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By Richard Miller

The investigations of large-grained specimens carried out by Polanyi and Schmid,1 Sykes,2 Goucher,3 Yamaguchi,4 Gough, Cox, and Sopwith,5 Carpenter and Elam,6 Aston,7 and others have shown qualitatively that grain boundaries restrain the deformation of adjacent crystals. But whether or not the influence of the grain boundary is confined to the glide planes intersected by the boundary has not been demonstrated in any of these investigations, nor has there been carried out any quanti-tative analysis, of the influence of a boundary on the deformation of a crystal. Indeed, the specimens employed in the previous work con-

Jan 1, 1934

Executive JOHN R. SUMAN, Chairman PAUL D. MERICA, Vice-Chairman CHESTER A. FULTON W. M. PEIRCE H. Y. WALKER Finance H. T. HAMIL'T'ON, Chairman ERLE V. DAVELER HENRY KRUMB Admissions FELIX E. WORMSER, Chairman GEORGE D. BARRON, Vice-Chairman PHILIP KRAFT EDWARD MEAGHER CLYDE E. WILLIAMS

Jan 1, 1941

By V. T. Stringfield

ONE of the earliest investigations of ground water in Florida was made in 1513 when Ponce de Leon arrived at St. Augustine in search of the Fountain of Youth. The history of the development of the water resources of the State shows that the large artesian reservoir that underlies Florida was discovered in the latter part of the last century. Part of that history is given by L. C. Johnson1 who states that the first successful artesian well in Florida was drilled at St. Augustine between 1880 and 1882. After the City of Jacksonville failed to obtain a flow of artesian water at a depth of nearly 400 ft and abandoned the drilling, R. N. Ellis, City Engineer, and L. C. Johnson, using Johnson's knowledge of the geologic structure of the artesian reservoir, estimated correctly that artesian water could be obtained at a depth of about 500 ft. Thus began the development of the large artesian system in the northeastern part of the State. In 1908, the Florida Geological Survey issued its first report on the ground water of central Florida.

Jan 6, 1951

By C. D. Tedmon, D. P. Ferriss

THE yield stress, o of low-carbon steel has been shown to vary with the average grain diameter, d, according to the relation1-3 where o is taken to be the lower yield-point stress Of is the friction stress on an unlocked dislocation, and ky is a constant. The interpretation2,4 of ky in terms of dislocation theory relates this constant to the stress to unlock a source across a grain boundary. cottrel14 predicted that ky would increase with decreasing temperature. This was observed to be the case by Adams and coworkers5 in their investigation of niobium (columbium). However, petch6 and Backofen: both working with low-carbon steel, found ky insensitive to temperature. In his work with high-purity niobium, Johnson' found ky equal to zero. Evansg showed that k, was essentially zero for niobium containing nitrogen in an appreciable concentration range. The present experiments were designed to check this apparent anomaly in the value of ky in another Group V metal. Yield points were determined as a function of grain size at several temperatures for tantalum and a tantalum-tungsten alloy. The material used was double are-melted tantalum and a double are-melted alloy of 90 pct Ta and 10 pct tungsten (by weight), both obtained as unannealed, swaged rod. The impurity content of the materials is given in Table I. The tantalum was annealed at 1325"C. in a vacuum resistance furnace using a tantalum boat. The alloy was similarly annealed at 1660°C. Annealing times varied from 15 min to 2 hr, depending on the desired grain size. Nominal pressure in the furnace was 3 X 10~4 mm of Kg. Metallographic examination showed that the annealing treatment produced grain sizes ranging frorn 0.021 to 0.200 mm in the tantalum, and 0.060 to 0.160 mm in the alloy. Tensile bars were made by centerless grinding the annealed specimen;, and then electropolishing to remove all grinding marks. The specimens were than pulled :it 2 1/2 pct per rnin in an Instron testing machine. The tantalum specimens were tested at 77", 195", and 300°K. The alloy was tested at 300°K only. All specimens exhibited a yield-point phenomenon at all temperatures. Typical load-elongation curves at the three test temperatures are shown in Fig. 1. The lower yield stress is plotted as a function of (grain size) in Figs. 2 and 3 for tantalum and the 90 pct Ta-10 pct W alloy, respectfully. The position and slope of the curves was determined by least-

Jan 1, 1962

Truman H. Aldrich John H. Allen W. Lawrence Austin W. S. Ayres John Henry Banks Wm de L. Benedict Robert Bentley Andrew A Blair Walter M. Brodie

Jan 1, 1934

By Henry N. McCarl

Mineral aggregates are those natural and manufactured industrial mineral and rock materials that provide bulk and strength in port- land cement concrete, bituminous concrete mixes, and plaster or stucco surfaces. They may also provide special characteristics such as thermal and acoustical insulation, weight, surface textures, abrasion resistance, and impermeability to various concrete products and mixes. Most aggregates are relatively inexpensive materials, but despite their low unit value, the tonnages consumed each year in the United States and throughout the world make mineral aggregates by far the leading industrial mineral and rock materials both in terms of volume (tonnage) produced and value consumed. The major use of mineral aggregates is in concrete. The low cost, high bulk aggregates tend to keep concrete construction costs at levels competitive with other building materials. Other major uses of aggregates include highway and railroad base or ballast materials, graded fill, and various industrial uses such as metallurgical and chemical fluxes and raw materials-these latter uses are often considered nonaggregate uses of mineral aggre- gate materials. The value of mineral aggregate materials at the production plant varies from less than a dollar per ton to several dollars per ton for most crushed stone and sand and gravel, $2 to $15 per ton for slag and expanded clay or shale aggregate, to as much as $60 to $100 per ton for expanded perlite or vermicu- lite. The more specialized the use, the higher the price-although there are naturally some exceptions to this rule of thumb. The first four parts of "Construction Materials" deal with the utilization of four major mineral aggregate types: Crushed Stone, Light- weight Aggregates, Sand and Gravel, and Slag. While the focus will be on the use of these industrial minerals and rocks there will also be some coverage of sources, mining and production, especially in those cases where they are

Jan 1, 1975

NEVADA SECTION J. W. HUTCHINSON, Chairman, FRANCIS CHURCH LINCOLN, Vice-Chairman, HENRY M. RIVES, Secretary-Treasurer, Reno, Nevada W. H. BLACKBURN, E. A. JULIAN, EMMET D. BOYLE, JOHN G. KIRCHEN, FREDERICK BRADSHAW, C. B. LAKENAN, TASKER L. ODDIE. The formation of the Nevada Section was originally suggested by Professor F. C. Lincoln, who had discussed the subject with Mr. William L. Saunders when the latter was President of the Institute. Professor Lincoln sought the assistance of the Nevada Mine Operators' Association, whose Executive Committee constituted itself a Committee on Organization, and authority for the establishment of a Nevada Section to include the entire State was secured from the Board of Directors of the Institute. The formal installation took place at 10 A.M. on May 18, Mr. William L. Saunders officiating. The Honorable Emmet D.. Boyle, Governor of Nevada (and a member of the Nevada Section), made the address of welcome. On the afternoon of the same day, a technical session was held, at which the following papers were presented: History and Development of the Cyanide Process Charles Butters Virginia City Whitman Symmes Ore Deposition at Steamboat Springs Prof. J. C. Jones

Jan 7, 1916

Boiler-Room Economy "Establishing and Maintaining Boiler-room Economy" is the title of a paper presented before the Ohio Society of Mechanical Electrical and Steam Engineers by Geo. H. Gibson, of which the following is an excerpt: Boiler-room economy depends less upon equipment than upon operation, i.e., it depends largely upon the condition in which the apparatus is maintained and how it is used. A given boiler may operate this week with an efficiency of 78 per cent., and next week with an efficiency of 65 per cent., while using the same fuel and developing the same rating. If there are variations ii; character of fuel and in load and other factors, the falling-off may be even greater, possibly to less than 60 per cent. The steam produced may cost twice as much per 1,000 lb. at one time as at another. Most steam plant managers know from their own experience that these statements are not exaggerated. It does not take much of a plant to run up a coal bill of $5,000 per year, many "spend $10,000 for coal, and fuel bills of $50,000, $100,000, or $200,000 per annum are not uncommon. As it call be shown in the majority of these plants that 10 per cent. of this amount may be saved, and in large numbers of them 25 per cent., while in some the expenditure can be cut in half, there is no disputing that we have here a subject worthy of attention. In the production of steam the greatest variable is the human factor. Before we can pass judgment, however, we must first have standards. This implies accurate quantitative knowledge of fuel consumption and steam production. We must measure the output and know how much the steam costs per thousand pounds, and how many pounds of steam are obtained from a pound of coal. We can then begin to analyze the problem, and find where and how methods and conditions can be improved, and how much. Many favor buying coal on a B. t. u. basis. This is advisable where the amount purchased warrants the considerable expense involved in systematically gathering samples that: are. truly representative and in having analyses made, of every carload. Coal analyses, combined with. an honest endeavor on the part of the miner to ship good coal, should insure the receipt of the heat units paid for. , It often happens, however, that the coal which is cheapest on a B.t.u. basis is not the cheapest or most suitable for producing steam, because of peculiarities of the plant in which it is to be burned, or conversely, the fuel which furnishes cheap B.t.u. may require special methods or equipment for its economic utilization.

Jan 2, 1916

By Joseph E. Pogue, F. G. Coqueron

Prior to 1934, published information covering expenditures by oil companies for properties, plant, and equipment and the residual investments in the various segments of the petroleum industry was not readily available. This paper presents an analysis of the funds invested by a selected group of oil companies during the years 1934 through 1942, based on an extensive study of the individual records of 30 oil companies. The sources, disposition, and characteristics of the capital employed by this group of companies are traced through a series of combined statements and appropriate charts, covering financial and operating data. The analysis of these statements not only constitutes a record useful for comparative purposes but also serves as a basis for a number of broad conclusions, as follows: 1. The petroleum industry generates the capital needed for its expansion almost entirely from its own operations and is therefore a singularly self-contained economic unit. 2. The long-term debt contained in the financial structure of the industry is small relative to the total capital employed, is less than the net working capital, and has increased but slightly during the period under review. 3. The capital expenditures of the group of 30 oil companies for 9 years amounted to 6.1 billion dollars, 58.3 per cent of which went into crude-oil producing facilities. The trend of this segment of expenditures has been downward since 1937. In 1942, expenditures for refining facilities increased sharply and for marketing facilities declined drastically. 4. The net working capital of the group increased 380 million dollars over the period, and the industry is in a favorable position of liquidity. The ratio of combined current assets to current liabilities was 3.21 at the close of the period. 5. The net income of the group displayed an upward trend for the period but with rather sharp cyclical fluctuations. 6. In 1942, Government funds entered the industry for the first time in substantial amounts and were utilized for the provision of war facilities needed for emergency use. 7. The group has paid out a relatively low percentage of net income in the form of dividends. For the period the average was 55 per cent of net income. 8. The rate of return on invested capital for the group averaged 6.4 per cent for the

Jan 1, 1944

By Joseph E. Pogue, F. G. Coqueron

Prior to 1934, published information covering expenditures by oil companies for properties, plant, and equipment and the residual investments in the various segments of the petroleum industry was not readily available. This paper presents an analysis of the funds invested by a selected group of oil companies during the years 1934 through 1942, based on an extensive study of the individual records of 30 oil companies. The sources, disposition, and characteristics of the capital employed by this group of companies are traced through a series of combined statements and appropriate charts, covering financial and operating data. The analysis of these statements not only constitutes a record useful for comparative purposes but also serves as a basis for a number of broad conclusions, as follows: 1. The petroleum industry generates the capital needed for its expansion almost entirely from its own operations and is therefore a singularly self-contained economic unit. 2. The long-term debt contained in the financial structure of the industry is small relative to the total capital employed, is less than the net working capital, and has increased but slightly during the period under review. 3. The capital expenditures of the group of 30 oil companies for 9 years amounted to 6.1 billion dollars, 58.3 per cent of which went into crude-oil producing facilities. The trend of this segment of expenditures has been downward since 1937. In 1942, expenditures for refining facilities increased sharply and for marketing facilities declined drastically. 4. The net working capital of the group increased 380 million dollars over the period, and the industry is in a favorable position of liquidity. The ratio of combined current assets to current liabilities was 3.21 at the close of the period. 5. The net income of the group displayed an upward trend for the period but with rather sharp cyclical fluctuations. 6. In 1942, Government funds entered the industry for the first time in substantial amounts and were utilized for the provision of war facilities needed for emergency use. 7. The group has paid out a relatively low percentage of net income in the form of dividends. For the period the average was 55 per cent of net income. 8. The rate of return on invested capital for the group averaged 6.4 per cent for the

Jan 1, 1944

By Kenneth K. Humphreys

INTRODUCTION What is automation? Why automate? Webster's New Collegiate Dictionary defines automation as "the automatically controlled operation of an apparatus, process, or system by mechanical or electronic devices that take the place of human organs of observation, effort, and decision." This definition gives an implied answer to the second question, "Why automate?" Automation, automatic control devices, and process control equipment receive their justification in supplementing or replacing manpower, which results in decreased operating costs. In the past, processes were operated with the minimum amount of instruments needed merely to guide operators. Processes were manually con- trolled by the operator on the basis of simple temperature, pressure, flow, and level indications on a panel. Today the tendency is to design a new plant to operate in a fully automatic manner according to a preset pro- gram utilizing a minimum of manpower. In addition to this direct cost reduction in manual labor, increased equipment capacity results from uniformity of flow and uniform control of process variables. This control eliminates or minimizes surges and permits equipment to be operated at or near its ultimate capacity and, for a given material throughput, permits the use of smaller process equipment. Automatic control, therefore, be it in the field of coal processing or in any industrial field, is simply a problem of economics. Control equipment is justified in terms of its contribution toward increasing productivity, increasing profit margins, or producing a new and salable product at a profit. Instruments and control devices can be divided into two general groups: (1) units which measure and (2) units which both measure and control a process variable.

Jan 1, 1979

Truman H. Aldrich W. Lawrence Austin W. S. Ayres John Henry Banks Wrn de L Benedict Andrew A Blair Walter M. Brodie H. H. Burden Charles Butters

Jan 1, 1932

S. F. Emmons, Washington, D. C.: Mr. Malcolmson's paper on the intensely interesting deposits of the Sierra Mojada creates a strong desire to visit the region so well described. Although it is difficult to intelligently discuss a locality that one has never seen, I cannot refrain from offering some remarks in the nature of a tentative suggestion: 1. Age of Beds.—Mr. Malcolmson speaks of the enormous thickness of limestone forming the Sierra Mojada as belonging to the Carboniferous series. If this is not a typographical error, it seems that he should present some evidence for such age, for Chism,* in his previous article on the district, says the only fossils found there were said to be Cretaceous; and it is well known by the investigations of R. T. Hill and others that the great thickness of limestone in this part of Mexico is of Cretaceous age. 2. Structure of Mountains.—Mr. Malcolmson presents good reasons for thinking that the structure of the two related mountain masses (Sierra Mojada and Sierra Planchada) is not the simple anticlinal fold given by Mr. Chism's section, it being evident that there has been faulting as well as flexure. I venture to add that the facts presented by Mr. Malcolmson seem to suggest the possibility that, instead of being simply an eroded anticline, the valley between the two ranges may have been formed, in part at least, by the irregular faulting down of the intermediate block, on the surface of which the volcanic breccia had originally accumulated at a higher level. The sections of the Exploradora and the San Josh mines, in the smooth surface of the contact, with clay selvages and the occasional slickensides, certainly suggest a structural fault between the limestone and breccia. The arrangement of some of the

Jan 1, 1902

By W. Rostoker, R. P. Elliott, B. W. Levincer

Phase equilibria in the Ti-Cr-Mo system have been investigated for alloys containing 100 to 40 pct Ti in the temperature range 550° to 1300°C. Five experimental isothermal sections and a surface of incipient melting are presented in addition to a summary projection of the space. Seven vertical sections have been constructed from the isothermal sections. A STUDY of the system Ti-Cr-Mo was undertaken as part of a program sponsored by Watertown Arsenal toward the development of titanium-base phase equilibrium diagrams of potential technical importance to alloy development. The scope of the investigation included the composition range contained by the titanium corner and the line of 64 pct Ti (all compositions are by weight) and the temperature range 550" to 1100°C. A surface of incipient melting was constructed from measurements on a large number of alloys. The system Ti-Cr has been established.&apos;-? The phase diagram is characterized by a wide miscibility field of the solid solution at elevated temperatures and a eutectoid reaction of the type: (15 pct Cr) + TiCr, (685C). The a solid solution has a very limited capacity for solution of chromium (< 0.5 pct Cr). The intermediate phase TiCr2 has at best a very narrow composition range. It has been shown that two allotropic modifications of this phase exist. However, this behavior does not appear to be perceptibly reflected in the form of phase boundaries of the type + TiCr,. In the system Ti-Mo,9-10 the phase is stabilized to successively lower temperatures with increasing molybdenum content. There are no known intermediate phases. The a solid solution is limited to less than 0.5 pct Mo. Because of the very extensive range of the phase, the ternary system was ideally suited to the determination of the phase boundaries by the parametric method of Andersen and Jette." A parametric surface was constructed to provide the necessary basis for the application of this method. Preparation and Treatment of Alloys More than 60 alloy compositions were prepared for the study of this system. Alloy buttons of 10 grams were arc-melted in a nonconsumable electrode furnace using inert atmosphere protection and a water-cooled copper crucible. The construction and operation of this type of melting unit have been adequately described elsewhere.&apos;&apos; To insure complete solution of alloy additions, the buttons were remelted alternately on top or bottom as many as five times. This was accomplished by a suitable mechanism for "flipping" over the ingots. Iodide titanium (99.97 pct Ti) was used as the alloy base. An especially high quality chromium (99.9 pct Cr) was obtained from the National Research Corp. Molybdenum sheet (0.005 in.) of 99.9 pct purity was used.

Jan 1, 1954

By L. S. Richardson, N. J. Grant

Iodide-grade titanium, two oxygen alloys, and two aluminum alloys were studied by means of creep-rupture tests from 1000° to 2000°F. From the test information an evaluation was made of, 1) the relative creep-rupture strengths of the u (hexagonal-close-packed) and 0 (body-centered-cubic) forms of titanium and some of its alloys; 2) the effects of solid-solution strengthening by oxygen and aluminum on the u and 0 structures; and 3) the extent and effect of atmospheric oxygen alloying on rupture life in tests above about 1000°F. THE use of titanium alloys at temperatures above 1000° F has been considered unlikely by most investigators because of low creep strength (based on a requirement for room-temperature ductility, formability, and weldability) and low oxidation resistance. The results of this testing program do not entirely uphold this pessimism in terms of strength and oxidation resistance. The observations described below are based entirely on stress-rupture results, although some creep tests were also carried out on these alloys. Three items of primary importance are covered: 1) Stress-rupture data in the form of the Larson-Miller parameter curves for several titanium alloys at temperatures up to 2000°F; 2) The relative strengths of the hexagonal-close-packed a structure and the body-centered-cubic 0 structure; 3) The effects of solid-solution alloying on the creep-rupture properties of titaniu&apos;m at elevated temperatures. Only two investigatons have reported the creep- rupture properties of titanium at temperatures above 1000° F. Lunsford and rant&apos; tested iodide titanium; their values are also utilized in the paper. EXPERIMENTAL PROCEDURE After a few tests had been made in a conventional creep-rupture test machine, it became clear that some sort of atmospheric protection would be necessary for short-time tests conducted at temperatures above 1600°F, or for times greater than 100 hr at 1200°F or above. Several furnace units and test machines were constructed, the most successful of which is shown in Fig. 1. Certain experimental difficulties peculiar to titanium were encountered; for example, the use of molybdenum holders was dictated because titanium forms low melting-point eutectics with conventional high-temperature alloys containing appreciable amounts of iron, nickel, or cobalt. This same difficulty made the use of chrome l-alumel thermocouples in direct contact with a test specimen impossible, above about 1500" F. The high-temperature high-vacuum furnace shown in Fig. 1 was capable of maintaining a vacuum of better than 10"5 mm of mercury at 2000°F (pressure measured in cold part of system) and 5 X lo-&apos; mm at room temperature. Most of the tests eonducted in vacuum were at temperatures

Jan 1, 1960

(Members are urged to send in for this column any notes of interest concerning themselves or their fellow-members..) Members and guests who registered at institute headquarters during the period Dec. 10, 1915 to Jan. 10, 1916: A. R. Fletcher, Palo Alto, Cal. H. L. Hollis, Chicago, Ill. R. G. Hall,. St. Louis, Mo. Howland Bancroft, Denver, Colo. Walter E. Koch, Terlingua, Tex. G. D. B. Turner, Butte, Mont. George A. Macready, Searchlight, Nev. H. A. Wheeler, St. Louis, Mo. H. W. Edmondson, Concheno, Chili., Mex. George B. Rodgers, St. Francois, Mo. Arthur F. Taggart, New Haven, Conn. Paul S. King, Wilmington, Del. H. V. Winchell, Minneapolis, Minn. G. H. Clevenger, Palo Alto, Cal. Frank A. Ross, Spokane, Wash. J. W. Beard, Syracuse, N. Y. W. D. B. Motter, Jr., Benson Mines, N. Y. Albert De Deken, Louvain, Belgium. S. Le Fevre, Forest Glen, N. Y.. James H. Smith, Jr., Mount Carmel, Pa. E. H. Hamilton, formerly manager of the Virginia Smelting Co., West Norfolk, Va., has become consulting metallurgist to the Consolidated Mining and Smelting Co., of Canada, Ltd., Trail, British Columbia.

Jan 2, 1916

New York Meets first Wednesday after first Tuesday of each month. DAVID H. BROWNS Chairman. JOHN H. JANEWAY, Vice-Chairman. F. E. PIERCE, Secretary 35 Nassau St., New York, N. Y. P. A. MOSMAN, Treasurer. LEWIS W. FRANCIS. BENJAMIN B.. LAWRENCE. Boston Meets first Monday of each winter month. HENRY L. SMYTH, Chairman. ALFRED C. LANE, Vice-Chairman. HENRY A. WENTWORTH, Secretary-Treasurer, 60 India St., Boston, Mass. A. H. EUSTIS, F. G. STANTIAL. Columbia Holds four sessions during year. Annual meeting in September or October. STANLY A. EASTON, Chairman. FREDERIC KEFFER, Vice-Chairman. LYNDON K. ARMSTRONG, Secretary-Treasurer, P. O. Drawer 2154, Spokane, Wash. D. C. LIVINGSTON, FRANK A. ROSS.

Jan 5, 1916

By R. L. Pober, L. Kaufman, E. V. Clougherty

Composite structure of hafnium, zirconium, and titanium diboride with additions of metals and/or compound phases were prepared by reactive high-pressure hot pvessing and evaluated in air and in mixtures of oxygen and helium at temperatures up to 2400°K and at linear flow rates of 0.1 to 0.2 ft per sec stp. Oxidation characteristics, principally depth of conversion of diboride to dioxide, were determined by a gas analysis method and by postoxidation metallo-graphic analyses. The best oxidation resistance was observed for hafnium diboride-silicon carbide composite which exhibited a 6-mil conversion to dioxide for a 1-hv oxidation in air at 2200°K compared to a 20-mil recession for hafnium diboride with no additive. Analogous improvements in oxidation resistance were observed for the addition of silicon carbide to zirconium. EARLIER investigationof the oxidation behavior of the diborides of the transition elements of Groups IVA and VA in flowing gas mixtures have produced a ranking of these compounds according to which HfB2 is the most oxidation-resistant followed in turn by ZrB2 > TiB2 > TaBz > NbB2. Other ~tudies~-~ have examined the physical, thermal, and thermodynamic properties of these diborides to provide a sound basis for the more detailed and specialized investigations which are required to generate the information needed to assess the usefulness of such materials in high-temperature oxidizing environments. Recent oxidation studies7 have examined the effect of variations of metal and boron content on the oxidation characteristics of zirconium and hafnium diboride in flowing gas mixtures including air and helium plus oxygen. Results obtained in the latter investigation confirmed the superior oxidation resistance of HfB2 over ZrB2. Moreover, metal-rich compositions of hafnium diboride showed improved oxidation resistance over boron-rich compositions at temperatures up to 2000°K; at higher temperatures the differences are not distinguishable. In particular HfBI.7 exhibited a diboride to dioxide conversion depth of 4 mils in 1 hr at 2000°K; HfB2. 2 exhibited a conversion depth of 16 mils for the same exposure.~ Specimens for the study of metal and boron stoichiometry on the oxidation characteristics of HfB2 and ZrB2 were prepared by high-pressure hot pressing, a specialized type of fabrication which produced dense crack-free bodies of the desired compositions with no significant impurity introductions. The purpose of the present investigation was to explore the possibility of further improving the oxidation resistance of the metal-rich ZrB, and HfB2. The plan to accomplish this objective was based in the formulation of several diboride compositions containing other compounds and phases which are generally known to have good oxidation resistance in one or more types of test environment. Ideally, such additives would also enhance or at least not diminish other boride property values principally mechanical strength and those parameters related to thermal stress resistance. The additions selected for HfBz included zirconium, aluminum, and (Ta + TaB2) designed to produce ternary metal diborides, hafnium to form a discrete HfB phase, chromium to provide a metal skeletal phase, (Hf + Si) to form a discrete hafnium silicide phase, and Sic to provide a discrete second phase. Additions to ZrB2 included A1 + B designed to produce a ternary metal diboride, Zr + Si to form a discrete zirconium silicide phase, and Sic to provide a discrete second phase. All the specimens were prepared by high-pressure hot pressing which was used to advantage to fabricate billets of the variety of compositions desired and suitable for oxidation testing. The present investigation also included the evaluation of high-pressure hot-pressed TiB2and TiB2-20 vol pct Sic, conventionally hot-pressed Boride 2,&apos; and KT silicon carbide. Boride

Jan 1, 1969

Truman H. Aldrich John H. Allen W. Lawrence Austin W. S. Ayres John Henry Banks Wm de L. Benedict Robert Bentley Andrew A Blair Walter M. Brodie

Jan 1, 1934

By Cuppam Dasarathy

The incidence of liquid inzmiscibility in binar)) indium alloys has been theoretically analyzed on the basis of the Hildebrand-Alott equation. Bedictions of miscibility or otherwise Imve in general been found to agree with those phase diagrams that are already publislzed in the literature. Out of a total of 27 systems, where either the complete phase diagrams are published or liquid immiscible behavior is reported, the Predictions agree with the experimental data in 25 systems, the exceptions being the Te-In and Ni-In systems. According to the equation, liquid immiscibility is also indicated in the binary alloys of indium with K, Rb, Cs, Na, Sr, Ba, Ti, Zr, V. Nb(Cb), Ta, W, U, Re, Ru, Rh, Os, and Ir. RECENT investigations by the author have shown that indium when alloyed with iron, chromium, and cobalt shows liquid immiscible behavior.1"3 The Fe-In phase diagram shows a wide range of compositions where the liquids are immiscible.4,5 No intermediate phases are present in this system. No precise information is available about the extent of liquid immiscibility in the Co-In system. However, it is certain that there is a range of compositions where the liquids are immiscible and that there are two or three intermediate phases,376 in the system. Liquid immiscibility is also strongly indicated in the Cr-In system and no evidence was obtained in the brief investigation to indicate the presence of intermediate Cr-In phases.2 The present paper deals with a theoretical analysis of binary alloys of indium with certain elements of the periodic table and indicates the systems where liquid immiscibility may be expected. The incidence of liquid immiscibility in binary systems has been theoretically examined by many workers and many excellent papers are available on the subject. In this paper, the alloy systems are examined on the basis of the more recent ideas proposed by Mott.7,8 It has been claimed8 that the Mott parameter predicts the incidence of miscibility or otherwise with reasonable accuracy and consistency. BACKGROUND TO MOTT&apos;S APPROACH Hildebrand applied his immiscibility rule for non-polar liquids to various alloy systems.9 The basis of this rule is that the equation for the excess free energy of formation of a liquid solution is rather similar to the theoretical expression for the energy of mixing of a regular solution. He postulated that when the heat of mixing is sufficiently high, separation into liquid phases will occur and the condition for complete CUPPAM DASARATHY is at the Research Centre, British Steel Corporation, (South Wales Group), Port Talbot, Glamorgan, Great Britain. Manuscript submitted March 12, 1969. IMD miscibility was shown as where VA and VB were the atomic volumes of the components A and B, and ?EV the energy of vaporization of the component. The term (?EVA/VA)1/2 was regarded as a measure of the binding energy of the component A and was called the L&apos;solubility parameter" 8A. On this basis immiscibility occurs when 1/2(VA+VB)(bA-bBf > 2RT [2] Apparently, however, there were several inconsistencies in that according to Eq. [2] several systems known to be miscible in the liquid state were predicted as immiscible. MOTT&apos;S ANALYSIS ~ott&apos;" regards that the reason for the inconsistencies arising out of Hildebrand&apos;s equation was largely due to the electrochemical attraction between the two elements, not being considered. Hence, Eqs. [I] and [2] were modified by taking into account the electro-negativities of the two elements XA and XB, and Mott arrived at an equation for immiscibility, i(VA + VB)(6A - aB)2 - 23,Q60n(XA - XBf > 2RT [3j which can be written as i **&£*&* >&apos;*°™- &apos;• HI T being the melting point of the more refractory component of the system. In Eq. [4], the numerator was called the Hildebrand term, the denominator, the electronegativity term, and their ratio, the Mott number. Mott observed that if the Mott number of a given binary system was greater than the maximum number of Pauling bonds which the two metals could form, then liquid immiscibility could be expected. The maximum number of bonds formed by a given metal was considered to be directly related to the number of bonding electrons available, i.e., to its maximum valency. Since the valencies of the elements considered vary from 1 to 6, Mott assumed that if the ratio of the Hildebrand term to the electronegativity term was >6, then immiscibility could be expected. On the contrary, if the ratio is <1, the metals should be miscible. Further, the alloying behavior is not only influenced by the valencies of the two elements but also by the relative atomic sizes that influence the types of packing and hence the coordination number. Mott considers that on average the maximum number of near neighbors of unlike atoms is 6. Thus, on both valency and size factor considerations, Mott concludes that the maximum number of bonds&apos; possible in any system was 6, this being the upper limit of the Mott number for miscibility. In considering the alloying behavior of systems with Mott numbers between 1 and 6, Mott plotted the num-

Jan 1, 1970