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By E. B. Swanson

Frequent reference has been made to the increased domestic gasoline demand recorded for 1931. This increase was in the neighborhood of 7,000,000 bbl. Although smaller relatively than that to which the oil industry had become accustomed by virtue of the experience of preceding years, the increase was of substantial amount, particularly at a time when any increase at all could be regarded with eminent satisfaction. Less has been said, however, of the 18,000,000 bbl. decline in gasoline shipments to territories and foreign countries. When the loss of business outside the United States is combined with the domestic increase, there results a net loss of some 11,000,000 bbl. in total gasoline demand. The gain of 2 per cent in domestic sales gives way to a loss of 2.5 per cent in total domestic and foreign sales. The United States actually has been losing ground in the international gasoline market since 1924, when shipments from this country equaled 72 per cent of the gasoline shipments from the leading gasoline-producing countries of the world. A loss in relative standing was recorded with each succeeding year. As long, however, as gasoline shipments showed an actual increase, the loss in relative standing was of little concern. Foreign producing centers annually supplied an increasing share of the foreign gasoline markets, but, until the past year, the demand abroad continued to increase at a pace which could accommodate all of the increased output of foreign plants and yet require increasing quantities from the United States. It was not until 1931 that the various factors were combined so as to produce an actual and substantial decrease in the foreign demand for United States gasoline. Consumption in foreign countries generally declined, while the output of foreign refineries and the foreign manufacture of substitute fuels continued to increase. From our own viewpoint, this meant a loss of some 18,000,000 bbl. of gasoline business in foreign countries, one-half of it probably due to the lowering in foreign demand and the other half to the increased output of foreign refineries and the increased utilization of substitute fuels.

Jan 1, 1932

By Robert E. Tally

CHAUNCEY L. BERRIEN, Butte, Mont. (written discussion).-Having had much actual experience with mine fires which have occurred or have been active in the mines of the Anaconda Copper Mining Co. during the past 4 years and having lately visited the fire zone of the United Verde mine with Mr. Tally, I wish to congratulate him for the success which he has had in controlling this fire and making the mine perfectly safe .for his miners. By this work he is not only keeping the property in operation but is reclaiming many lost orebodies. The ventilation system as described by him is practically the same as that used under my direction at the Mountain View mine fire in Butte in 1913 and at the Pennsylvania fire in 1916. This same system is at present being followed at the Leonard mine to extinguish a fire which has been active for 10 years although bulkheaded. The mining system in the Butte mine, at the origination of these fires was the same as that at the United Verde, namely, square setting .accompanied by the use of much timber bulkheading in the stopes owing to heavy ground. The pyritic content of the ore in Butte is not as high, but on the whole conditions have been the same, with the exception of actual location of the fire in the mine. I agree with Mr. Tally that flooding, the use of C02 or any gas, and the use of steam are all impracticable unless the fire zone can be absolutely sealed. His system of upcast escapement shafts in the fire zone, the use of bulkheads and fans to keep the gases away from the firemen, must be resorted to. By the method lie describes actual stoping may be carried on safely if started from the bottom of the fire and if the fire zone extends to the surface. In other words, the fire zone must be isolated from the rest of the mine by bulkheads and solid ground, with no ground above which can be damaged by spread of fire or caving. The serious fires in Butte have .occurred on or between levels in the mines where it was necessary to prevent their .extension upward, downward and laterally while the work of actually extinguishing them was in progress. This necessitated proper bulkheading should we lose control of the fire, the installation of ventilation similar to Mr. Tally's and the systematic drilling of holes with diamond drills for distributing water on the fire and around it.

Jan 12, 1916

By E. H. Dix

The success of the Charpy impact test in the steel industry has led those interested in aluminum alloys to investigate the possible application of this test to aluminum and its alloys. In this paper are set forth the results of a few preliminary tests made at the Lynite Laboratories of the Aluminum Manufactures, Inc. In order to study more thoroughly the significance of the Charpy test, slow-bending tests have been made duplicating the arrangement of the impact machine. Tests have been made on both notched and unnotched specimens of a series of copper-aluminum alloys. Apparatus The standard American-made Charpy impact machine delivering a blow of over 200 ft.-lb. was much too large to test aluminum-alloy specimens of the same type used for steel, so that it was necessary either to adopt a larger specimen or to have a special light-weight hammer made. Since there is no known relation between specimens of different sixes, even though geometrically similar, it was decided to adhere to the 10 by 10 mm. specimen. Accordingly, Sauveur and Boylston, the American makers of the machine, were asked to construct a special light-weight pendulum adapted to their standard machine, this pendulum to have one-tenth the capacity of the standard. The writer wishes here to acknowledge his indebtedness to Mr. H. M. Boylston for the personal interest and care exercised in constructing this pendulum. The machine with the light-weight hammer in place is shown in Fig. I. It is mounted on a concrete foundation with the concrete covering the flange on the base of the machine. Vibration is further prevented by four 5/8-in. (15.8 mm.) foundation bolts. The large standard hammer shown against the wall was also used for some of the unnotched bars that required more than 20 ft.-lb. to rupture. When the light-weight hammer was received, it was carefully cali-

Jan 1, 1921

By George I. Adams

PHYSICAL AND CLIMATIC DIVISIONS. PERU is divided into three regions-the coast, the sierra, or high mountainous region, and the a montana," or forest region of the Amazon basin. The Coast.-The coast is an arid region. No rain falls excepting in the extreme northern part, which borders the Gulf of Guayaquil. There is, however, a slight precipitation in the form of mist (garua), which occurs on the coast hills during the so-called winter months. The aridity of the coast is due principally to the antarctic or Humboldt ocean-current, which, being cold and having a temperature lower than that of the land, absorbs rather than produces vapors. The coast mists occur during the season when the land is relatively cold. Near the Gulf of Guayaquil the antarctic current diverges from the coast, so that in the Tumbes valley and adjacent country the conditions in the summer months are such as produce rains. In the remaining valleys of the coast, agriculture is made possible only by means of irrigation, and is accordingly very limited in extent, although rich and varied. In the northern and south-central portions of the coast, plains extend inland from the sea, while in the southern part there is a coastal plain separated from the Pacific by a range of coast hills. Between the northern and south-central plains, as well as between the south-central and southern, the foothills of the sierra descend to the seacoast. The Sierra.-The sierra embraces the high land dominated by the lofty cordilleras of the Andes. In the southern part of Peru there are two cordilleras, the western and the eastern, which enter from Chile and Bolivia respectively, and inclose between them the Titicaca Lake basin. To the north of Lake Titicaca these cordilleras unite in the knot of Vilcanota, south of Cuzco. From this knot three cordilleras, known as the western, the central, and the eastern, extend to the northward, reuniting in the

Jan 7, 1908

By Lawrence F. Rooney

One of Edgar Allan Poe's stories that haunts my subconscious is the Masque of the Red Death. These days, whenever I join a group like this, especially during the cocktail parties, I see myself and others as those mythical swingers seemingly isolated from the plague. The world, but this country especially, has had a ball plundering, spending, and wasting its natural resources for 100 years. And, as in days of yore, it is fitting that we end this ball with spectacular fireworks: trips to the moon, so that our grandchildren, huddled in their caves along the Ohio, will better understand how it all began.

Jan 1, 1970

By Edward Keller

Jan 1, 1906

By A. Werenfels

After discussing the geology of the Limagne, the surface indications of petroleum, and the recent exploration, the author states that none of the wells were properly located and that oil possibilities of the Limagne have not been adequately tested. NO PETROLEUM, in commercial quantities, is found in France except the small production of the Pechelbronn field (Fig. 1) in Alsace, which produced 75,000 tons in 1923; therefore the test of the petroleum FIG. 1.-KEY MAP. prospects of the Limagne is most interesting. Under the superintendence of M. Termier, chief engineer of the French mines, a well near Crouelle (Fig. 2) was drilled in 1921 to a depth of 856.3 m. (2808 ft.); at different depths favorable showings were encountered. The well, however, was abandoned because of drilling difficulties. A second one is now being drilled near the same place.

Jan 12, 1924

By R. C. Ferguson, Harlowe Hardinge

Laboratory and plant data covering 12 different operations show that lower than "standard" ball mill speeds increase grinding efficiency. In the case of high pulp-level mills, the gain is so great that the increase in capital cost of the larger lower speed mill will pay for itself in less than a year's time. THE object of this paper is to show the economic advantage of operating ball mills at relatively slow speeds. Although many operators know that grinding costs are reduced by operating mills at low speeds, they seldom do so for a variety of reasons. When capital is limited, first cost is of primary importance, and installation of the less costly, highspeed mill is favored. When materials are in short supply, as during a war period, capacity rather than economy is the primary consideration. Existing mills are then speeded up to provide the desired increase in capacity, and new mills are purchased without consideration of maximum grinding efficiency. When the mill speed is increased to secure more production, the increase in grinding costs is often obscured by the total benefit derived from the additional output. This increase in grinding cost is seldom recognized as being sufficient to be worth correcting. For these reasons one may be lead to the erroneous conclusion that slow-speed operation is only occasionally applicable. The effect of mill speed on grinding efficiency has been studied in laboratory tests."! The results of some of these tests are given in tables I and I1 and fig. 1. In these tabulations, batch tests using ore charges of 125 to 200 lb were considered comparable to high pulp-level operation and charges of 50 to 100 lb comparable to low pulp-level operation. For the high pulp-level operation, these tests indicate the existence of a maximum in efficiency for operation at a speed of 50 pct of critical, both for the soft (dolomite) and hard (chert) ore. In low pulp-level operation, a decrease in speed increases the efficiency of grinding dolomite; no maximum of efficiency appears in the range of speeds tested. The results with chert were inconclusive. If the performance of large mills is indicated

Jan 1, 1951

By Harlowe Hardinge, R. C. Ferguson

Laboratory and plant data covering 12 different operations show that lower than "standard" ball mill speeds increase grinding efficiency. In the case of high pulp-level mills, the gain is so great that the increase in capital cost of the larger lower speed mill will pay for itself in less than a year's time. THE object of this paper is to show the economic advantage of operating ball mills at relatively slow speeds. Although many operators know that grinding costs are reduced by operating mills at low speeds, they seldom do so for a variety of reasons. When capital is limited, first cost is of primary importance, and installation of the less costly, highspeed mill is favored. When materials are in short supply, as during a war period, capacity rather than economy is the primary consideration. Existing mills are then speeded up to provide the desired increase in capacity, and new mills are purchased without consideration of maximum grinding efficiency. When the mill speed is increased to secure more production, the increase in grinding costs is often obscured by the total benefit derived from the additional output. This increase in grinding cost is seldom recognized as being sufficient to be worth correcting. For these reasons one may be lead to the erroneous conclusion that slow-speed operation is only occasionally applicable. The effect of mill speed on grinding efficiency has been studied in laboratory tests."! The results of some of these tests are given in tables I and I1 and fig. 1. In these tabulations, batch tests using ore charges of 125 to 200 lb were considered comparable to high pulp-level operation and charges of 50 to 100 lb comparable to low pulp-level operation. For the high pulp-level operation, these tests indicate the existence of a maximum in efficiency for operation at a speed of 50 pct of critical, both for the soft (dolomite) and hard (chert) ore. In low pulp-level operation, a decrease in speed increases the efficiency of grinding dolomite; no maximum of efficiency appears in the range of speeds tested. The results with chert were inconclusive. If the performance of large mills is indicated

Jan 1, 1951

By Henry N. McCarl

[The Construction Materials section contains the following Chapters: Aggregates Cement and Cement Raw Materials Crushed Stone Dimension and Cut Stone Lightweight Aggregates Gypsum and Anhydrite Sand and Gravel Insulating Materials-Thermal and Sound Slag Roofing Granules] Mineral aggregates are those natural and manufactured industrial mineral and rock materials that provide bulk and strength in portland 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 aggregate materials. The per-ton value of mineral aggregate materials at the production plant in 1980 and 1981 varied from $2 to $5 for most sand and gravel and crushed stone, $3 to $6 for air-cooled slag, $7 to $20 for expanded slag and expanded clay or shale aggregate, to as much as $165 to $320 for expanded perlite or vermiculite. The expanded lightweight aggregates have been dramatically affected by increasing fuel costs. It is ironic that the specialized aggregates used as insulating materials to conserve energy cost so much more to produce due to the high proportion of energy consumed in their production. The first four parts of "Construction Materials" deal with the utilization of four major mineral aggregate types: Crushed Stone, Lightweight 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 not discussed in the Commodity section of this book.

Jan 1, 1983

By Harry M. Mikami

Refractories are heat-resistant, generally nonmetallic materials used as the linings of furnaces or high temperature vessels in the steel, iron, nonferrous metals, glass, cement, lime, ceramic, chemical, petroleum, paper, and power and heat generation industries. Refractories must have structural strength at high temperatures but also, in many applications, must simultaneously resist chemical-physical corrosion-erosion from stags, metals, granular solids, or gases. Among the major uses are the pyrometallurgical processes for producing iron, steel, copper, aluminum, nickel, lead, zinc, etc. Rotary cement kilns, glass tanks, refineries, utility boilers, chemical and ceramic (including refractories) plants, and a myriad of other smaller scale users employ refractories in the high temperature parts of their operations. Thermal, chemical, and structural conditions under which refractories are used differ widely so there is a great variety of refractories to fill the various needs. Two major classifications are the "basic" and "acid" types. Basic refractories include magnesia and chromite, singly and in combinations, dolomite, and forsterite (olivine). The acid category includes aluminosilicates, alumina, and silica. There are a number of other specialized types such as carbon, graphite, silicon carbide, zircon, and zirconia that have important applications but are used in much smaller amounts than the major categories. Physically, refractories can be divided into bricks and shaped products on the one hand and unshaped or monolithic products (also termed specialties) on the other. There are many further subclassifications and divisions, a discussion of which is beyond the scope of this chapter; see Refs. 2 and 9. Raw materials for the principal basic refractories are magnesia and chrome ore. Magnesia, generally termed magnesite or periclase, is obtained mainly from seawater or saline brines extraction, but substantial amounts are produced from mined magnesite (MgCO3). Dolomite (CaCO3•MgCO3), another important basic refractory, is obtained entirely from mined sources. Acid refractory raw materials are: fire clays, flint clays, kaolin, and other natural clay minerals; aluminosilicate minerals such as kyanite, andalusite, sillimanite, pyrophyllite, bauxitic clays; calcined refractory grade bauxite, alumina from the Bayer process for the alumina group; and quartzitic rocks for silica refractories. The total value of all refractories shipped in the United States in 1974 was $989 million, a record to that date. Of this amount, about 73% represents bricks and shaped products and 27% is in nonshaped or monolithic products which comprise mortars, cements, castables, plastics, and ramming and gunning mixes. Fig. 15.4E.1 shows the rising value of all U.S. refractory shipments in the period 1948-1974. Values of brick and shapes paralleled

Jan 1, 1976

By H. E. Stauss, E. I. Salkovitz, F. W. von Batchelder

EXISTING information regarding the structure of a spherulite in nodular cast iron is based on optical studies. According to these data, a nodule consists of an aggregate of graphite crystallites radiating from the center, with the closely packed basal planes at right angles to the radii. The c axes lie along the radii. This view faces some uncertainty in the fact that the c axis does not represent the accepted direction of fastest growth in graphite. To supplement the optical information, X-ray studies have now been made. The principle used was to screen the nodule in greater part from the X-ray beam and expose only a minor cap. As successively larger portions of the nodule were introduced into the X-ray beam, any differences in the X-ray patterns could be observed. Such photographs have been taken with chromium radiation and a Laue camera. The graphite nodule itself, about 0.010 to 0.025 in. in diam, was mounted with vaseline on a micrometer screw for control of the linear motion. The nodule rotated about 45" each time that it was translated linearly. The nodules were obtained from magnesium-treated hypereutectic iron by electrolytic solution of the iron in hydrochloric acid. In Fig. la is shown the pattern of the thinnest cap examined. In Fig. lb is shown the pattern of the same nodule moved 0.003 in. farther into the X-ray beam, and rotated 45" at the same time. Figs, la and lb indicate incomplete circles for graphite (the two outer circles arise from graphite) with the side arcs much weaker than the top and bottom ones. The arcs obtained are themselves not continuous in intensity but vary with maxima of intensity some 15" and 30" apart. The structure of the nodule that would give rise to such a pattern can be explained as follows. Basically the nodule consisted of small crystallites. The discontinuous character of the diffraction rings demonstrates that the nodule was not composed of randomly oriented crystallites. The strong vertical reflections and the weak lateral reflections show that the reflecting planes were roughly normal to the radii. The absence of sharp reflection spots suggests that the nodule did not contain large crystals. The sharpness of the diffraction rings in their radial direction shows that the variations in intensity along the arcs were not the result of line broadening resulting from extremely small crystals. In the diffraction patterns two rings corresponding to graphite were found. The third and inner ring in the figures originated in the vaseline. The graphite rings correspond to the a and ß lines reflected from the basal planes, showing that the radii of the nodules are the [0001] direction normal to the basal planes of graphite. The picture of the structure that is formed is, therefore, one of aggregates of crystallites. Within each aggregate the c axes of the crystallites tend to align themselves in the radial direction of the nodule, although these axes deviate somewhat in direction by a continuous variation of angle. Correspondingly the basal planes of the graphite crystallites are generally normal to the radii. It is a pleasure to acknowledge the assistance of M. C. Bloom and R. P. Dunphy of this laboratory.

Jan 1, 1952

By D. H. Forbes, H. M. Manasevit, F. L. Morritz

Single-crystal thin films of molybdenum have been grown. by the pyrolytic decomposition of molybdenum hexafluoride in a hydrogen ambient on various insulating substrates at temperatures front 650° to 900° C. Single-crystal discs of various orientations of magnesium aluminate spinel, a aluminum oxide, magnesium oxide, and the natural facets of beryllium oxide were all observed to exert epitaxial control on the depositing film. Determinations of the crystallographic relationships existing between film and substrates have been made, using X-ray diffraction three-circle goniometry and Laue back-reflection techniques. Using these data, crystallographic overlays have been constructed which suggest a possible interfacial geometry on the basis of a match between metal deposit atoms and metal ion sites in the substrate. A continuing program has been in effect in the Auto-netics Laboratories over the past several years aimed at the development of electronic materials in new and useful forms using chemical vapor deposition techniques. During the course of these investigations, the epitaxy of silicon1"5 and tungstenep7 on single-crystal metal oxide insulators was studied extensively. The deposition of molybdenum is a logical extension of the tungsten work since the crystal structure is identical and the lattice dimensions differ by less than 1 pct. The pyrolytic decomposition of molybdenum hexafluoride in hydrogen was used to grow molybdenum films on the oxide substrates AlzOs, MgA1~04, MgO, and Be0 at from 650" to 900°C, depending on the substrate material. Under the experimental conditions to be described, monocrystalline films of controlled orientation were obtained. The materials investigated and their crystal structure are listed in Table I. EXPERIMENTAL The molybdenum depositions were effected by the hydrogen reduction of molybdenum hexafluoride (MoFe) in a flowing system of hydrogen at atmospheric pressure. The schematic of the apparatus is shown in Fig. 1. The hydrogen, purified by passage through a heated palladium thimble, was mixed with the vapor of the liquid MoFe maintained in a steel bottle at room temperature (25°C). The mixture was passed over the substrate, which was heated by rf induction of a sup-

Jan 1, 1969

By G. B. Gould

FROM the very inception of the price-control experiment in the bituminous-coal industry, the problem of price differentials was of major importance. In fact, assuming that there will be no legal or Govern- mental obstacles to price control, the successful maintenance of the present or any other method designed to control bituminous-coal prices will depend upon the discovery of some satisfactory way to determine these differentials in price, among: individual mines and groups of mines. Being of organic origin, bituminous coal is a commodity that presents an almost infinite variety of qualities. It is inevitable, therefore, that a work- able price-control system must attempt

Jan 1, 1935

In cooperation with the United States Bureau of Mines and the Idaho Bureau of Mines and Geology, the University of Idaho offers in the School of Mines a number of fellowships. These fellowships are open to college graduates who have had good training in mining, metallurgy, or chemistry, and who are qualified to undertake research work. The income of each fellowship is $720 a year for the 12 mo. beginning July 1, 1919. Fellows will register as students in the University of Idaho and become candidates for the degree of Master of Science in Mining or Metallurgy (unless this or an equivalent degree has been earned). Their class work-will he directed by the heads of the departments of instruction, but the greater portion of their time will be spent in research work under the direction of the Bureau of Mines staff resident at the University. The purpose f this work is to undertake the solution of definite problems confronting the mining and metallurgical industries of the State of Idaho. For 1919-20 the following subjects are being considered: 1. Flotation-with especial reference to differential separation of various minerals. 2. Availability of western wood oils for flotation purposes. 3. Treatment of the complex gold-silver ores of southern Idaho. 4. Ore-dressing problems. 5. Mining problems. Applications, with certified copy of collegiate record, statement of professional experience, and names and address of three references, should be addressed to The Dean. School of Mines. Moscow Idaho_

Jan 6, 1919

By F. O. Willhofft

The symposium on mine safety held in connection with the annual meeting of the Institute three years ago, it. was pointed out that "at present no convenient, reliable, accurate means for determining the gas content of mine air is available, for use by the ordinary mine man." In a letter addressed to Coal Age and published on Feb. 25, 1925, Thomas T. Read, then Director of the Safety Service of the Bureau of Mines, stated: "It is to be hoped that sometime in the near future some-one will invent a reliable methane indicator that is con-venient to, use and will permit the keeping of all flames of every character out of bituminous mines, through doing away with the safety lamp." The Martienssen methane detector, which has re-cently received the official approval of the Bureau of Mines, is intended to. meet the demand for such an in-strument as expressed at that meeting and on many other occasions. The characteristics which qualify it for the task are the following: (1) simplicity; (2) small bulk and light weight; (3) ruggedness; (4) accuracy sufficient for the requirements; (5) safety; and (6) dependability. The principle on which the working of the instrument is based may best be explained by giving a brief out-line of the various stages of development through which the inventor, Professor Martienssen of the University of Kiel, Germany, advanced to the final solution of the problem which he had undertaken to solve.

Jan 2, 1928

By R. C. FLEMING

G OLD MINING is enjoying a real revival in the West, and a considerable portion of the production is coming from small properties. The large mining companies of the world get most of the publicity, but in the last year the small gold property has often proved a more attractive field for the mining engineer looking for something to do. Old mines have been re- opened, prospects have been more closely examined, and many properties that were out of the running with the high commodity and labor costs of two or three years ago, have recently been making money for their operators. An interesting phase of this activity is the operation of so-called one-man mines. The west is dotted with these small properties, without the resources or reserves to warrant large-scale operation, but which return a living and often something over to one or two men who under- stand mining and simple methods of treatment.

Jan 1, 1932

By Richard J. Lund

Stock piling-and by that I mean well-organized stock piling on a substantial scale-is almost as old as the hills themselves. It was back in early Biblical times, as recounted in the Book of Genesis, that Joseph was charged by Pharaoh with the responsibility of stock piling food during the seven years of plenty to guard against the seven subsequent years of famine that were revealed by the Pharaoh's dream. And this same policy of storing up food or materials to provide for future anticipated emergencies can be traced repeatedly down through the ages. So our own efforts are anything but new. Our modern concept of stock piling-the purchase and storage of strategic materials to assure supplies needed in time of some future war- stems from our experience in World War I. In 1920, the War Department was charged by Congress with the responsibility of procuring all War Department supplies and mobilizing industry in the event of another war. During the two decades that followed there were many authoritative studies made of our deficient mineral problem, all of which pointed out the urgent necessity of stock piling certain strategic materials as a reserve against future war. One such study, made in 1925 through the combined efforts of the Mining and Metallurgical Society and the AIME, was done at the ex- press request of the War Department. Eight years later another more de-

Jan 1, 1949

By B. H. Kear, S. M. Copley

Stress-stvain curves are presented for Ni3Al (y') cvystals in several ovientations, deformed in tension and compression at constant displacement rate, at temperatures from 70° to 2000°F. Both the yield stress and wovk havdening increase with temperature, with the magnilude of the effect dependent on ovientation. The yield stress maximum occurs at 1500°F in [001], at 1400°F in [011], and at 1200°F in [111]. The suppression of the yield stress peak in [011] and [111] orientatiorzs is due to the onset of cube slip, rather than octahedval slip, a1 elerated temperatures. The temperature and orientalion dependence of work hardening in nominal single slip orientations corvelates with changes in the CRSS ratio for octahedral slip and cube slip, in agreement with a model for work hardening based on pinning of screw dislocalions by cross slip from an octahedral plane into a cube plane. It is concluded that the unique plastic properties of y' have a decisive influence on both ductility and strength characleristics of y +y' nickel-base superalloys. It has long been recognized that the strength of y + y' nickel-base superalloys depends on the precipitation of the y' phase [basically Ni3(Al,Ti)]. This paper presents new data on the strength characteristics of single crystals of simple y' (Ni3Al), and forms the first step in a systematic program aimed at elucidating the mechanisms of hardening in the complex commercial alloys. 1) EXPERIMENTAL PROCEDURE Single crystals of off-stoichiometric NiA1 were grown from the melt under vacuum by a modified Bridgman method. The melt was poured into a preheated alumina mold and crystal growth was promoted from one end by gradient cooling. The crystals were homogenized by annealing in hydrogen at 2400° F for 72 hr followed by furnace cooling. Chemical analysis of samples taken from several crystals gave an average composition of 88.2 wt pct Ni. Spectrographic analysis gave as the principal impurities in weight percent— Si (0.02), Mg (0.01), Fe (0.02), Ti (0.002), Cu (0.008), and Co (0.03). Tensile specimens with specifications as in Fig. 1 were prepared by a series of operations involving electrical discharge machining, precision grinding, and electropolishing. Compression specimens with dimensions 1/4 by 1/4 by -3/4 in. were prepared in a similar manner, except for the initial shaping operation using a precision cut-off wheel/two-circle goniometer unit to give selected crystal orientations. Specimens were deformed in a Baldwin-Wiedemann testing machine with furnace attachment, using a strain rate of 5 x 10-4 sec-1. The strain measuring device consisted of extension arms attached to the tensile grips (or compression plattens) at one end and leading out of the furnace to an LVDT at the other. Temperature was controlled by a thermocouple placed in contact with the specimen. According to the known phase diagram for the Ni/A1 system,' when an alloy of the specified composition is cooled from the melt, primary y (nickel solid solution) dendrites grow at the expense of the liquid phase, which becomes enriched in aluminum. At the eutectic composition the remaining liquid freezes as a two-phase mixture of y + y' (Ni3Al). Upon further cooling, a solid state transformation occurs, involving the precipitation of y' in the primary dendrites, and the complete transformation of the eutectic mixture to massive y'. The as-cast structure consists, therefore, of y + y' dendrites with interdendritic regions of massive y', i.e., transformed eutectic, Fig. 2. 2) DISCUSSION OF RESULTS 2.1) Stress-Strain Curves. Fig. 3 shows tensile stress-strain curves for crystals in orientations close to [001] deformed at temperatures from 70° to 2000°F. Both the yield stress and total elongation are strongly temperature-dependent. At 70°F, easy glide is absent, and the work hardening coefficient BIT - G/300. At T > 1500°F, the negative slope of the stress-strain curves is due to pronounced necking in the crystals. The yield stress maximum at 1500° F corresponds with a minimum in the ductility, Fig. 4. The extensive duc-

Jan 1, 1968

By J. F. Myers, F. M. Lewis

C. G. McLACHLAN*-I have read this paper with considerable interest and wish to congratulate the authors on the care with which they carried out their experiments and for the detailed sizing data they have presented. 011 the other hand I do not feel that these data establish their contention that "with other factors the same, the work accomplished in a fine crushing rod mill is directly proportional to the rotating speed." My reason for making this statement is that their conclusion is based on the percentage of minus 65 mesh material produced at each of the speeds at which their tests were run. The rod mill is, however, not a fine grinding machine and therefore figures based on minus 65 mesh production are figures outside the range at which it operates to best advantage. Further, if rod mill performance is to be judged on the production of such material it should have been established that a rod mill will produce it as effectively as a ball mill. To check this last point I have gone over some of the rod and ball mill grind-ing figures for our Waite-Atnulet operation and find that the ball mill at that property produces more minus 65 mesh material per horsepower than the rod mill. Moreover, this comparison is even more favorable to the ball mill if it is limited to minus 100 mesh production. It therefore seems to me that the most satisfactory basis on which to try to com-pare the performance of the rod mill in the present case is by taking a weighted average of all the new surface produced per horsepower. W. H. Coghill3 has published data which can be applied to the sizing figures presented by the authors, and if this is done the units of new surface per horsepower produced in the Tennessee tests are as follows: Admittedly the increment of increase in new surface per horsepower shown in the foregoing figures is not great, but its trend is nevertheless definitely in favor of slower speed operation, for the conditions under which these particular tests were run. I also feel that some information regarding liner contour should have been given as I think it will be found that a mill which is equipped with liners which lift the rod load can be run at a slower speed than a mill in which the liners are comparatively smooth. J. F. MYERS and F. M. LEWIS (authors' reply)—The position taken by Mr. McLachlan is to be respected even though we are all aware of the faults of surface considerations. As he points out. the increment of increase is very small. It is so small in fact that for all practical purposes it does not conflict with the conclusions of the paper. The authors appreciate Mr. McLachlan's comprehensive study of the data.

Jan 1, 1950