involved in such operations. Subjectivity is not always a problem if large quantities of joint orientation data are available, since the mean and variance of joint clusters always can be compared and then grouped to define these domains. However, even this method suffers from the problem that only a single joint set orientation can be considered at a time during the grouping process. On the other hand a discontinuity domain requires that all joint sets at a point be considered simultaneously to truly define the structural discontinuity character of that point. This provides a far more complete

Jan 1, 1982

By William P. Blake

The metallic element Nickel, discovered by Cronstedt the mineralogist, in the year 1751, as a peculiar metal in kupfer-nickel, remained for a long time comparatively unknown in its true charac-

Jan 1, 1883

By C. F. Knutson, Martin Felsenthal, J. D. Lung, J. D. Sudbury

This paper has been written to summarize the laboratory and field studies leading to injection of Pacific Ocean water into the Third Grubb formation. Laboratory tests for studying the permeabilities of cores to Pacific Ocean water are described. Resu1ts of these tests showed that the water could be successfully injected if it is chertzically stable, sterile, and properly filtered. Clay swelling was shown to be a comparatively minor factor in permeability reduction. Studies leading to development of an economical system for properly conditioning the ocean water are discussed. It was necessary to control pH, calcium carbonate deposition, bacterial growth, iron solubility. oxygen, and suspended .solids. A relatively simple system combining the use of sulifur dioxide, a quaternary rlmmonium chloride, and filtration was shown to adeqrrately control all these factors. This combination has not previozrsly been used as a water treating technique. Evaluation tests of the water conditioning system prior to injection are described, and results of such tests are presented. Control measures needed to insure a continusously adequate water treatment are reviewed. INTRODUCTION The utilization of sea water for waterflooding has only recently been attempted. Knowledge of treating requirements has been limited, and in most cases no water treating has been done. Prior to the initiation of the Third Grubb zone pilot water flood at Ventura, Calif.,1,2 extensive laboratory research was done in an effort to define the treatment necessary to provide a suitable injection fluid. Close coordination and cooperation between field and research personnel were found to be the foremost requisites in developing the most economical and practical method for treating ocean water. LABORATORY STUDIES Plugging Tendencies of Untreated Ocean Water A program of laboratory studies was initiated for the purpose of evaluating whether ocean water could be injected into the formation for prolonged periods of time without causing plugging of the pore spaces of the formation. Because of the fairly low permeability of the formation (averaging about 40 md), it was realized from the outset that a water of exceptionally high quality was needed. Ocean water used in the laboratory studies was carefully filtered through ultrafine fritted glass filters, having nominal maximum pore sizes of 1.4 microns. Permeability tests were then performed on representative core material from the formation. It soon became apparent in these tests that filtration alone was not a sufficient treatment for the ocean water. Prolonged injection of the filtered water caused rapid plugging of the core samples. The permeability decline of a typical sample is illustrated by Curve A in Fig. 1. The several factors which can contribute to this plugging tendency are briefly reviewed below: Interaction with Formation Clays An evaluation of clay swelling effects on liquid permeability was made using core samples from the Grubb formation. An oil was chosen for determining the reference liquid permeability because it would not tend to react with any clays that might be present in the formation. The samples were then extracted, dried, and resat-urated with either treated ocean water, formation water, or fresh water. Permeabilities to the various waters were then determined. Results of this test series are summarized in Fig. 7. The difference between the oil permeability and water

Jan 1, 1957

By Walter von der Linden

A description is presented of the mining conditions of four longwall shield type support installations in the Pittsburgh seam in northern West Virginia and southwestern Pennsylvania. Details of roof control and operating procedures, production and performance data, and equipment description and basic engineering specifications are given for these four longwall installations. The range of mining heights was between 150 and 250 cm (60 and 95 in.). The major accomplishment of the shield supports in all four faces was the provision of an almost 100% availability for coal cutting; i.e., the face-down time due to roof control problems and support maintenance requirements was minimal.

Jan 1, 1978

By Geo. H. Ashley

The following paper is intended to be suggestive only, and to open the way for discussion and further observation. Its preparation was requested only two days before the time limit set for the submission of the papers comprising this symposium. Thus no time existed for detailed studies, so it is largely a memorandum of such facts as have come incidentally to the notice of the writer in the study of coal in the field. The field study of sulfur in coal has received very little special attention or description from coal student's. The presence of sulfur concretions is noted in hundreds of descriptions, and certain benches of a coal bed may be described as "sulfury" or the presence and position of sulfur bands may be noted in coal sections in connection with sampling. It may be accepted that some sulfur is present in all coal. The amount varies greatly in different regions, in different beds, and in the same bed in different areas. The anthracite of Rhode Island comes the nearest of any coal known to the writer of being free from sulfur, several analyses of that coal showing less than 0.1 per cent. Subbitumi-nous coals in Colorado in a few places have close to 0.2 per cent. of sulfur on the dry-coal basis and in other states subbituminous coals approach this lower limit. Bituminous coals seldom run under 0.4 per cent. of sulfur on the dry basis, though in a few places dry bituminous coals in Colorado and Washington have between 0.3 and 0.4 per cent. The better known bituminous coals have almost everywhere over 0.4 per cent. The best of the Pocahontas and New River coals run close to 0.4 per cent., but there is very little commercial coal in Pennsylvania, Ohio, Indiana, Illinois, Kentucky, or the other states, that runs under 0.5 per cent. on the dry basis. From these minimum figures, the amount will range up to 5 or 6 per cent. or higher if visible sulfur is not excluded. It must be remembered that the usual analysis of a coal bed is not intended to give the total proportion of sulfur in the bed but the amount in the coal after the removal of the more obvious and larger sulfur masses. Professor Parr has already pointed out that, chemically, sulfur occurs in several forms: as pyrite, organic sulfur, sulfates, and possibly as un-combined sulfur. Sulfur in the form of sulfates is commonly the obvious result of the weathering of pyrite and may be found in the coal within .

Jan 1, 1920

By James A. Burns

The challenge to designers of bulk materials handling systems is to apply the existing technology in areas where it has not been used and to foster better, cheaper and safer job performance. The Dashaveyor Co., a subsidiary of The Bendix Corp., built and tested a pilot system at Copper Range's White Pine mine. Based upon this success, a prototype system development was begun in 1967 to test the concepts in a full-scale, realistic environment.

Jan 11, 1973

By Leonard Larson

DURING several years immediately preceding the adoption of wet-charge smelting at McGill, various necessary conditions affecting this procedure, such as plant rearrangement and the metallurgical nature of the concentrate produced at the concentrator, were fully considered. Wet-charge smelting is not altogether novel to the recently recon-structed smelter at McGill. A number of years prior to this improve-ment, when flotation methods were initiated at the concentrator, large tonnages of wet and (at that time) sticky flotation concentrate were charged directly into the reverberatory furnaces, because of the difficulty in handling the entire tonnage in the roasters. The plant had excess reverberatory units and this surplus furnace capacity was utilized to smelt raw flotation concentrate. During the years 1927 and 1928, a number of actual operating furnace test runs were made to determine in principle the feasibility of wet-smelt-ing operation. Results were encouraging, and in November 1932 the roasting plant was shut clown. For some time thereafter the wet feed was delivered directly to the reverberatory side-charging calcine hoppers already in place. Feeding the wet material through the old calcine hoppers and charge holes into the furnace involved considerable labor, but under the conditions existing at that time it was desirable to continue wet smelting even under the handicap of this laborious procedure. The smelting plant during this period was on a curtailed production basis, operating only about 15 days per month. The alternate starting up and shutting clown of the roasting plant presented a difficult problem and charging the wet material directly to the furnace entirely eliminated this difficulty. The roasting plant was never operated thereafter.

Jan 1, 1938

The passing of Benjamin Bowden Lawrence in January, 1921, was a distinct loss to the engineering profession. Mr. Lawrence had a genius for reviving abandoned mines and developing them into substantial producers. A notable example of his work in this line was the Dives-Pelican near Georgetown, Colo. While on an exploring expedition in 1888, he examined this old mine and was convinced that bonanza ore still existed there. He located the owners of the property, and induced them to place sufficient capital at his disposal to enable him to re-open and explore this mine. So confident was he of the outcome that he undertook this work on a profit-sharing basis without salary. Within eighteen months the old Dives-Pelican was operating profitably, and for the following ten years it paid very substantial dividends. The late Theodore N. Vail was one of the owners of this old mine, and many years later, at a dinner given to Mr. Lawrence by the Alumni of Columbia University, Mr. Vail told the story of the resuscitation of the Dives-Pelican by Mr. Lawrence, and declared that the dividends he himself had received provided a large part of the funds that made possible the realization of his dream of establishing the long-distance telephone in this country. The E1 Cobre mines at Santiago de Cuba also owed their renewed life to Mr. Lawrence. Under his management, these mines produced and shipped several million pounds of copper per year. He was for several years consulting engineer for the Kerr Lake and other silver mines in the Cobalt region; the Kerr Lake became famous as a silver producer. Mr. Lawrence spent more than twenty years of his life in the mining camps of the West. He was but twenty-one years of age, and only a few months out of college, when he was appointed manager of the great Chautauqua Lode (a silver mine) located on Glacier Mountain near Montezuma, Colo. Here, isolated in the mountains for several months each year by ice and snow, he worked for five years to make these mines Pay. He possessed unusual breadth of vision and human understanding; he had ''personality plus," and when he opened an office in New York City as consulting engineer he quickly rose to an enviable position in his profession. Young engineers worked with enthusiasm under his guidance. He carefully selected his men, discussed fully with them the plans and policies to be pursued, then left them free to accomplish results in their own way. This attitude developed individuality and resourceful-

Jan 1, 1922

The passing of Benjamin Bowden Lawrence in January, 1921, was a distinct loss to the engineering profession. Mr. Lawrence had a genius for reviving abandoned mines and developing them into substantial producers. A notable example of his work in this line was the Dives-Pelican near Georgetown, Colo. While on an exploring expedition in 1888, he examined this old mine and was convinced that bonanza ore still existed there. He located the owners of the property, and induced them to place sufficient capital at his disposal to enable him to re-open and explore this mine. So confident was he of the outcome that he undertook this work on a profit-sharing basis without salary. Within eighteen months the old Dives-Pelican was operating profitably, and for the following ten years it paid very substantial dividends. The late Theodore N. Vail was one of the owners of this old mine, and many years later, at a dinner given to Mr. Lawrence by the Alumni of Columbia University, Mr. Vail told the story of the resuscitation of the Dives-Pelican by Mr. Lawrence, and declared that the dividends he himself had received provided a large part of the funds that made possible the realization of his dream of establishing the long-distance telephone in this country. The E1 Cobre mines at Santiago de Cuba also owed their renewed life to Mr. Lawrence. Under his management, these mines produced and shipped several million pounds of copper per year. He was for several years consulting engineer for the Kerr Lake and other silver mines in the Cobalt region; the Kerr Lake became famous as a silver producer. Mr. Lawrence spent more than twenty years of his life in the mining camps of the West. He was but twenty-one years of age, and only a few months out of college, when he was appointed manager of the great Chautauqua Lode (a silver mine) located on Glacier Mountain near Montezuma, Colo. Here, isolated in the mountains for several months each year by ice and snow, he worked for five years to make these mines Pay. He possessed unusual breadth of vision and human understanding; he had ''personality plus," and when he opened an office in New York City as consulting engineer he quickly rose to an enviable position in his profession. Young engineers worked with enthusiasm under his guidance. He carefully selected his men, discussed fully with them the plans and policies to be pursued, then left them free to accomplish results in their own way. This attitude developed individuality and resourceful-

Jan 1, 1922

By Earl L. H. Sackett

This laboratory centrifuge is unique in its low cost and ease of construction, its particular adaptability to problems encountered in an ore dressing laboratory and its simplicity of operation. It will treat a sample of the size ordinarily used in a laboratory flotation test. The centrifuge was designed at the Baroid Sales Division of the National Lead Co., Malvern, Ark., and built in a local machine shop to serve as a laboratory machine which would produce results comparable with those obtained in the large scale centrifugal deslimers in use in our Magnet Cove mill. The apparatus has served quite well in this capacity and has also proved effective as a deslimer on a variety of ore dressing problems. The cost of making this machine was relatively low and it is simple to operate. It is strictly a batch machine, but when operated under proper conditions, gives results which agree quite closely with large continuous-flow machines of the same type. Effective separation of minus 5 and 10 micron material is made in an undispersed pulp in a short time.

Jan 4, 1950

By E. Ryba, D. J. Michel

SAMPLES of REZn2 (RE = rare earth) intermetallic compounds prepared by a variety of techniques have been shown to exhibit an extensively twinned micro-structure.1-4 We have recently conducted compression tests at room temperature on specimens of HoZn2 prepared by a powder metallurgy technique.' The microstructures of specimens before and after testing are shown in Fig. 1. The "before" specimen, Fig. l(a), shows the basic twin structure of this material. Fig. l(b) shows the microstructure of the "after" specimen just below the fracture surface and reveals considerable cross-twinning as well as additional

Jan 1, 1970

By Waldemar Lindgren

I. INTRODUCTION AT the time of the discovery of America the old world had a scant supply-of the precious metals. Both the northern and the southern part of the new continent proved wonderfully rich in gold and silver and its treasures were eagerly looted; though the looting has lasted four centuries, the nines of its mountain chains are far from being exhausted. Even the later discoveries in Australasia and eastern Siberia could not rob the Western Hemisphere of its position as the greatest gold and silver producing region of the world, though finally the developments in a narrow and circumscribed area in South Africa wrested from the Americas their supremacy in the production of gold. Nevertheless the history of the two parts of the great western continent has been strikingly different. At first the Spaniards extracted vast treasures of silver from Mexico, Peru, and Bolivia, while Colombia and some placer deposits in Peru yielded a smaller quantity of gold. A couple of centuries later, a stream of gold began to flow from Brazil, the silver production from the countries mentioned above continuing strong in the meanwhile. Later on, the yield of South America diminished, but to offset this there began a wonderful series of discoveries in North America. The gold fields of California astonished the world; and when the cream of these had been skimmed off there began a no less amazing development of the Central Cordilleran gold and silver districts, which soon wade the United States the greatest producer of the precious metals. Aided by ever improving technique, extensive exploration, and a system of railroads, the yield was maintained and increased. Still later followed the discoveries of the gold fields of the arctic region and silenced those who had maintained that the zenith in gold production had passed. Recently the province of Ontario in eastern Canada

Jan 4, 1916

By Irwin Roman

In addition to projects such as those reported in parts I and II above, the Section of Geo-physics of the Federal Government has undertaken a considerable amount of fundamental research. Two such field-projects may be mentioned, one a magnetometric study in the Comstock Dis-trict of Nevada, and the other a resistivity-study of snow and ice. In addition to the field-problems, there have been two classes of research of a mathematical type. One of these has been the preparation of tables, scales, and charts for the important geophysical functions already known; the other has been the extension of the relations involved in the resistivity-problem. The magnetometric study at Spring Valley, in the Comstock District, was made for the pur-pose of determining the value of the magnetometer in extending the knowledge of a region, as ob-tained by purely geological means. The variations in the vertical magnetic intensity were mea-sured with an Askania balance at intervals of 20 feet, along lines as shown in Figure I.. These lines were 100 or 500 feet apart over an area approximately a rectangle 6000 by 7500 feet. In addition to the lines shown, two areas were selected for more intensive study. In one, short

Jan 1, 1940

By Chas. A. Ashburner

The occurrence of oil- and gas-springs in the State of New York has been a fact of historical record since 1627, when the existence of the Cuba oil-spring was first recorded. The utilization of natural gas at Fredonia in 1821 attracted the attention of the public to the possibility of obtaining an illuminating gas by digging and drilling into the rocks. No active search was made, however, for oil or gas by the drilling of wells until after the discovery of commercial oil in Pennsylvania in 1859. In 1862 a well was drilled at Bradford, McKean County, Pennsylvania, but a few miles south of the New York state line, to the depth of 200 feet, in search of the oil-sand which had been found at Titusville, Oil City, and at other points in Western Pennsylvania. Immediately subsequent to this, other wells were drilled in search

Jan 1, 1888

By S. G. Bankoff

INCE1 proposed that electrostatic attraction between oppositely charged particles was responsible for slime-coating. Del Giudice2 postulated the metathetic formation of a cementing compound. Wark3 suggested that prevention of slime-coating was related to peptization of the slime. [ ] In the experiments of Table I the technique employed was essentially that of del Giudice, with the difference that the particle was examined under a film of water rather than dry.4 In general, the polished particle was agitated for 2 min. in a pulp consisting of 12.5 grams of the slime (-200 mesh) and 50 c.c. of distilled water, washed in three baths of distilled water, and examined at 220 diameters with the Leitz Ultropak. Observations of Brownian movement were made at 850 diameters with dark-field illumination. Several of these experiments do not jibe with the metathesis theory. According to published solubilities,5,6 the lead salts of the anions in experiments [c] through g are more insoluble than lead carbonate, therefore should prevent the formation of lead carbonate on the galena surface. In experiment [i] the calcium oxalate, which presumably was on the calcite surfaces, should have permitted the formation of a lead carbonate cement by virtue of its greater solubility. Experiments [j] through m show that the addition of lime accelerates the deposition of quartz onto a galena surface. The writer is unable to postulate a satisfactory cementing compound, according to the metathesis theory, to explain this effect. These experiments led to the conclusion that the metathetic formation of a cement-

Jan 1, 1941

By C. O. Brawner

Simple, specific rules for achieving slope stability in open-pit mines are impossible to devise. Each pit has a different mining program and a different set of environmental conditions, and its final slope design must be based on an individual evaluation of the actual site. The overall philosophy of pit stability, however, is tending towards a limit design concept. Since slope angle has a great influence on the economics of most open-pit mines, efforts are being made to reduce the theoretical factor of safety for slope stability to very near 1.0. (Factor of safety is here defined as shear strength/shear stress on the most probable plane of failure.) Actually, where detailed, statistically significant testing has been done and a comprehensive ground control program is being instituted to warn of movement at an early stage, safety factors as low as 1.1 or 1.2 may be justified. The cost of the necessary procedures, however, is high. There are many factors that influence stability, but this article will be confined to three-rock structure, groundwater, and blasting.

Jan 8, 1969

By Harold Markus, Gerhard Derge

THE first paper1 of this series described a technique of careful surface preparation by means of which reproducible results may be obtained from potential measurements of the behavior of tin in carbonate solutions with a pH range from 8.4 to 11.2. It then went on to establish the behavior of pure tin electrodes under these conditions and showed that the metal remains active at all times, though the steady potential attained after several hours decreases from I.I2[t] volts at a pH of 12.6 to 0.6 volts at a pH of 8.4. This behavior may serve as a norm with which all other data can be compared. In the second paper,2 small amounts of other anions were added to the carbonate solutions and the conclusion was reached that the common impurities encountered in alkaline materials packaged in tin do not increase corrosion. In fact, in some cases these anions may actually promote the formation of protective films. The present paper rounds out this survey by presenting data on the influence of cations added to the carbonate solutions, as well as the effect of alloy additions to the tin. In many cases the potential data are supplemented with weight-loss measurements. Information is also presented on the effects of some additional anions, the influence of gases above the electrolyte, the behavior of high-purity tin, and the effect of atmospheric oxidation on the corrosion resistance of the above-named alloys. Analysis of the entire body of data discloses some general rules applicable to corrosion in carbonate solutions. The experimental methods used are the same as those previously described. EXPERIMENTAL DATA Cations.-The carbonates of the cations K+, Li+, NH4+, which are soluble, were studied in the same way as the anions, by adding 0.01 mol of the metal carbonate to one liter of 0.2 M sodium carbonate solution, pH 11.2, or to 0.1 M sodium bicarbonate, pH 8.4. The other metallic carbonates are only slightly soluble, of the order of 0 7-3 mols per liter or less, and the sodium carbonate solutions were saturated by adding excess reagent several days before the experiment, shaking frequently, and filtering just before use. The chemicals were c.p. grade in each case except the indium salt. This salt was prepared by solution of the metal in hydrochloric acid and precipitation by addition of Na2CO3. These cations may be divided into two classes, according to their effect on the potential behavior of the tin: (I) normal, (2) passive. To offer a basis of comparison, curves I of Figs. I and 2 are given to illustrate the behavior of tin in carbonate solutions saturated with CaCO3. These curves are the

Jan 1, 1941

By F. H. Froes, D. H. Warrington

Electron microscope evidence which indicates that TaC may precipitate at random sites in the matrix is presented. Initially the particles are almost spherical and coherent with the matrix. However, as they grow in conditions in which there are insufficient vacancies to relieve lattice strain, the particles rapidly lose coherency in two directions and continue to grow as plates with approximately the full lattice mismatch strain present perpendicular to the plane of the plate. The necessary relief of strain comes from dislocations loops which do not become visible until the later stages of aging. The rapid decrease of apparent strain to low values of appoximately 1 pct at small particle sizes arises not from a complete incoherency but from applying a model wrong for the particle shape and strain distribution. PREVIOUS work has shown that MC-type carbides may precipitate intragranularly in austenitic stainless steel on dislocations,1&apos;2 in association with stacking faults,3&apos;4 and randomly through the matrix,5-7 In investigations of the matrix precipitate by thin-foil electron microscopy, considerable lattice strain has been found to occur around the precipitating phase.7&apos;8 Attempts have been made to evaluate the amount of lattice strain by using the methods developed by Ashby and brown.9,10 Values of the linear strain, much less than the 17 pct theoretical mismatch (for TaC), have been reported; it has been suggested that this is due to either a loss of coherency1&apos; or vacancy absorption which occurs during either the initial nucleation or growth of the precipitate." This report is an extension of earlier work7 that dealt with the precipitation of TaC from an 18Cr/12Ni/ 2Ta/O.lC alloy after it had been quenched from 1300°C and aged between 600" and 840°C. In particular, the shape of the precipitate particles and the amount of strain in the matrix, due to the precipitate, have been studied. The work described here is part of a wider investigation of factors that affect carbide precipitation in austenitic stainless steel," details of which are to appear elsewhere. RESULTS The present investigation can be conveniently split into two aspects of the strain-fields surrounding the matrix particles: 1) information derived from the strain-field which indicates the shape and habit plane of the precipitate particles and 2) the magnitude and sign of the strain-field. The Shape and Habit Plane of the TaC Precipitate. In the early stages of aging twin lobes (normally black F. H. FROES, formerly at the University of Sheffield, Sheffield, England, is Staff Scientist, Colt Industries, Crucible Materials Research Center, Pittsburgh, Pa. D. H. WARRINGTON is Lecturer, Department of Metallurgy, University of Sheffield. Manuscript submitted November 1, 1968. IMD on white background, i.e., for the deviation parameter, S > 0) that indicate the strained region of the matrix define the position of the particles by bright field transmission electron microscopy. The actual particles were not detected until they were approximately 120Å diam; below this size they were too small to be imaged in the electron microscope. This meant that particle growth that had occurred before this stage had to be inferred from the matrix strain-field contrast. In all cases when diffraction effects were observed from the precipitate particles, a cube-cube orientation relationship (i.e., (llO)ppt Il<llO>matrix and {1ll }ppt {III} matrix) existed between the precipitate and the matrix. From the matrix precipitate particles lying along edge-on {111} planes (e.g., at A, Fig. I), the precipitates are seen to be plate-like with their diameter being roughly 18 times their thickness after 5000 hr at 650°C. However, the exact shape of the particles cannot be determined because of the masking effect of the strain-field contrast. If a dark-field micrograph, using a precipitate reflection, is studied, Fig. 2, a number of the projected images of the TaC particles [on the (110) foil surface] apear to have straight edges parallel to projected f111) planes. Thus, it appears that in the later stages of aging the TaC particles are plate-like with some tendency for the edges of the plate to be bounded by the matrix close-packed {ill} planes (though the general shape of the particles in the plane of the plate is circular and thus the "diameter" of the particles has a real physical significance). It should be noted that the bands of fine discrete particles observed in Figs. 1 and 2 are not the matrix precipitate discussed in this paper but are precipitates associated with extrinsic stacking faults3j4 occurring on (111) matrix planes. **£** ****** \ *x 23 Fig. 1—18/12/2~a/0.1~ alloy. Solution treated at 1300°C for 1 hr, water quenched, and aged 5000 hr at 650°C. The (112) directions shown are the traces of the e&e-on (111) planes. Foil normal [110]; operating reflection (331); bright field micrograph.

Jan 1, 1970