Search Documents

By Stanley Kesler

The first of two initial 650-mw units of the Paradise Steam Station, located on the banks of the Green River in the south-central portion of the western Kentucky coal basin, is scheduled for operation in late fall of 1962. This plant will be the eighth large-capacity, modern station built by TVA in a series starting with Johnsonville, operated first in 1951. During the subsequent ten years, unit sizes have increased from a capability of 125 mw to 650 mw at Paradise. This new unit will take its place in a power system that serves an area of about 80,000 sq miles with a present installed capacity of over 12,000 mw. Upon completion of the Paradise units and other additional hydro and steam units presently under construction, the system capacity will have reached over 15,000 mw. Projected load estimates indicate that this system will provide a margin of slightly under 10% of dependable capacity above peak demand at that time. One Paradise 650-mw unit at that time will represent approximately 4yc of the total system installed capacity.

Jan 10, 1962

By F. H. Rhines, A. H. Grobe

The constitution of the indium-zinc alloy series has been investigated by Wilson and Peretti,1 who determined the liquidus and eutectic temperatures by the conven-tional method of cooling curves and the eutectic composition by analyzing eutectic exudations. Recent developments affecting the availability of indium and consequent increased interest in its applications make a more complete knowledge of the constitu- tion of its alloys desirable. As a part of a program far the reexamination of the constitution of indium alloys by precision methods, the indium-zinc phase diagram (Figs. I and 2) has been redetermined in its entirety. The eutectic temperature (I43. 5°C.) reported by Wilson and Peretti has been confirmed exactly, but their value of the zinc concentration at the eutectic, 4 per cent, was found to be high; the new value is 2.8 per cent of zinc. There is also a rather large difference between the forms of the liquidus curves of Wilson and Peretti and those found in the present studies. The solidus curves herein have been located for the first time and the limits of solid solubility have been tenta-

Jan 1, 1944

By A. H. Grobe, F. H. Rhines

The constitution of the indium-zinc alloy series has been investigated by Wilson and Peretti,1 who determined the liquidus and eutectic temperatures by the conven-tional method of cooling curves and the eutectic composition by analyzing eutectic exudations. Recent developments affecting the availability of indium and consequent increased interest in its applications make a more complete knowledge of the constitu- tion of its alloys desirable. As a part of a program far the reexamination of the constitution of indium alloys by precision methods, the indium-zinc phase diagram (Figs. I and 2) has been redetermined in its entirety. The eutectic temperature (I43. 5°C.) reported by Wilson and Peretti has been confirmed exactly, but their value of the zinc concentration at the eutectic, 4 per cent, was found to be high; the new value is 2.8 per cent of zinc. There is also a rather large difference between the forms of the liquidus curves of Wilson and Peretti and those found in the present studies. The solidus curves herein have been located for the first time and the limits of solid solubility have been tenta-

Jan 1, 1944

By Walter Knox, Charles H. Sawyer

All of the coals commonly used in domestic bituminous stokers form coke, and satisfactory operation depends upon the fact that the coke formed is so weakly bound together that it breaks readily in the normal operation of the stoker and automatically maintains a good fuel bed. Some coals, because of their tendency to form solid, blocky coke, are practically excluded from use in small domestic stokers as now built. Other coals, some among the best stoker coals available, can form this troublesome coke under certain conditions. Many contradictory methods have been offered as cures for coke formation. Generally the procedure has been to try various adjustments until a combination was found that seemed to give better results. Such random methods of treatment have not provided any reliable information as to causes. The present paper covers a comprehensive test program undertaken by the Koppers Company's Stoker Coal Research Laboratory at Kearny, N. J. The program had two main objectives; first, to discover what factors affected coke formation, and second; to define corrective steps that could be applied in stoker service work. Conclusions and Results i. The design of the stoker outweighs in importance all other factors capable of improving coke formation. 2. Insufficient air supply aggravates the formation of large blocky coke, although raising the air above 30 to 40 per cent excess (as determined during steady running) does not further improve the character of the coke formed and only reduces its accumulation at the expense of efficiency, increased fly ash, poorer clinker-ing, and other disadvantages. 3. Increasing the coal feed results in a somewhat more friable coke structure and is recommended for persistently troublesome jobs. 4. Increasing over-fire draft improves the character of the coke formed and reduces troublesome accumulations by accelerating off-period burning, although at some expense in efficiency and some increase in fly-ash accumulation. 5. Coke structure was not substantially improved by blocking some of 'the retort tuyeres, although the blocking of tuyeres at the feed-screw end of a rectangular retort did lead to somewhat improved performance, possibly because of considerably better distribution of coke in the fuel bed. 6. With the equipment tested no difference was shown between installation of the same stoker in a steam boiler and a warm-air furnace, or between a sand-filled and a ventilated type of hearth. 7. The following design features had no noticeable effect on coke formation: a. Presence or absence of coal-tube air as provided by many manufacturers to eliminate smoke-back. B. Presence or absence of a flap damper ill the air duct to minimize off-period burning. c. Continuous or intermittent (ratchet and pawl driven) movement of fuel feed screw.

Jan 1, 1944

By Charles H. Sawyer, Walter Knox

All of the coals commonly used in domestic bituminous stokers form coke, and satisfactory operation depends upon the fact that the coke formed is so weakly bound together that it breaks readily in the normal operation of the stoker and automatically maintains a good fuel bed. Some coals, because of their tendency to form solid, blocky coke, are practically excluded from use in small domestic stokers as now built. Other coals, some among the best stoker coals available, can form this troublesome coke under certain conditions. Many contradictory methods have been offered as cures for coke formation. Generally the procedure has been to try various adjustments until a combination was found that seemed to give better results. Such random methods of treatment have not provided any reliable information as to causes. The present paper covers a comprehensive test program undertaken by the Koppers Company's Stoker Coal Research Laboratory at Kearny, N. J. The program had two main objectives; first, to discover what factors affected coke formation, and second; to define corrective steps that could be applied in stoker service work. Conclusions and Results i. The design of the stoker outweighs in importance all other factors capable of improving coke formation. 2. Insufficient air supply aggravates the formation of large blocky coke, although raising the air above 30 to 40 per cent excess (as determined during steady running) does not further improve the character of the coke formed and only reduces its accumulation at the expense of efficiency, increased fly ash, poorer clinker-ing, and other disadvantages. 3. Increasing the coal feed results in a somewhat more friable coke structure and is recommended for persistently troublesome jobs. 4. Increasing over-fire draft improves the character of the coke formed and reduces troublesome accumulations by accelerating off-period burning, although at some expense in efficiency and some increase in fly-ash accumulation. 5. Coke structure was not substantially improved by blocking some of 'the retort tuyeres, although the blocking of tuyeres at the feed-screw end of a rectangular retort did lead to somewhat improved performance, possibly because of considerably better distribution of coke in the fuel bed. 6. With the equipment tested no difference was shown between installation of the same stoker in a steam boiler and a warm-air furnace, or between a sand-filled and a ventilated type of hearth. 7. The following design features had no noticeable effect on coke formation: a. Presence or absence of coal-tube air as provided by many manufacturers to eliminate smoke-back. B. Presence or absence of a flap damper ill the air duct to minimize off-period burning. c. Continuous or intermittent (ratchet and pawl driven) movement of fuel feed screw.

Jan 1, 1944

On Feb. 16, 1948, the Board of Directors of AIME authorized the publishing of "Technical Notes" in METALS TECHNOLOGY. The purpose is to provide prompt publication of wry short items of the following general types: 1. Results of short investigations which do not warrant a paper. 2. The conclusions of extensive investigations of insufficient general interest to justify a regular paper. 3. Conclusions arising in the course of an investigation, which, because of interest to others in the field, the author wishes to present prior to completion of the investigation. 4. Pertinent factual comment (not mere argument) on the subject matter of previous "Notes." Such Notes will be subject to the approval of the Auxiliary and AIME Publications Committees, but can be handled more promptly than regular papers because they need not be referred to readers. The recommended maxi- mum length is 500 words; notes in excess of 1,000 words will not be considered for this type of publication. A graph or photograph may be included as part of the note when particularly illustrative. As with regular papers, contributions to the new section should be submitted to the Secretary of the AIME.

Jan 1, 1948

By F. C. Langenberg

It is the purpose of this paper to present a limited amount of experimental data obtained on the Charpy impact machine. Several concrete examples will be given showing the relation existing between the results obtained upon the Charpy impact machine and the behavior of the parts tested when in service. Although it is pointed out by G. Charpy and A. Cornu-Thenard1 that it is first necessary to determine a satisfactory working process before studying the correlation between the results of these tests and the behavior of the parts tested in service, this ideal course cannot be strictly adhered to. If a certain part repeatedly fails in service and the available tests give no indication of its cause, advantage must be taken of any possible means that will solve the problem; therefore, even though the reliability of the results obtained by the Charpy impact machine have been questioned by many, it was necessary to use this instrument without giving careful consideration to its possible sources of error. It would seem that the conclusions arrived at by Charpy -and Cornu-Thenard justify the assumption that the precision obtained by this machine is comparable to that obtained by the other more common forms of testing. The second general conclusion arrived at by them, namely, that the impact test upon notching does not offer any direct correlation to the ordinary tests, is also borne out by many hundred determinations made in the laboratories at Watertown Arsenal. This statement, however, should be qualified as follows: Other ordinary tests include the static tensile test from bars taken in a longitudinal direction and the Brinell hardness. The author agrees that no law is yet known for the computation of the energy absorbed in the rupture of bars of the same material but of different dimensions. Although Charpy and Cofnu-Thenard do not refer in their valuable article to the use of the Charpy machine in industrial practice, it should be stated that this instrument has been in constant use in the laboratory at Watertown Arsenal for several years, and is now employed for both routine and experimental testing.

Jan 1, 1920

By R. A. Foos

During the radium boom in the early part of the twentieth century, the basic chemistry of uranium was fairly well defined. Uranium production has progressed from the status of a radium by-product to a very important industry. With the ever increasing need for more efficient and cheaper methods of processing uranium ores, new techniques are being developed. Since uranium and vanadium often occur together in nature, the latter element will also be considered. As production rates, costs, and certain aspects of uranium chemistry are still classified by the Atomic Energy Commission, these will not be discussed. Domestic uranium deposits, in general, are composed of the minerals carnotite, which contains hexavalent uranium, and to a lesser extent, pitchblende and uraninite, which contain tetravalent uranium. Carnotite also usually contains vanadium. The uranium and vanadium contents of these ores vary considerably. The ores currently processed on the Colorado Plateau assay from 0.2 to 0.4 pct U and from trace amounts to 5.0 pct V. On the other hand, the phosphate rock deposits of the southeastern U. S., from which uranium is also recovered, contain only about 0.01 to 0.02 pct; processing of the

Sep 1, 1956

By Lovell Lawrence

MAGNETITE deposits in the Eastern States have been mined uninterruptedly since pre-Revolutionary War days. The industry, thriving in normal times, was given impetus in all periods of tumult, and continued to advance and expand, until the Lake Superior ores came into production. A period of comparative quiet existed until increased freight rates, together with increased mining costs on Lake Region ores, permitted the magnetites again to compete. This, coupled with World War demands, created unpre¬cedented activity. Producing plants were at their peak, new mines were equipped and put in operation and the industry pushed production beyond the absorption point. Ore stocks were tremendous, internal competition severe, and a great increase in import of European ores brought the industry to a low ebb in 1923.

Jan 1, 1933

By W Lindlief, Cyril Stanley Smith

Several investigators, mainly concerned with the mechanical properties of the alloys, have studied the so-called aluminum bronzes after various quenching and reheating treatments. Of these works, perhaps the most complete is that of Bouldoires, who studied changes of length, electrical conductivity, thermoelectric force, hardness and micro-structure on tempering quenched alloys containing 5 to 20 per cent of aluminum, although the work of Carpenter and Edwards,² Curry13 Greenwood,4 Braesco,5 Matsuda,67 Grard8 and others has added much to our knowledge of the changes occurring during tempering. The so-called acicular ß decomposes on tempering at temperatures between 350" C. and the eutectoid, giving rise to a Widmanstätten structure of a needles in a matrix of 6 or fine a + 6, associated with an increase in hardness and almost complete loss of ductility. Matsuda studied the eutectoid transformation by means of dilatation and electrical conductivity measurements during cooling at different rates. He found that on cooling at the rate of 10" C. per minute there was a decrease in electrical resistance and in length instead of the usual increase which occurred with slow rates of cooling. On tempering the rapidly cooled samples, the increase commenced at about 400" C. and at 520" C. the resistance and length had reached the equilibrium values. These peculiarities he accounted for as being due to a transitional phase ß' being formed, ß' having an electrical resistance and volume less than either ß or a + 6. Obinata9 published some electrical conductivity curves for copper-aluminum alloys showing a double break at the eutectoid temperature,

Jan 1, 1933

By Carl R. Christiansen

Since the first pay hole in Missouri's "New Lead Belt" was drilled in 1955, this district has become one of the world's leading sources of lead. The belt extends from north of Viburnum in a southerly direction to near Eminence, a distance of about 35 miles. The St. Joseph Lead Company was the discoverer and first to develop new mines in the Viburnum area. Since the discovery of the New Lead Belt, many companies have engaged in exploration programs and several major companies have become active in development of new mines. These include Cominco American, Inc., which operates a joint venture with Dresser Industries; Ozark Lead Company, a subsidiary of Kennecott Copper Company; and Missouri Lead Operating Company, a joint venture of Arnax and Homestake. St. Joseph Lead Company, with over 100 years of experience in the Old Lead Belt, has served as a leader in development of equipment and mining techniques, making its properties some of the most efficient mining operations in the world. The new producers give the district the benefit of fresh viewpoints, as their engineers are mostly from outside of Missouri and their previous experience has been considerably different from conventional lead belt practices. While all operations are similar in that they are room-and-pillar, the diverse experience of the operators has produced a group of mines that employ a variety of equipment and mining techniques to give increased efficiency

Jan 1, 1970

By John P. Goheen

Considerable work has been done in developing a pyrometer to measure the temperature of molten brasses, bronzes, and aluminum in the crucible. On account of the high melting points and the amount of zinc and sulfurous fumes given off from molten brasses, the conditions are somewhat severe for a thermocouple of standard design; but satisfactory results are obtained with a portable pyrometer, 3 ft. (0.9 m.) of connecting lead wire, and a special 5-ft. nickel-nickel chromium thermocouple, composed of rods 1/4in. (6.35 mm.) in diameter. The lower 12 or 24 in., as desired, may be made detachable so that new tips may be connected at little trouble or expense. The portable instrument need not be of the extreme high-resistance type, as the movable parts of the galvanometer of a lower resistance instrument may be better constxucted to withstand the continuous handling such an instrument receives. Platinum-platinum rhodium thermocouples, protected with porcelain and graphite tubes, have been used, but the lag in registering the temperature is too great. It has been found that the range of temperature for various brasses is as follows: Red brasses...............2200-2250" F. (1205-1234" C.) Yellow brasses............2250-2400" F. (1234-1318' C.) Bronzes..................2300-2550" F. (1260-1400" C.) A recent test with a portable pyrometer having a range of 2600" F. with a bare 1/4 in. heavy exposed couple 5 it. long and a handle attached at the upper end showed that the temperatures of molten aluminum under varying conditions in an oil-fired crucible furnace and one of the Simplex type were as follows: CRUCIBLE, OIL-FIRED FURNACE SIMPLEX FURNACE Temperature of metal in furnace....... 1540" F. (837" C.) 1530" F. (834" C.) Temperature in ladle after skimming at furnace......................... 1480" F. (805" C.) 1440" F. (784" C.) Temperature in ladle after skimming at floor near mold................... 1440" F. (784" C.) 1430' F. (778" C.)

Jan 1, 1923

By John P. Goheen

Considerable work has been done in developing a pyrometer to measure the temperature of molten brasses, bronzes, and aluminum in the crucible. On account of the high melting points and the amount of zinc and sulfurous fumes given off from molten brasses, the conditions are somewhat severe for a thermocouple of standard design; but satisfactory results are obtained with a portable pyrometer, 3 ft. (0.9 m.) of connecting lead wire, and a special 5-ft. nickel-nickel chromium thermocouple, composed of rods 1/4in. (6.35 mm.) in diameter. The lower 12 or 24 in., as desired, may be made detachable so that new tips may be connected at little trouble or expense. The portable instrument need not be of the extreme high-resistance type, as the movable parts of the galvanometer of a lower resistance instrument may be better constxucted to withstand the continuous handling such an instrument receives. Platinum-platinum rhodium thermocouples, protected with porcelain and graphite tubes, have been used, but the lag in registering the temperature is too great. It has been found that the range of temperature for various brasses is as follows: Red brasses...............2200-2250" F. (1205-1234" C.) Yellow brasses............2250-2400" F. (1234-1318' C.) Bronzes..................2300-2550" F. (1260-1400" C.) A recent test with a portable pyrometer having a range of 2600" F. with a bare 1/4 in. heavy exposed couple 5 it. long and a handle attached at the upper end showed that the temperatures of molten aluminum under varying conditions in an oil-fired crucible furnace and one of the Simplex type were as follows: CRUCIBLE, OIL-FIRED FURNACE SIMPLEX FURNACE Temperature of metal in furnace....... 1540" F. (837" C.) 1530" F. (834" C.) Temperature in ladle after skimming at furnace......................... 1480" F. (805" C.) 1440" F. (784" C.) Temperature in ladle after skimming at floor near mold................... 1440" F. (784" C.) 1430' F. (778" C.)

Jan 1, 1923

By R. E. Boni, G. Derge

Application of surface tension measurements has been made to molten silicates in order to determine the effect of sulphur upon the surface tensions of synthetic blast furnace slags. In melts with the same molar ratios of AI2O3 + SiO2 to the basic oxides BaO, CaO, and MgO, the surface tensions increase in the order of oxides listed. Sulphur lowers the surface tensions of the basic BaO, basic CaO, acid BaO, acid CaO, and acid MgO slags in that order; and the concentration of excess sulphur at the slag surface increases in this same order of slags. The rate and amount of desulphurization of iron by these slags is favored by a low excess surface sulphur in the slag. IN a previous paper,1 the authors discussed the applications of surface tension measurements of molten silicates to problems of metallurgical interest. Of major importance is the aid that such studies lend to forming a working concept of slag structure. Since the ability of a slag to desulphurize metal depends strongly upon its composition,2"4 fundamental information about the structural differences between various slags which contain sulphur should aid the development of better desulphurizing media. For that reason, the present investigation concerns the effect of sulphur upon the surface tensions of synthetic blast furnace slags. Experimental Procedure , The maximum bubble-pressure method was used to measure the surface tensions of synthetic blast furnace slags in the temperature range 1300° to 1600°C. The method is based upon the equation which was developed by Schrödinger5 from a consideration of the forces of hydrostatic pressure and surface tension of a liquid which oppose bubble formation when a gas is forced through a tube immersed in the liquid. where y is the surface tension between argon and slag in dynes per centimeter; g is the gravitational constant, centimeters per second2; H is the manometer reading in centimeters; s2 is the density of manometer fluid in grams per cubic centimeter; S1 is the density of the medium in grams per cubic

Jan 1, 1957

By A. T. Shurick

THE present economic crisis in bituminous coal is substantially the most insidious, and critical, in the modern history of the industry. The large consumption deficit that has gradually developed (almost unawares), has culminated in a situation that has forced home the urgent necessity for prompt and radical remedial measures, such as the various mergers now in course of negotiation. Conditions today are sufficiently comparable with those in the iron and steel industry, preceding the formation of the United States Steel Corpn., to suggest the possibility of a sweeping super-consolidation, that all but staggers the imagination. The important function of the banker in this, and lesser projects, is too well known to require comment, and it is important that we understand clearly just what these functions are. Certain features in banking practice came up for consideration in connection with a rather exhaustive economic study into the prospective future of the coal industry, upon which I was recently engaged for an Eastern bituminous interest. This survey was made for the purpose of effecting a decision on certain pressing questions of policy, involving considerable capital expenditures, that would be compatible with the flattening out in the curve of production in recent years. An examination of the TRANSACTIONS, and the coal literature generally, failed to disclose any pertinent, and authoritative data, on this subject. This was more or less characteristic of the whole survey, which had involved a large amount of original research, and measures were taken to procure the required information. The following notes have been compiled largely from the data thus collected, supplemented with material, suggestions and criticisms, by several of the larger banking houses active in coal, together with personal memoranda of my own.

Jan 1, 1928

By L. J. Gurevich

IN the course of the examination, at the Bureau of Standards, of fusible tin boiler plugs for the Steamboat Inspection Service, it became evident that an investigation should be undertaken to determine the precautions necessary in the manufacture of acceptable plugs. The results of the tests of these plugs show that their manufacture has improved, though at present not all of the plugs tested are satisfactory. Table 1 gives the result of tests of some 1500 plugs from about 100 makers. Records of the tests show that several of the makers were able to produce satisfactory plugs with every pouring. The Steamboat Inspection Service has the following specifications for fusible plugs: "Fusible plugs for use in boilers of steam vessels under the Jurisdiction of the Steamboat Inspection Service shall be made of bronze casing with the bore tapering continuously and openly from end to end, and filled from end to end with tin not less than 99.7 per cent. pure and to contain not more than 0.1 per cent. of lead and not more than 0.1 per cent. of zinc. The small end of the bore may be countersunk not more than 1/32 in. in depth and width, but no recess, thread, or cavity other than this countersink shall be allowed."

Jan 8, 1919

E. Hill, South Norwalk, Conn. (communication to the Secretary*) :—The phenomenon described by Dr. Ledoux, involving an apparently abnormal high temperature in the air-cylinders of compressors, has not been, so far as I know, discussed in technical literature. The common formula for the adiabatic compression of dry air does not account for heat suficient to flash ordinarily decent cylinder-oils, nor do the text-books include in their theoretical statements any quantitative consideration of the effect of leaks in the ideal machines which they contemplate. This lack I have endeavored to supply by preparing, in the form of a circular, for the use of the customers and correspondents of the Norwalk Iron-Works, a brief mathematical

Jan 1, 1904

By B. W. Adams, R. W. Shilling

9.4-1. Basic principles. DESCRIPTION AND BASIC FUNCTIONS. The concept of inclined skip haulage is not new. The basic idea has been in use at least 400 years. The system is essentially a steeply inclined railway utilizing a hoist to pull the skips to the top or intermediate positions. Inclined skip haulage is often justified where high lifts would require long hauls for other haulage systems. The basic system types are as follows: 1. Single skip, single drum. This system is a single car pulled by a simple hoist system. 2. Balanced skip, single drum. A system utilizing two cars (skips on cables)--one overwound, one underwound-on a single drum. The dead weight of one skip and cable balances the dead weight of the other. As one skip ascends the other descends between two fixed points. 3. Balanced skip, double drum. This system is an elaboration of system No. 2, except the drums may be disengaged from one another to permit the skips to service various loading and dumping points. The preceding are major classifications subject to numerous variations. These variations may be in the skipway, skip design, loading methods, or unloading methods. A few examples follow: 1. The skipway may be standard or special railroad, an overhead monorail or cable, or a ramp for rubber tired vehicles. 2. The skip, per se, may be of varying dumping arrangements (side, bottom, etc.) or could be the box of the vehicle hauling to the skip. 3. Loading may be accomplished directly from the service unit to skip, through an intermediate loading device (e.g., a pocket), or into bins which feed the skip. Loading may be at more than one point. 4. Unloading of the skip can be simple or complex as required. Dumping may be to the haulage unit, to bins and feeders, or to a crusher and conveyor system. Dumping may take place at more than one point.

Jan 1, 1968

By WM. E. Mlligan

IN the last year, much information had become available as to the extent that zinc participated in the war effort. The importance of foreign zinc in this program had been indicated by Bateman (M&M April 1945) as of the order of 400,000 tons annually in zinc or contained zinc. Pehrson (M&M April 1945) reviewed the domestic ore-reserve situation with respect to most minerals and metals and showed the extent to which commercial zinc ores had become depleted in this country. This picture was further darkened by O.P.A. figures appearing in E.&M.J. July 1945 in which figures for total production during the three previous years were broken down into percentages produced under ceiling and various quota price categories. True, factors other than depleted ore reserves contributed to this picture. Among the more important of these, were shortage and high cost of labor, both skilled and unskilled, and the general difficulty and cost of maintaining adequate equipment and supplies. The cost of production in the Tri-State district was most affected.

Jan 1, 1946

By F. V. Lenel, J. A. Dromsky

The influence of thermal and mechanical treatments upon the elevated-temperature stability, the microstructure, and the mechanical properties of aluminumaluminum oxide alloys is investigated. Compacts from atomized and flake aluminum powders were sintered at temperatures just below the melting point of aluminum in a vacuum of 10-4 Torr for several hours and were then hot-extruded. During this treatment the hydrated oxide present on the surface of the powder particles decomposes, the water vapor produced reacts with the aluminum forming additional oxide, and the hydrogen developed is removed by diffusion to the surface. Extrusions of compacts so treated are stable at temperatures up to the melting point of aluminum and do not form blisters and internal defects typical of extrusions from untreated powder. Electron micrographs of extrusions from unsintered compacts show long parallel oriented platelets typical of the IN previous investigations1,2 the properties and structure of aluminum alloys were described which had been produced by cold compacting aluminum powder and then hot pressing and extruding the compacts. Both the structure and the properties of these alloys differ significantly from those of commercially produced aluminum-aluminum oxide alloys. When commercial alloys are produced, they are given a sintering treatment in air at about 600°C between cold compacting and hot pressing.3 During this treatment the hydrated oxide, which forms the coating on the aluminum-powder particles from which the alloys are prepared, is decomposed.4 The chemically bound water which is released reacts with the aluminum and forms aluminum oxide and hydrogen. Most of the hydrogen is eliminated by hydrated oxide skins on the original powder particles, while the oxide particles in extrusions from sintered compacts are broken up. The strength of extrusions from treated powder is somewhat lower, but their ductility is considerably improved over that of extrusions from untreated powder. The slip-trace patterns on electron microgvaphs of extrusions which had been strained in tension before replication indicated that the grain size of the extruded alloys was approximately the same as that of the original powder particles. Coarse-grained alloys were produced by severe cold work and annealing of the extrusions. They have significantly lower room-temperature strength, but about the same ductility as the vacuum-sintered fine-grained alloys. The size and shape of oxides in the coarsegrained alloys is similar to those of the fine-grained alloys, but the particles are somewhat more uniformly distributed. diffusing to the interior or exterior surfaces of the compact, but it is difficult to eliminate all of it because the solubility of hydrogen in solid aluminum is very low even near its melting point. Extruded alloys which are not sintered before hot pressing and extrusion appear quite sound upon metallo-graphic examination, but develop severe surface blistering and internal fissuring when they are heated to elevated temperatures after extrusion. Fissures and blisters have been observed even in commercial alloys which had been sintered in air, although they are much less severe.' Because of the importance of this sintering treatment it was studied in this investigation in a modified form, using vacuum sintering rather than sintering in air, to insure more complete elimination of occluded hydrogen. The technique is described and the effect of the treatment upon the structure of the alloys is documented. It has been known for some time that extruded aluminum-aluminum oxide alloys are very finegrained, but an exact delineation of grains in electron micrographs has not been possible. In the conventional metallographic-etching techniques etchants attack the interface between the second-phase particles and the matrix in the alloys much

Jan 1, 1964