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By James J. Norton, Lincoln R. Page

Effective methods for determining grade and reserves of pegmatites in advance of mining have been developed in recent years. When intensive work began on the economic geology of pegmatites during the early years of World War II, it was widely believed that grade and reserves could be estimated only in a most general way. The literature indicated that not all pegmatite deposits are unpredictable, but statements emphasizing unpredictability and irregularity seem to have been more widely accepted. Many standard references reflect the prevailing opinion that minerals are unsystematic in their occurrence in pegmatites. Pegmatites have been de- scribed as "notorious for their irregular structure," and minerals within pegmatites as "irregularly distributed," "irregularly disseminated,'' of "erratic occurrence," "proverbially erratic in distribution," "characterized by extreme irregularity in size and distribution of the essential minerals, and variety and proportion of the accessory minerals, and "spotty."

Apr 1, 1956

By H. W. Imholz

Active interest in the North Central Texas area centered in the development of the Palo Pinto limestone-producing zone, near the town of Avoca, in the northeast part of Jones County. This producing horizon was discovered in 1937, in the Iron Mountain Oil Company's well No. 1 Olander, in sec. 196, B.B.B. & C. survey, at 3238 to 3250 ft. During the development of this pool, it was generally referred to as the Avoca pool. As a second pool has been discovered in the same producing zone, also near the town of Avoca, the writer has taken the liberty of changing the name of the original Avoca pool to Avoca-Olander pool. Forty producers had been drilled in the Avoca-Olander pool by the end of 1938; their initial ranged from 28 to 300 bbl. per hour. Stimulus was given to the interest in the development of the Palo Pinto limestone when the Ungren-Frazier No. 1 Griffin, in sec. 199, B.B.B. & C. survey, Jones County, found the limestone from 3225 to 3250 ft., with an initial production of 931 bbl. per day. (This new pool has been given the name of Avoca-Griffin pool, by the writer.) The best well to be completed, up to the present time, is the Bert Fields No. 1 Taylor in sec. 199, B.B.B. & C. survey, which had an initial production of 748 bbl. in 3 hours. The Owen-Snebold No. 1 McKeever in sec. 158, B.B.B. & C. survey, in northwest Shackelford County, added to the interest in the Palo Pinto limestone when it extended the Ivy pool with a well in the Palo Pinto limestone from 3145 to 3183 ft., and was estimated good for 6,000,000 cu. ft. of gas and 6000 bbl. of oil per day. During 1938, Stonewall County obtained its first commercial producer when the Stonewall Oil Co. in No. 1 Parriott discovered the Palo Pinto limestone saturated from 5169 to 5176 ft. and tested 371 bbl. per day. Two new producing horizons were discovered about 2 miles east of the old Noddle Creek pool, Jones County; the first, the Humble Oil & Refining Co. No. 1 Irvin, in sec. 48, block 18, T. & P. R. R. Co. survey, which had saturated limestone from 2550 to 2567 ft. and was good for 100 bbl. per day; the second, in the Humble No. 1 Horton, sec. 40, which

Jan 1, 1939

By H. W. Imholz

Active interest in the North Central Texas area centered in the development of the Palo Pinto limestone-producing zone, near the town of Avoca, in the northeast part of Jones County. This producing horizon was discovered in 1937, in the Iron Mountain Oil Company's well No. 1 Olander, in sec. 196, B.B.B. & C. survey, at 3238 to 3250 ft. During the development of this pool, it was generally referred to as the Avoca pool. As a second pool has been discovered in the same producing zone, also near the town of Avoca, the writer has taken the liberty of changing the name of the original Avoca pool to Avoca-Olander pool. Forty producers had been drilled in the Avoca-Olander pool by the end of 1938; their initial ranged from 28 to 300 bbl. per hour. Stimulus was given to the interest in the development of the Palo Pinto limestone when the Ungren-Frazier No. 1 Griffin, in sec. 199, B.B.B. & C. survey, Jones County, found the limestone from 3225 to 3250 ft., with an initial production of 931 bbl. per day. (This new pool has been given the name of Avoca-Griffin pool, by the writer.) The best well to be completed, up to the present time, is the Bert Fields No. 1 Taylor in sec. 199, B.B.B. & C. survey, which had an initial production of 748 bbl. in 3 hours. The Owen-Snebold No. 1 McKeever in sec. 158, B.B.B. & C. survey, in northwest Shackelford County, added to the interest in the Palo Pinto limestone when it extended the Ivy pool with a well in the Palo Pinto limestone from 3145 to 3183 ft., and was estimated good for 6,000,000 cu. ft. of gas and 6000 bbl. of oil per day. During 1938, Stonewall County obtained its first commercial producer when the Stonewall Oil Co. in No. 1 Parriott discovered the Palo Pinto limestone saturated from 5169 to 5176 ft. and tested 371 bbl. per day. Two new producing horizons were discovered about 2 miles east of the old Noddle Creek pool, Jones County; the first, the Humble Oil & Refining Co. No. 1 Irvin, in sec. 48, block 18, T. & P. R. R. Co. survey, which had saturated limestone from 2550 to 2567 ft. and was good for 100 bbl. per day; the second, in the Humble No. 1 Horton, sec. 40, which

Jan 1, 1939

By Robert Linton

AT its meeting on May 21, the Board of Directors approved the recommendations submitted by President Lovejoy and named a nominating committee for the year that is especially well distributed as to major technical interest and as to geography. As may be seen from the list published herewith, two come from the East, two from the Midwest, and three from the far West. Mr. Linton, the chairman, has been a valued member of the Institute for 36 years. A memorandum drawn up by Paul D. Merica, representing the A.I.M.E., and W. R. Barclay, representing The Institute of Metals of Great Britain, setting forth a reciprocal plan for special memberships in each Institute for members of the other, was discussed. Both societies already have formally approved the plan in principle and Dr. Merica was clothed with full authority to agree on a few small details that have not been settled, and conclude the arrangement in behalf of the Institute.

Jan 1, 1936

OUTSTANDING symbol of the machine age, the steam shovel needs no introduction. Few individuals there are, in the United States at least, that have not watched with fascination the almost human motion, the more than human strength, the rhythm of the whole steam-shovel cycle of crowding, digging, swinging, dumping, swinging, and crowding again. A mass of steel with some copper and other metals, fed with water and coal, guided by a single alert and dexterous operator, or perhaps two, does the work that would require 50 to 500 men or even more. The largest shovels working in the copper mines have loaded into waiting railway cars as much as 10,000 tons of ore in a single 8-hour shift. With no equipment but hand shovels, it would, in fact, be impossible to duplicate the work with any number of men; first, because they would be in each other's way, and second, because the steam shovel can lift single pieces of rock weighing 5 or 10 tons with effortless ease. Of recent years, internal-combustion engines and electric motors have displaced steam as a motive power in many instances; and of course the detailed design of the shovels has been improved immensely. Whereas the largest dippers used 30 years ago had a capacity of 3 ½ to 4 cu. yd., today the 350-ton shovel used at Chino has an 8-yd. dipper, as has the 320-ton shovel at Chuquicamata. Incidentally, for stripping at coal mines a shovel having an 18-yd. dipper is in use. However, the principle of operation of the modern shovel, regardless of the size and type of motive power, is essentially the same as that of the earlier shovels. It is fair to say that the indispensable of open-cut mining is the steam shovel, or, to be more precise, if perhaps less picturesque, the power shovel. Somehow the electric shovel seems to lack the glamour that

Jan 1, 1933

By Allen J. Johnson

It is probable that the word "anthracite" was derived from the Greek preposition an, and the Greek word for Thrace, meaning, in combination, "toward or near Thrace." Aristotle, Theophrastus, Strabo and Pliny all mention Thrace, or Samothrace, in treatises upon stones and stone coals dating back to about 371 B.C. In 1769 Obadiah Gore, a blacksmith of Wilkes-Barre, successfully burned anthracite in his forge, the first of millions of consumers of Pennsylvania anthracite. The Anthracite Region While anthracite is found in widely scattered locations throughout the world, 99 per cent of the total production of the United States origintitles within an area of 3300 square miles in castern Pennsylvania, less than 500 square miles of which arc underlain by workable coal beds. Eminent authorities such as the United States Geological Survey agree that this Pennsylvania anthracite is the only true anthracite east of the Rocky Mountains. There is some graphitic anthracite in Rhode Island but it is not suitable for combustion; and coals from such states as Virginia and Arkansas, frequently sold as anthracite, are in reality semi-

Jan 1, 1934

By James F. Kemp

(San Francisco Meeting, September, 1915) THE iron ores of southeastern Cuba present a subject of exceptional geological interest. Their relations to the inclosing rocks are varied and in some cases unusual. The problem of their geological origin is not a simple one and for this reason has occasioned some divergence of views among previous observers. Profiting, however, by. these earlier studies and by more detailed field and laboratory observations as well as by the experience of added years of mining, much more satisfactory descriptions and interpretations can now be prepared. PREVIOUS WORK In 1884, interest in the southeastern coast of Cuba became active among the consumers of iron ore along the Atlantic seaboard of the United States. Active development was undertaken by the Juragua Iron Co., Ltd., a corporation affiliated with the Bethlehem Steel Co., and the Pennsylvania Steel Co. The property of the Juragua company, which is situated about 15 miles east of Santiago, was studied in June and July, 1884, by Dr. James P. Kimball, at the tine Professor of Economic Geology in Lehigh University and one of the best known of American mining geologists. Dr. Kimball published on his return two papers, the first important descriptions which we have of the local geology.1 It is

Jan 9, 1915

By J. S. Levine, M. Prats

A homogeneous and uniform cylindrical reservoir containing oil and gas is fractured vertically on completion and is produced at a constant bottom-hole pressure. The fracture has an infinite flow capacity, is of limited lateral extent and is bounded above and below by the impermeable strata defining the vertical extent of the reservoir. Results show that such a fractured reservoir can be represented by a reservoir of circular symmetry having very nearly the same production history. The well radius of this circular reservoir is about 1/4 the fracture length and is essentially the same as that obtained previously for a single fluid of constant compressibility. At the same value of cumulative oil production, gas-oil ratios of fractured reservoirs producing at constant terzinal pressure are larger than those of reservoirs having no fractures. This leads to more inefficient use of the reservoir energy in fractured wells and results in lower reservoir pressures for the same cumulative oil production. The reduction in operating life due to fracturing a reservoir is not as great as that for a slightly compressible fluid. This diflerence can be accounted for by the lower reservoir pressure in the fractured reservoir and its adverse effect on the average mobility and compressibility of the oil. As anticipated, the reduction in operating life increases czs the reservoir permeability decreases. The type of results presented in this report can be used to determine the economic attractiveness of fracture treatments per se, to setect the initial spacing to be used in developing a field, and to compare the relative merits of fracturing available wells and infill drilling. INTRODUCTION The effect of vertical fractures on a reservoir producing either an incompressible or a compressible liquid has already been discussed in the 1iterature.l,2 Those results indicate that the production history of such a reservoir is essentially the same as that of a circular reservoir having an effective well radius of approximately one-fourth the fracture length. The present work reports on the effect of a vertical fracture on a reservoir producing two compressible fluids —oil and gas—by solution gas drive. Because of the empirical nature of the PVT and relative permeability data used to obtain the performance of such reservoirs, results can only be obtained numerically and with the aid of high-speed computers. Since reservoirs lose their radial symmetry when fractured vertically, pressure and saturation can no longer be given only in terms of distance from the well. Two coordinates (such as x and y) must now be used to describe the pressure and saturation within the reservoir, and, since we are dealing with compressible fluids, time is also a variable. Thus the solution of a vertically fractured reservoir requires finding two unknowns (pressure and saturation) in two space variables (say x and y) and in time (t). Since no means are readily and generally available for solving such problems at the present time, we have used the results of previous work1,2 to approximate the effect of a vertical fracture on a reservoir producing both oil and gas by depletion. The purpose of the present wmk, then, is to investigate the possibility of using available numerical techniques (limited at the moment to one space variable) to study the two-space-variable flow behavior resulting from a vertical fracture. Results obtained in the course of this investigation are also reported and discussed. Input and output data of the numerical methods used are given in practical units: BOPD, feet, psi, cp, and md. Results are discussed fist in terms of specific reservoir and crude properties and geometries. Later, dimensionless parameters are introduced in order to extend results to different values of some of the reservoir and fracture properties. IDEALIZATION AND DESCRIPTION OF THE FRACTURED SYSTEM It is assumed that a horizontal oil-producing layer of constant thickness and of uniform porosity and permeability is bounded above and below by impermeable strata. The reservoir has an impermeable, circular, cylindrical outer boundary of radius r,. The fracture system is represented by a single, plane, vertical fracture of limited radial extent, bounded by the impermeable matrix above and below' the producing layer (reservoir). It is assumed that there is no pressure drop in the fracture due to fluid flow. 1 indicates the general three-dimensional geometry of the fractured reservoir. Gravity effects and the effects of differential depletion resulting from variations in hydrostatic head (pressure) will be neglected. Thus, the flow behavior in the fractured reservoir is described by the

By Robert M. Betts

The Cornucopia district is situated in northeastern Oregon 25 miles from the Snake River branch of the Oregon Short Line R.R. and 75 miles northeast of Baker City, in the Wallowa Mountains. The formation is principally granodiorite, which has intruded much older rocks locally known as greenstone, and which are probably altered schists. In the upper horizons of the veins, greenstone is found as inclusions in the granitic mass. Both of these formations have been cut by numerous basalt, aplite, and porphyry dikes. Veins of the district are the result of faulting and the consequent crushing of the wall rock. The ore has been deposited irregularly along these faults and formed a lenticular type of vein. The ore varies in width from a few inches to 20 ft.; the average stoping width is about 5 ft. As the basaltic dikes are subsequent to the ore deposition, they are at times a hindrance in development and mining operations; on the other hand, a dike which has followed a vein as a line of least resistance often serves as a good mall in place of the crushed, rather loose granite. The veins generally strike northeast-southwest and dip about 35" to the west. Orebodies are from 100 to 300 ft. in length and about the same in height. The lenses are irregular; inclusions of wall rock are common in the ore and are a factor in reducing the grade. The ores are quartz, carrying some free gold near the surface, but the metals for the most part are in iron sulfides, sometimes associated with chalcopyrite. The gold and silver are in a mechanical combination with the iron, which requires find grinding to liberate them. The ratio of silver to gold is 5 to 1, by weight. Development The Cornucopia Mines Co. owns, and operated until 1920, two mines and two mills of 100 tons capacity each. The sustained high costs and labor shortage, however, necessitated the abandoning of the Union mine, the oldest in the district. Two crosscut tunnels were then started, first, to cut the Last Chance vein at a much lower horizon and, second, to prospect two parallel veins. The ore from the Last Chance vein will go to the old Union mill and the ore from the new veins to the Last Chance mill.

Jan 1, 1925

By John L. Lamont, Walter Crafts

SELECTION of an alloy steel for a heat-treated article has been facilitated by methods for the calculation of hardenability,1 as-quenched hardness,2,3 and tempered tensile strength.4 Ductility and toughness may also be estimated if the steel is completely hardened on quenching,5,6 and the present study was carried out in order to develop a basis for estimating the Izod impact strength of partially hardened steel. The investigation was directed toward the prediction of Izod impact strength in steels of normal commercial quality without consideration of special compositions or heat-treatments that might produce abnormal brittleness. It was found that Izod impact strength of alloy steel is controlled by hardness, degree of hardening on quenching, and grain size. In fine-grained steels the impact strength for any given degree of hardening is inversely proportional to the tempered Rockwell C hardness, and the relation of impact strength to hardness is lowered by incomplete hardening. Calculation of the tensile strength and impact strength of heat-treating steels has shown that, except at very high strengths, tensile strength is raised by alloys without loss of impact strength whereas the tensile strength gained by higher carbon contents tends to be accompanied by a disproportionate loss of toughness. Plain carbon steels give relatively low and unpredictable impact strength. The calculation is sufficiently accurate to be helpful in the selection of alloy steel, and common grades of alloy steel have been evaluated with respect to combinations of tensile strength and impact strength attainable after heat-treatment in sections from I to 4 in. in diameter. PROCEDURE The study of the relation of hardness to impact strength was based on test data derived from 24 heats from four producers. The steels included the following SAE and AISI compositions: 1020, 1o30, 1040, 1340, 3310, 3316, 4320, 4330, 4340, 8620, 8630, 8640, 8720, 8730, 8740, 9310, 9317, 9440, 9917 and three high-alloy chromium-nickel-molybdenum steels. As far as is known, the steels tested were of normal commercial quality. They were supplied in 4-in. sections, which were forged to smaller sizes, prenormalized, and machined to final dimensions. Heat-treatment was carried out by heating to the usual austenitizing temperature for the grade of steel, holding for one hour per inch of thickness and quenching in still oil at room temperature. Previous work had indicated that this quenching treatment approximates a severity of H = 0.35. The bars were tempered as follows: ½ in., I in., and I 5/8 in., 2 hr; 2 ½ in., 3 hr; 4 in., 5 hr. All bars were air-cooled from the tempering tem-

Jan 1, 1947

Jan 1, 1911

By Henri V. Reibell

Deep open pit optimization supposes very long and sedious calculations in order to assign the best shape of the pit and the best bottom level, which will give the biggest profit. Computers give the possibility to make these calculations. More over, they allow to multiply trial calculations so that it is possible to obtain more reliable results. The paper does not expose the computer program but only the way in which mining engineers can use it.

Jan 1, 1969

By Paul C. Merritt

Chrysotile asbestos producers in Quebec may soon experience a unique situation-i.e., strong competition from American ore sources for the short fiber market west of the Mississippi River. This com- petition will be forthcoming from Copperopolis and Coalinga, two deposits now being developed on opposite flanks of the San Joaquin Valley in central California. The combined output now planned from both deposits is 100,000 tons annually, equivalent to about 50% of the annual market demand in the western, central and Gulf States, and more than twice the tonnage sold in 1960 by all other American asbestos producers combined. The principal companies involved in these new undertakings are Jefferson Lake Asbestos Corp. (subsidiary of Jefferson Lake Sulphur Co.), Hidden Splendor Mining Co., Coalinga Asbestos Co. (Johns- Manville Corp. in conjunction with Kern County Land Co.), Union Carbide Corp., and Asbestos Corp. Ltd. Jefferson Lake's principal interest is at Copperopolis where the company's new 70,000-ton per yr mill recently went on stream. The company also holds some claims at Coalinga, but this latter area is better known as the site where Hidden Splendor, Coalinga Asbestos Co. and Todd Industries (a local company) have established operating mines and mills capable of turning out 30,000 tons of fiber each year. Coalinga is also the site of exploration by Union Carbide Nuclear and Asbestos Corp. Ltd.

Jan 9, 1962

By S. F. Radtke, J. A. Snyder, R. M. Scriver

An automatic, continuous casting arc furnace employing a nonconsum-able electrode and a direct current arc has been constructed and operated successfully for titanium. A comparison of the properties of arc and induction-melted titanium indicates that where high ductility, formability, and toughness are required, arc-melted metal is preferable. BECAUSE of the reactivity of titanium metal with all known refractories and the common atmospheric gases, melting of the metal presents numerous problems. It is necessary to provide an inert atmosphere in the furnace as well as a crucible material that will not react with the molten metal, if a ductile ingot is to be produced. Two special furnaces have been developed that meet the requirements and one, the induction heated graphite furnace, has been described in some detail.' Little information is available for sizable units wherein power is applied to the melt through an arc, and the dearth of technical information on such a furnace prompted this report. It has been demonstrated clearly that arc melting produces titanium metal with superior toughness, ductility, and formability. To produce titanium ingots with these properties, an automatic, continuous casting arc furnace has been developed and is described herein. The history of arc melting may be traced to 1800, when Sir Humphrey Davy2 first experimented with Volta's electric battery and found that light could be produced and an arc formed between two carbon points attached to the cell. The discovery of the arc was followed by the design and construction of an arc furnace by Napier," in 1845, for the reduction of metal oxides. In 1853, Pichou' described a similar furnace, although it was not until the discovery of the dynamo in 1867 that the arc furnace could achieve commercial significance. In 1878, Siemens- esigned the first arc furnace intended for the melting of metals and by 1882 had melted steel and platinum successfully. . This was followed by Moissan's" classical work with the arc furnace in 1892. W. von Bolton,' in 1905, found that the arc furnace was suited admirably for melting refractory metals. In his work with tantalum, no suitable refractories for retaining the molten metal were found to exist. Together with Otto Simpson, he developed an arc furnace with a water-cooled copper crucible in which tantalum could be melted without contamination. This technique proved eminently successful. In his paper on the preparation of ductile titanium, Krolle first described an application of the von Bolton furnace to the melting of this metal. The

Jan 1, 1952

By David White

IN these days, when detailed investigations of stratigraphy, structure, and sand conditions so frequently result in the discovery of new oil fields, and applause from oil companies and the public, geologists do well to walk humbly, and punctiliously to admit that the geologic principles controlling the distribution of oil and gas have as yet been discovered only in part, and that what remains yet to be learned is probably vastly more than what is already known. The few experiments already at-tempted have been fragmentary, and somewhat desultory, and however positive each of us may be with respect to certain theoretical conclusions, many of the fundamental questions as to the origin and mode of occurrence of petroleum are subject to radical disagreement. Of the chemical changes attending the generation of petroleum from organic matter, little is actually known. Most of the postulated formulas are liable to be misleading, through ignorance of essential factors. Open-mindedness is therefore a prime essential at the present stage of our science. Nevertheless, adopting the hypothesis that oil originates in some manner fundamentally connected with the organic theory, and in possible departure from such open-mindedness, the writer will pay no attention to the so-called inorganic theory, since every attempt to apply this theory to the study of old oil fields, or to the discovery of new ones, affords cumulative evidence of its inadequacy. In this paper, some of the factors affecting the occurrence of petroleum that the writer believes worthy of consideration by the prospector for oil in any new region will be discussed. Some of these, which are less generally understood, will be considered somewhat in detail. Other points, the significance of which cannot now be determined, require more field study, and for that reason are here brought to the attention of the field geologist. On the other hand, certain theoretical points which do not bear especially on the oil possibilities of a new region will be given little

Jan 2, 1920

By C. F. Wang

Manchuria in General Manchuria, called the "Three Eastern Provinces" in Chinese, forms the northeastern corner of China and is bordered by Siberia on the north and northeast, and by Korea on the east. It is a land famous in Chinese annals as the place of origin of the Ching dynasty, and in more recent times it has been an arena for diplomatic maneuvering and commercial competition between the Russians, advancing from the north, and the' Japanese from the southeast. It derives its name of "three eastern provinces" from the fact that it is divided into three provinces; Hei-

Jan 2, 1918

By Selma Hermann

For the past century, the so-called aluminum bronzes have been assuming a role of ever-increasing importance in the metallurgical field. The last quarter of that century has marked many efforts to find alloying elements that would alleviate some of the undesirable qualities of the aluminum bronzes-for example, the heterogeneity of the alpha solid solution and the extreme hardness of the beta. Much of this work, however, has been rather haphazard-compositions and heat treatment are usually so much at variance as to make comparison impossible. It is the object of this research to study the effect of certain percentages of common alloying elements on aluminum bronzes of analogous compositions and heat treatments. It is hoped that the material gathered here will at least serve as a basis for further systematic study.

Jan 1, 1930

By Herbert Clark Hoover, Lou Henry Hoover

SINCE I have written of the varied work of pre- paring the ores, I will now write of the various methods of smelting them. Although those who bum, roast and calcinea the ore, take from it something which is mixed or combined with the metals ; and those who crush it with stamps take away much ; and those who wash, screen and sort it, take away still more; yet they cannot remove all which conceals the metal from the eye and renders it crude and unformed. Wherefore smelting is necessary, for by this means earths, solidified juices, and stones are separated from the metals so that they obtain their proper colour and become pure, and may be of great use to mankind in many ways. When the ore is smelted, those things which were mixed with the metal before it was melted are driven forth, because the metal is perfected by fire in this manner. Since metalliferous ores differ greatly amongst themselves, first as to the metals which they contain, then as to the quantity of the metal which is in them, and then by the fact that some are rapidly melted by fire and others slowly, there are, therefore, many methods of smelting. Constant practice has taught the

Jan 1, 1950

By A. E. Gorum, J. Washburn, E. R. Parker

Experimental evidence was obtained in support of the idea that cleavage fracture can be initiated by dislocation pile-up. The high ductility of MgO crystals when tested in bending comPared to their relative brittleness in tension was explained on the basis that large pile-ups are more likely in a tension specimen. CLEAVAGE fractures have been a problem of major concern for many years. A number of large steel structures have failed in a brittle manner, usually suddenly and without warning; often the failures occurred for no obvious reason and at nominal stress levels well within the generally accepted range. A great deal of data have been collected about factors that contribute to failures,1 but the physics of the fracture process has never been revealed. cottrel12 has recently developed a theory of brittle fracture in ductile materials which was based upon the concept that dislocations moving on two intersecting planes can unite to form a crack nucleus. This theory accounts for the known effect of grain size and for the effect of testing temperature. There has, as yet, been no experimental evidence published that would substantiate this or the earlier theories based on stress concentrations due to piled-up dislocations. The study reported herein was conducted to obtain information that would either substantiate or disprove the

Jan 1, 1960

By Rees D. Rawlings, C. W. A. Newey

The aging characteristics of an Fe-11 at. pct Mo alloy have been studied by means of light metallography together with density, Young&apos;s modulus, and hardness measurements. The results were consistent with the precipitation of a single intermetallic compound during aging; overaging was slow relative to that in other iron-based binary alloys. The solution treatment temperature had a small effect on the rate of hardening whereas deformation prior to aging had a marked effect on both the rate of hardening and the peak hardness. The density data indicate that the compound precipitated is Fe3MO2 and not the Laves phase Fe2Mo. Analysis of the modulus and density results gave values for the time exponent for precipitate growth of approximately 1.0 and 1.5 for the alloy aged with and without prior deformation, respectively. DETAILED studies of precipitation hardening in bcc matrices have been confined largely to the effects of carbides and nitrides. In view of this and the growing technological interest in intermetallic compound strengthening, e.g., in maraging steels, a study of precipitation in iron-based alloys with a low interstitial content has been undertaken. This paper is concerned with the aging behavior of an Fe-11 at. pct Mo alloy; the mechanical behavior of the alloy will be reported later. The early work of sykes on Fe-Mo alloys showed that precipitation of the intermetallic compound was accompanied by an increase in hardness and a decrease in volume of the material. More recent surveys of the strengthening associated with precipitation have been made3-5 and, in particular, Elsen and wassermann4 showed that deformation prior to aging increased the rate of hardening. These latter workers also followed the precipitation process by means of dilatometry, electrical resistivity, and lattice parameter measurements. Their results confirmed that there is a decrease in volume on aging. Except for the work of Hornbogen on an Fe-20 at. pct Mo alloy, neither clustering nor the precipitation of a nonequilibrium phase has been observed in Fe-Mo alloys. Studies of alloys of lower molybdenum content475 indicate that the equilibrium intermetallic compound is precipitated during aging. However, there is some doubt concerning the nature of the equilibrium precipitate phase. According to the phase diagram constructed by Hansen,8 the phase should be precipitated. This phase has a rhombohedra1 crystal structure which is characterized by the formula Fe706,&apos; although the composition of the molybdenum-rich boundary corresponds approximately to Fe3Mo2. The version of the diagram proposed by Sinha, Buckley, and Hume-Rother indicates that the A phase, a Laves phase Fe2Mo, should be precipitated. Their observation of a Laves phase supports the earlier findings of Bechtoldt and Vacher,13 although, in a recent study of the system by means of diffusion couples, Rawlings and Newey did not detect the phase. The work presented here describes the effect of solution-treatment temperature, aging temperature, and prior deformation on the aging characteristics of the alloy as revealed by light metallography together with hardness, density, and Young&apos;s modulus measurements. In addition the density data are used in an attempt to determine the compound precipitated during aging. EXPERIMENTAL PROCEDURE A 29-kg ingot of the alloy was cast at R.A.R.D.E., Fort Halstead, from deoxidized, Japanese electrolytic iron and sintered molybdenum. The ingot was homogenized for 6 hr at 1473°K and then worked, with intermediate anneals, into 6- and 16-mm-diam rods and 6-mm plate. Chemical analysis of the alloy gave, wt pct: Mo, 17.5 (11 at. pct); C, 0.003; Si, 0.002; S, 0.005; P, <0.002; and02, 0.0098. Solution treatments were carried out under a dynamic argon atmosphere in a vertical, "crusilite" element, furnace which had a facility for rapid quenching into iced water. Except for the study of the effect of solution treatment temperature, all specimens were solution-treated at 1573" * 2°K for 1 hr. Salt baths were used for the aging treatments. Specimens for hardness, density, and Young&apos;s modulus measurements were produced, after heat treatment, from the stock rod or bar using a precision silicon carbide slitting wheel. As described later, the quenching treatment produced local plastic strain in the stock material; consequently, care was taken to ensure that the specimens were not prepared from these regions. Those specimens used in the studies of the effects of prior deformation on the aging behavior were strained in compression in a Denison universal testing machine. Specimens for light metallographic observations were mechanically polished on successively finer grades of diamond paste down to and then etched in either alcoholic ferric chloride or in a 2 pct nital solution. Vickers diamond pyramid hardness data were obtained using a 30-kg load. At least five impressions were averaged for each determination. Density measurements were made using a displacement technique in which each specimen was weighed in air and in dibromoethane at 296°K. The specimens were cylindrical and weighed 3 to 4 g; all weighings were made on a balance reading to 1 x 10"5 g. For each specimen the mean value of five weighings was used to calculate the density. The density of the dibromoethane was determined using the displacement procedure and a standard nickel specimen. The error in an absolute density value was estimated to be HI.01 pct. To obtain the density as a function of aging time a single specimen was used and the density meas-

Jan 1, 1969