Search Documents

By PHILIP N. MOORE

THE problem of managing the policies of the Institute so that a middle course may be drawn between the close control of a few who are so situated that they can give continuing attention and intermittent control by occasionally present directors presentation .of the subject is to bring clearly before the membership of the Institute a summary of the attendance at the Directors' meetings for the past four years.

Jan 1, 1924

Falconbridge Nickel, the one-time subsidiary that grew up to swallow its own parent, Ventures Limited, in 1962, is not about to be left behind by rising nickel consumption. At a cost of several hundred million dollars, this Canadian firm has undertaken a series of new projects that will not only ensure its present share of the market, but also lead it into new areas of the nickel business. Although Falconbridge Nickel Mines Ltd. was not formed until 1928, it actually had its start in 1917- 18 with the discovery of a large, good grade nickel- copper deposit in Falconbridge, near Sudbury, Ontario. However, due to several factors, financing could not be obtained and the orebody lay fallow. It was not until 1928, when the Thayer Lindsley interests bought the property from the original owner, that it was developed.

Jan 10, 1968

By R. A. Hadfield

It seems a specially fitting opportunity to present a paper on the alloys of iron and aluminum at the New York meeting of this Institute, owing to the fact that America has, more than any other country, originated and developed the manufacture of cheap aluminum. The Cowles, Castner, and Hall systems have all originated in the ever-busy brain of our cousin across the water. The problem of cheaply producing this valuable metal has been a difficult one, but to the writer it seems that the more arduous the task the greater the delight with which our American friend attempts to overcome the difficulties surrounding it, and the more vim he throws into the work. Another and equally striking proof of this is to be found in the recent appearance of the already wellknown remarkable work, The Mefallurgy of Steel, by Mr. H. M. Howe, of the Institute of Technology, Boston, Mass. It is to be hopel that this Institute will not be slow to recognize by some special mark its appreciation of this signally valuable and original work. The writer has been led to describe the following experiments, believing that so far no full and exact report has yet been presented to this Institute as to the effect of aluminum alloyed or combined with the metal iron. It has been a special object to make the material as far as possible a true alloy or combination of aluminum and iron, with as small quantities as possible of other disturbing ingredients, such as silicon, manganese, etc. In the material described in these experiments, the total amounts of other elements present (sulphur and phosphorus being disregarded as present in such small quantities) do not exceed about 0.5 per cent. Such material may therefore be probably taken as fairly illustrative of the effect of the metal aluminum upon iron. Since completing the experiments the writer

Jan 1, 1891

By Donald B. Evans, Robert D. Pehlke

The solubility of nitrogen in liquid Fe-A1 alloys has been measured up to the solubility limit for formation of aluminum nitride using the Sieverts method. The activity coefficient of nitrogen decreases slightly with increasing aluminum content in the range of 0 to 4 wt pct Al. Based on a nitride composition, AlN, the standard free energy of formation of aluminum nitride from fhe elements dissolved in liquid iron has been determined to be: ?F" = -59,250 + 25.55 T in the range from 1600º to 1750ºC. The solubility of nitrogen in liquid iron alloys and the interaction of nitrogen with dissolved alloying elements in liquid iron have been the subject of a number of research investigations.' Most of this work, however, has been reported for concentrations well below those necessary for the formation of the alloy nitride phase. Data in the concentration region near the solubility limit of the alloy nitride, particularly for systems exhibiting stable nitrides, are important in evaluating the denitrifying power of various alloying elements. They are also useful in determining the stability of a given nitride if it is to be used as a refractory to contain liquid iron alloys. In view of the importance of aluminum as a deoxidizing agent in commercial steelmaking and the fact that its nitride, AIN, is a highly stable compound and has merited some consideration as an industrial refractory, the following investigation was undertaken. The use of the Sieverts technique provided a measurement of the equilibrium nitrogen solubility in liquid Fe-A1 alloys as a function of nitrogen gas pressure up to 3.85 wt pct A1 in the temperature range of 1600º to 1750°C. The values obtained by the Sieverts method were checked by means of a quenching method in which liquid iron was equilibrated with an A1N crucible under a known partial pressure of nitrogen gas, and the solubility of A1N in liquid iron determined by chemical analysis. EXPERIMENTAL PROCEDURE The theoretical considerations involved in determining the solubility product of a solid alloy nitride phase in liquid iron by measuring the point of departure of the nitrogen gas solubility from Sieverts law have been discussed by Rao and par lee.' The principal problem is to determine the variation of nitrogen solubility in an alloy as a function of the pressure of nitrogen gas over it with sufficient precision to establish the break point in the curve at the solubility limit of the alloy nitride phase. A fairly large number of data points are required to do this. A second problem is the determination of the composition of the precipitated solid nitride phase. This is necessary in order to define completely the thermodynamic relationships. The Sieverts apparatus used to make the nitrogen solubility measurements in this investigation is of essentially the same design as that described by Pehlke and E1liott.l The charge materials were Ferrovac-E high purity iron supplied by Crucible Steel Co. and 99.99+ pct pure aluminum. Recrystal-lized alumina crucibles were used, and were not attacked by the liquid alloys. The hot volume of the system which was measured for each melt ranged from 46 to 50 standard cu cm and was found to decrease linearly with decreasing pressure and with increasing temperature. The temperature coefficient of the hot volume at 1 atm pressure of argon gas was essentially constant for all experiments at a value of -6 X 10-3 cu cm per "C. The melt temperature was measured with a Leeds and Northrup disappearing filament type optical pyrometer sighted vertically downward on the center of the melt surface. The temperature scale was calibrated against the observed melting point of pure iron taken as 1536°C. The emissivity of all melts was assumed to be that of pure iron, taken as 0.43. The charge weights ranged from 110 to 140 g and the range of aluminum contents covered was from 0 to 3.85 wt pct. Aluminum additions were made as 12 to 15 wt pct A1-Fe master alloys previously prepared in the system under purified argon. The compositions of the master alloys were checked by chemical analysis and found to be in agreement with the charge analyses. Vertical cross sections of the master-alloy ingots were used as charge material for the equilibrations in order to minimize the effect of any segregation which might have occurred during solidification of the master alloys. Determinations of the solubility product of

Jan 1, 1964

IN speaking, on the subject, "Engineer-Citizens," at the Lehigh Valley Mineral Industries Conference dinner, on April 26, at Easton, Pa., George Otis Smith, Director of the United States Geological Survey and President of the American Institute of Mining and Metallurgical Engineers, said in part: "It would be carrying coke to Connellsville to bring to the Lehigh Valley the idea that mineral resources are the foundation of national prosperity. Unfortu-nately, however, this obvious, fact is not everywhere recognized. Too many of our economists, journalists, statesmen and other dopesters of present business con-ditions stress the human factor so strongly that they overlook the material with which men work out their destiny. To them the financial psychology of Wall Street and the political logic of Capitol Hill and the business commonplaces of Main Street all loom far larger than the geology of the Lehigh Valley or the engineering triumphs of Bethlehem, or, the creative thinking at Lehigh and Lafayette. "The present situation in the industrial and .business world is a complex of interacting causes and reacting effects not easily itemized and entered on our trial balance sheet. But, chief among the liabilities of today is the excess of production capacity in most branches of industry. The farmer has no. monopoly in his desire for relief. Whether your professional connections are with steel or cement, coal or oil, copper, or zinc, you; know too well that for, the moment America is over-engined, and you keenly realize the ever-present hazard of industry speeding up regardless of the curves or grades just around the corner.

Jan 5, 1928

By James F. Kemp

Discussion of the paper of D. Foster Hewett, Bulletin To. 27, March, 1909, pp. 291 to 310. JAMES F. KEMP, New York, N. Y.:-Mr. Hewett's paper is one of exceptional interest, because it not only adds an important contribution regarding one of the rarer, valuable elements, but also because it introduces compounds hitherto unknown and in associations no less novel. While we have occasionally dis¬covered and recorded asphaltite in metalliferous deposits, for example in the Joplin and Granby districts, we have not seen a metallic ore in a deposit essentially asphaltite. The source and method of introduction afford a subject well worth serious reflection. Vanadium was first discovered and recognized as a distinct element in the slags obtained in smelting the titaniferous magnetites at Taberg, Sweden. For a long time, therefore, we looked upon the titaniferous magnetites as its hone. Analyses proved, years ago, that it was present in the ores of this type in New Jersey and in the Adirondacks. It was quite rarely determined, but when looked for it was, I think, invariably found, although the Amount seldom exceeded 0.5 per cent. of V,05., In just what combination it exists in the titaniferous ores is uncertain. One might imagine V2O3 replacing some of the Fe2O3 of magnetite; or, since in the lead series vanadates and phosphates are closely akin, one might wonder if a lime-vanadate could take the place of apatite. Yet no lime-vanadate has been found in nature, and apatite itself is usually rare in the titaniferous ores. When percentage-curves are plotted for a series of analyses of the ores, the line of vanadic oxide shows a curious sympathetic behavior with the line of chromic oxide;' but the data are somewhat limited, and no compound has sug¬gested itself which throws light on the matter. Dr. W. F. Hillebrand has discussed the occurrence and dis-

Oct 1, 1909

By A. S. Bower

Any process which has for its object the preservation of iron and steel from rust, and which will make these metals more applicable than they now are to the requirements of mankind, will be sure to meet with attention from members of this association, and from all those who are either engaged in the extraction of the ore, its reduction to metal, or the subsequent application of the metal itself. It is, perhaps, not too much to say that when iron and steel are rendered secure against corrosion and decay, they will be used to an indefinitely greater extent than they now are. The whole realm of science has, therefore, been explored in the attempt to discover some method by which the formed article may be preserved, leaving its strength undiminished by the destructive action of rust. Paints, oils, varnishes, glazes, enamels, galvanizing, electro-depositing and what is called "inoxidizing" are among the many systems now in vogue to effect the preservation of iron and steel from the corrosive action of air and water. The object of this paper is to show what may he done in protecting iron and steel from rust by forming upon their surfaces a film of magnetic oxide by an inexpensive process. It is no new thing to be told that magnetic oxide of iron is unaffected by exposure to the atmosphere or to salt water for any length of time. The black sand of Taranaki, in New Zealand, is a sufficiently good example of this. Dr. Percy has pointed out that the reason why Russian sheet iron is less affected by exposure than ordinary sheet iron is because of a coating of magnetic oxide; but this was not known

Jan 1, 1883

By J. E. Brantly

In October 1939, a drilling program was commenced on the Atlantic seaboard of Brazil, with three steam rotary rigs of medium capacity. One of these was assigned to the State of Alagbas and the other two to the State of Bahia. During the remaining few months of 1939 and during the year 1940, some eight wells were drilled, two in Alagbas and six in Bahia. Two small producers were found in the latter state. In early 1941 three medium-weight Diesel rigs were added to the equipment, thus permitting the drilling of some 15 wells during the year 1941. The two small producers found in 1940 in the State of Rahia were near the city of Silo Salvador. In 1941 three additional small wells were brought in, in the same area, and a further producer on an isolated structure some 75 km. to the northwest of this production. No commercial production has been found in the State of Alagbas. Approximately 26 wells have been drilled or are drilling, six of which are producers— five in one area and one in another. The program for 1942 calls for the development of the two areas in which wells have been found and also the drilling of several wildcat structures located either by geophysics or surface geology. All production in the area of the several producing wells is somewhat less than 2000 ft. and in the other area about 3800 ft. The area of the several wells is known as the Lobato field, and is practically within the city limits of Sao Salvador. The area 75 km. northwest of the city will be known as the Candeias field.

Jan 1, 1942

By J. E. Brantly

In October 1939, a drilling program was commenced on the Atlantic seaboard of Brazil, with three steam rotary rigs of medium capacity. One of these was assigned to the State of Alagbas and the other two to the State of Bahia. During the remaining few months of 1939 and during the year 1940, some eight wells were drilled, two in Alagbas and six in Bahia. Two small producers were found in the latter state. In early 1941 three medium-weight Diesel rigs were added to the equipment, thus permitting the drilling of some 15 wells during the year 1941. The two small producers found in 1940 in the State of Rahia were near the city of Silo Salvador. In 1941 three additional small wells were brought in, in the same area, and a further producer on an isolated structure some 75 km. to the northwest of this production. No commercial production has been found in the State of Alagbas. Approximately 26 wells have been drilled or are drilling, six of which are producers— five in one area and one in another. The program for 1942 calls for the development of the two areas in which wells have been found and also the drilling of several wildcat structures located either by geophysics or surface geology. All production in the area of the several producing wells is somewhat less than 2000 ft. and in the other area about 3800 ft. The area of the several wells is known as the Lobato field, and is practically within the city limits of Sao Salvador. The area 75 km. northwest of the city will be known as the Candeias field.

Jan 1, 1942

By H. Vincent Wallace

ALTHOUGH it is universally accepted that free oxygen is A necessary in a cyanide solution for the dissolution of gold and silver-in accordance with Elsner's equation that 2Au + 4KCN + 0 + H20 = 2KAu (CN), + 2KOH- little has been written and insufficient attention paid to the drop in extraction due apparently to loss of dissolved oxygen in mill solutions. Aeration or oxygenation of cyanide solutions has been more or less successfully accomplished by various types of agitators such as the Dorr (with or without air lifts), Pachuca tanks and more recently "Turbo-mixers" and Denver "Super- agitators"; also by the introduction of chemical oxidizing agents such as Solozone (Na,O,) . At the Wright-Hargreaves and other mines in the Kirkland Lake camp, the introduction of this reagent at the rate of about 1.25 oz. per ton of ore applied to the feed of the ball mills has certainly been beneficial.

Jan 1, 1932

By Allan Martin, R. A. Swalin

Diffusion rates of manganese, aluminum, titanium, and tungsten in nickel were measured at temperatures between 1100° and 1300°C. Activation energies, Q, and values of the frequency factor, Do, were calculated for each system. Values of Q were found to be within 15 pet of that for self-diffusion of nickel in agreement with present theories of diffusion. ONE of the most interesting problems in diffusion concerns factors governing the order of diffusion coefficients of various solutes in a common solvent metal at low solute concentrations. An early suggestion by Rhines and Mehl' was that diffusion coefficients might each approach that of the self-diffusion coefficient of the solvent itself. Later Thomas and Birchenall' pointed out correlations between the order of the diffusion coefficients and the freezing point depressions of the solvent by the various solutes. Other correlations have been sought. To settle this question it seems likely that much more data will be needed and, in particular, data collected at low solute concentrations. This type can be obtained by special analytical techniques as well as by use of radioactive tracers. The following study was made of diffusion of manganese, aluminum, titanium, and tungsten in a common solvent, nickel, at relatively low solute concentrations: 1—Production of alloys of nickel with manganese, aluminum, titanium. and tungsten at concentrations of the order of 1 atomic pet. 2—Use of pressure-welded diffusion couples in cylindrical form. 3—Diffusion anneals in the temperature range of 1100" to 1300°C. 4—Lathe sectioning of the diffused couples. 5—Spectrophotometric analyses of lathe turnings for the solute being studied. 6—Calculation of the diffusion coefficient for each of the solutes as a function of temperature. 7—Interpretation of results with current theories of diffusion. Experimental Work Materials—Two types of nickel were used in this research. The grade designated as Vacuum melted Mond nickel was used for all diffusion systems except the Mn-Ni system for which the Vacuum melted electrolytic nickel was used. Analyses of the two grades are given in Table I. The manganese used in making alloys was 99.9 + pet pure, aluminum 99.99 pet pure, titanium 99.9 pet pure, and tungsten of C.P. grade powder. Alloys used in this investigation were prepared by melting in vacuo or under a low pressure of argon. After melting, all heats except those of nickel-manganese were poured into a cylindrical copper mold 3 in. long and 1 in. ID. In the case of nickel-manganese, the alloys were solidified in the melting crucible. For nickel-aluminum heats alumina crucibles were used and for all other heats, zirconia crucibles.

Jan 1, 1957

By A. W. McReynolds

One characteristic of plastic deformation which distinguishes it from elastic strain is the essential inhomo-geneity of plastic strains. Elastic strain varies continuously through a material, and average relative displacements of initially adjacent atoms are only small fractions of their initial spacing, (strains of the order of 0.01 or less). On the other hand, plastic flow corresponds to the appearance of discontinuities in strain of the lattice, such as dislocations or slip bands, where local strain, on an atomic scale, is several orders of magnitude higher. These discontinuities are visible on a microscopic scale as the familiar slip lines (Fig 1). In spite of this obvious microscopic inhomogeneity, however, macroscopic measurements almost invariably show a smooth curve of stress vs. strain (Fig 2b) even if measurements of linear strains be made to an accuracy of one part in 107. This macroscopic homogeneity of strain indicates that the discontinuities in strain on slip planes occur in increments too small or too slow to be recorded individually, and further that they occur sufficiently independent of one another so that the small increments add at random to a smooth stress-strain curve. The present paper describes observations of plastic strain in aluminum of commercial purity and in high purity Al-Cu alloys, where there exists a strong coupling between slip in various regions of the specimen such that once initiated it spreads rapidly through a large volume. The total effect is that of relatively large, rapid, and regularly spaced steps of strain followed by periods of only elastic strain. Fig 2a illustrates the type of "stair-step" stress-strain curve which results. The properties of this cooperative slip phenomenon will be described further in the section on results: in par- ticular it will be shown that each step corresponds to the propagation of a wave of plastic deformation through the specimen. Some interpretations of the mechanism by which it occurs will be made in the following section. Although the type of plastic wave phenomena to be described has not previously been reported, there are numerous cases of related effects in the plastic yielding of metals: YIELD POINT PHENOMENA The most familiar of such effects is the "yield point" observed in low carbon steels, brass, duralurninum, and the like. It consists in the sudden termination of the elastic portion of the stress-strain curve by a large plastic strain. Since the usual tensile machine is such that yielding of the specimen relieves the load, the resulting curve is as shown in Fig 3. As the strain continues, deformation occurs at a lower stress for some time, then follows a rising curve, but with no further sudden yielding. This effect has been observed in brass by Sachs and Shojil and later by many others. Edwards, Phillips and Jones2 made extensive studies of the effect in steel, and of the role of various alloying elements. Although there seems to be fairly clear evidence that the yield point is caused by a hardening of the material by precipitation of impurities, no satisfactory explanation for the sudden yielding has been given. Winlock and Leiter3 have shown that the strain. level of the upper yield point depends strongly on the rate of loading, the yield point increasing by almost a fac- tor of two as the strain rate goes from 0.002 in. per in. per min. to 4.4 in. per in. per min. This effect would seem to imply an incubation period before yielding is initiated at a certain stress. On the other hand, by going to very slow loading rates, Edwards, Phillips and Jones2 showed that the yield point does not become lower and eventually disappear as might be expected, but, on the contrary, begins to rise at loading rates below about 25 Ib per in. per min. becoming much higher than at rapid loading rates. STRAIN AGING If, instead of continuing straining of a specimen after occurrence of a yield point, the load is removed and the specimen aged, resumption of the test results in occurrence of another yield point as shown by the dotted curve of Fig 3. The new yield stress is generally higher than the previous maximum applied stress. This hardening of the material by straining and subsequent aging is undoubtedly related to quench age-hardening resulting from the aging of a specimen quenched from high temperature. Since neither effect is observed in pure metals, it is generally accepted that quench-aging in all cases is the result of hardening by precipitation of a supersaturated alloying element, and that strain-aging is probably a similar precipitation, accelerated by disruptions of the lattice by previous strain. Pfeil4 has shown that strain-aging does not occur in iron from which all of the carbon has been removed, but that only a very small carbon content, around 0.003 pct, is necessary to cause strain-aging. In accord with this observation is recent work by Dijkstra5 in this laboratory showing that the solubility limit of carbon in iron is extremely low, less than 0.001 pct at 400°C. Edwards, Phillips and Jones2 have shown that the strain-aging effect is also removed by the addition of small quantities of elements such as Mo, Mn, Ti, and the like, which readily form carbides. Their results demonstrate the

Jan 1, 1950

This brief resume of events, transpiring in Mexico, culled from the daily New York newspapers, since the last Bulletin went to press, does not indicate any degree of improvements in the situation. GENERAL ALVAREZ COURTMARTIALED AND SHOT General Francisco Alvarez of the anti-Government forces was captured in the battle in which General Aureliano Blanquet, Minister of War in the Huerta Cabinet, was killed, and was sentenced by a courtmartial and shot in spite of a specific order of the Supreme Court in Mexico City that the execution should not take place. General Alvarez was a member of the staff of Felix Diaz, and was a veteran of the old regular army of Mexico. MEXICO WILL NOT RECOGNIZE MONROE DOCTRINE Failure of the Allied Powers to invite Mexico to participate in the conference of neutrals at Paris aroused President Carranza to bitter resentment, which was enhanced by the incorporation of recognition of the Monroe Doctrine in the covenant of the League of Nations without consultation with Mexico. Statements were issued by the Mexican Foreign Office disavowing adherence to the Monroe Doctrine and announcing the withdrawal of the Mexican representative in France. Carranza had been awaiting an opportunity to get his agent away from Paris for the real reason that he had been unable to secure recognition from either the French or the British Government. Mexico announces, says the New York Times editorially, that "she has not recognized and will not recognize the Monroe Doctrine." "Nobody has asked her to recognize the Monroe Doctrine," continues the editorial. "The enforcement of the principles enunciated by President Monroe does not depend upon Mexico, upon anybody's recognition or non-recognition. The countries concerned in the Monroe Doctrine are the United States on the one hand, and countries not of this hemisphere on the other."

Jan 6, 1919

By S. A. Bradford

Internal-oxide precipitates in decarburized a iron alloys were studied by microscopic and X-ray methods. Diffusion of oxygen is primarily trans-granular, although large amounts of manganese or PhosPhorus cause preferred grain boundary dimsion at temperatures below 1450OF. Transgvanular internal oxidation follows the parabolic rate law with an apparent activation energy of 60 kcal per g-atom for decarburized rimmed steel and around 50 kcal per g-atom for higher alloy contents. The internal oxide is (Fe,Mn)0. Evidence was found for a miscibility gap in the FeO-MnO system. UNTIL very recently, the internal oxidation of metals was studied primarily as a scientific curiosity or, in a few cases, as a means of strengthening alloys by precipitation hardening. However, with the recent development of low-carbon enameling sheet steel, internal oxidation has become a problem of practical importance to the steel industry. For example, in 1961 it was reported1 that internal oxidation of steel can occur during decar-burization by open-coil annealing and will reduce the notch ductility of the sheet unless the process is carefully controlled. The present study was therefore undertaken to learn more about the rates and mechanism of oxygen diffusion and oxide formation in iron alloys. BACKGROUND The process of internal oxidation has been well-defined in the literature:',' oxygen dissolves in an alloy, diffuses inward from the surface of the metal, and reacts to form a precipitate with the alloying element that will provide the most stable oxide. he growth of the finely divided so-called subscale, i.e., the internal-oxidation zone, depends on the diffusion rates of both the oxygen and the reactive element.4 Investigators have generally found that increasing the temperature increases the size of the oxide particles, the rate of subscale growth, and the tendency to transgranular diffusion. With very few exceptions, the square of the thickness of the internal oxide layer is directly proportional to the reaction time. Given two conditions easily satisfied for iron systems— a) an oxygen solubility much less than the concentration of the alloying metal and b) an oxygen-diffusion rate to the oxide boundary much faster than that of the alloying element—then the general expression developed by Rhines and co-workers5 for the parabolic growth rate of the internal-oxide zone can be simplified to the following form: where Co and CM are, respectively, the solubility of oxygen and the concentration of the alloying element, DO is the diffusion coefficient of oxygen, O/M is the weight ratio of oxygen to metal in the precipitated oxide, and x is the thickness of the internal-oxide zone after an annealing time t. Both the oxygen solubility and diffusion coefficient can be approximately expressed as functions of temperature by Arrhenius-type equations: in which H and Q are, respectively, the heat of solution and the activation energy of diffusion. Consequently, the apparent activation energies calculated from Arrhenius plots are the sum of the heat of solution of oxygen in iron and the activation energy for diffusion of oxygen. The data, if not the interpretation, of Schenck et al.8 bear out the fact that oxygen diffuses in the atomic form. The general rate law for atomic diffusion is: the reaction rate being proportional to the square root of the pressure at low pressures. Benard and Moreau8 studied both the surface oxidation of Fe-Ni alloys and the gradual penetration of oxygen into the metal. They observed that oxide particles first form along grain boundaries and then grow to form continuous films that eventually envelop the grains. The parabolic rate law does not usually apply in these cases, especially at the higher temperatures. The oxide formed is wustite which gradually transforms into Fe3O4 and finally into Kennedy and coauthors8 examined Fe-Ni alloys with 26, 75, and 84 pct Ni oxidized at 800°C and

Jan 1, 1964

By F. V. Lenel, G. S. Ansell, J. A. Dromsky

The growth of aluminum oxide particles in a nickel matrix was studied eve?. the temperature vange of 2140° to 2470°F. The instability of the dispersed alumina was shown to be independent of the crystal structure of the alumina. The activation energy for the growth of the dispersed alumina was found to be 84.7 1 2.0 kcal. The particle radius increased as a function of time. These results indicate that the growth is not diffusion controlled. It is believed that the rate controlling mechanism is the dissolution of the aluminum and oxygen atoms into the nickel lattice. THE strength properties of alloys which consist of a finely dispersed second phase in a metallic matrix depend upon the spacing between the second phase particles. It is therefore desirable to achieve very fine dispersions in these alloys. Furthermore, to retain the properties these very fine dispersions must be stable during fabrication and service of the alloys. The best known of the dispersion strengthened materials, the SAP type alloys, which consist of a dispersion of aluminurn oxide in aluminum, have exceptionally good stability up to the melting point of aluminum. There is evidence, however, that other dispersion strengthened alloys, even those consisting of refractory oxides in a metal matrix, may be less stable. This investigation is concerned with the stability of Ni-Al2O3 alloys in the temperature range in which these alloys are usually fabricated. The mechanical properties of Ni-Al2O3 alloys at elevated temperatures have been previously investigated by Crelnens and rant,' and Gregory and Goetzel.2 The behavior of these alloys in stress rupture tests appears to indicate that at temperatures below 1800°F they are highly stable. There is some doubt, however, as to their stability at the higher temperatures used during the conventional fabrication. Cremens and Grant, in preparing their test alloys, cousolidated, by powder metallurgical techniques, nickel powders as fine as 0.13 µ diam and alumina powders as fine as 0.018 µ. Metallo- graphic examination of the alloys following fabrication revealed that none had interparticle spacings of less than 2 µ. Considering the size of the original component powder particles, it is likely that the dispersions coarsened during fabrication. Gregory and Goetzel, in their studies of extruded alloys of 80 pct Ni—-20 pct Cr matrixes with nonmetallic dispersion, observed a definite coarsening of the alumina dispersions in alloys sintered at 2280°F as cantrasted to those sintered at 2000oF. Similar observations on the spheroidization and growth of thoria particles finely dispersed in a nickel matrix were made by D. K. Worn and S. F. Marton.3 As a result of such coarsening, much of the effort expended in the preparation of very fine powder mixtures would be lost. The mechanical properties of the alloys which had experienced coarsening would be expected to be poorer than if the original dispersions had been retained. EXPERIMENTAL PROCEDURE Ni-Al2O3 alloys were produced from powder prepared by a coprecipitation technique. Aluminum hydroxide and nickel hydroxide were coprecipitated from chloride solutions of the metals. The mixed hydroxides were calcined to form metal oxides and the nickel oxide in the mixture was selectively reduced to nickel by treating it in hydrogen. Specimens were compacted from the resultant powder which consisted of a fine, uniform mixture of aluminum oxide and nickel particles. The compacts were sintered by resistance hot pressing4, a densification technique which requires exposure times of the order of only a second or less at elevated temperatures. A conventional sintering process was not used, since the temperature required for densification would have to be in the region in which the stability of the dispersion was to be studied. A series of hot pressed specimens were treated in hydrogen at temperatures from 2140o to 2470°F (1171o to 1355oC, for times up to 120 hr. Changes in the microstructures were studied by electron microscopy using the two-stage preshadowed carbon replica method.5 In performing a lineal analysis on a series of micrographs from each specimen it was found more convenient to determine the mean free path between alumina particles rather than particle radii as the parameter of growth. Although these quantities are directly proportional for only spherical particles, the alumina particles in these alloys

Jan 1, 1962

This brief resume of the events transpiring in Mexico, culled from the daily New York newspapers since the last Bulletin went to press, does not show any degree of improvement in the situation. MEXICO SEEKS TO AVOID BLAME FOR BANDIT RAIDS All foreign passengers leaving Nogales for Mexico on the Southern Pacific or Mexico Railroad. whose business would take them through territory occupied by the Yaqui Indians or Mexican bandits were requested by Mexican Consul Emilio Tamez to sign a statement that they relieve the Mexican government of responsi-bility for anything which might happen to them while in that part of Mexico. The Mexican consul stated, says the N. Y. Tribune, that this was by order of Mexican Ambassador Ignacio Bon ill as, at Washington. When the State Department was advised of this activity Secretary Phillips, in a message to the consulate at Tampico, according to the N. Y. Tribune, asserted that "compliance with the waiver requirement will not interfere with the relation existing between the United States and its citizens and that Americans so complying will in no way lose the protection of this government."

Jan 11, 1919

By Philip J. Shenon

IN 1947 the mining industry strove desperately to regain operating normalcy. During the first part of the year the industry in this country was plagued with labor shortages, strikes, and portal-to-portal lawsuits. Then followed the uncertainty of Government policy with respect to subsidies and tariffs; and the long and bitter controversy as to whether we are a nation of mineral "haves" or "have-nots." As the year progressed the labor supply impoved somewhat and the Taft-Hartley law brought partial relief to strike-troubled industry. The uncertainty with respect to tariffs was partly answered by President Truman on April 29 when he announced the suspension of the 4¢ import duty on copper until March 31, 1949, and later, near the close of the year, by the announcement of the tariff agreement signed by the United Nations at Geneva. By this agreement tariff rates are to be adjusted downward, or "bound" at their present levels, for three years, on commodities amounting to some 60 per cent of United States trade. Effective Jan. 1, 1948 the rate of duty will be substantially reduced on ores, concentrates, or metals of zinc, aluminum, copper, manganese, tungsten, iron, steel, barytes, nickel, cadmium, and antimony.

Jan 1, 1948

By Jo. E. Sheridan

The Dawson coal-mines are owned aid operated by the Stag Canon Fuel Co., of which Dr. James Douglas is President and E. L. Carpenter general manager. The property is situated in Colfax county, N. M., and the openings now in operation are in townships 28 and 29 N R. 20 E., and township 28 N E. 21 E., shown in Fig. I. The mines are part of the southern end of the Raton coal-field, which extends north into Colorado and embraces many coal-camps of the Trinidad section. II. Geology. Geologically, the coal-measures, commonly known as the Laramie series of the Cretaceous system, have x thickness of about 800 ft. in the vicinity of Damson. The coal makes an excellent coke, and, according to some authorities, its coking properties are due to the action of intruded sheets and sills of igneous rock, the sheets occasionally thickening into masses resembling laccoliths, at such places making nearer approach to the coal and sometimes producing small areas of natural coke. There are but few dikes throughout the entire southern portion of the field and little or no faulting along the dikes. In some parts of this great coal-field the intrusive sheets are far removed in the green shales below the coal-measures, and are so much altered as to be difficult of identification. There is but little disturbance of the strata throughout the Raton coal-field in as far as it extends into New Mexico. There are two workable seams in the coal-measures, and two or three smaller coal-seams, ranging from 1 to 2.5 ft. in thick-

Jan 1, 1910

By D. D. Porter, H. G. Carlevato

Blasting to prepare orebodies for in situ leaching usually involves extraordinary conditions which sometimes require special and innovative techniques. To date several unusually large blasts have been made for leaching with results that are very encouraging. Among the factors considered when designing these large blasts are orebody shape and depth, rock properties, vibration and damage potential, loading logistics, and safety. All of these factors, and others, are discussed with an effort made to put each of them into its proper perspective.

Jan 1, 1974

By George Krauss, M. Cohen

The reverse martensitic transfomzation (i.e., the conversion of martensite to austenite on heating) was investigated in Fe-Ni alloys containing 30.5 to 33.5 wt pct Ni. The reversed austenite was found to be sufficiently distorted to exhibit marked differences in mechanical properties and to undergo recovery and re crystallization on further heating. In particular, the yield strength of the reversed austenite was as much as 2.5 times higher than that of the virgin austenite: with five cycles of the direct and reverse martensitic transformation, the yield strength was 2.6 times higher. There was an accompanying decrease in strain-hardening capacity and in stable ductility or uniform elongation. The recrystallization was observed to follow sigmoidal kinetics, but was characterized by an abnormal1y large temperature dependence which was evidently due to carbon segregation at the migrating grain boundaries. Upon recrystallization, the strength Properties reverted to those of the virgin austenite, but the ductility did not fully recover until the annealing temperature was further raised to dissipate the carbon segregation at the grain boundaries. The transformation of reversed austenite to produce second-generation martensite resulted in an unusually imperfect structure, thereby leaditg to additional strengthening. Horlleuer, the martensitic phase was much less responsive in this respect than was the austenite. MOST martensitic transformations are capable of undergoing a reverse transformation back to the austenitic phase on heating.&apos; This reaction, like the direct transformation to martensite on cooling, is usually athermal. In analogy with the Ms andMf temperatures for the martensitic transformation (where M, > Mf), the reverse transformation is characterized by the As andAf temperatures (where As<Af). It is well-known that the finish (Af) of the martensite-to-austenite reaction on heating may occur at a temperature where austenite is not stable relative to other phases in the equilibrium diagram.&apos; Reverse martensitic transformations have been found to influence the properties of the parent austenitic phase in a number of ferrous alloys. The austenite thus produced after one or more reversals is significantly altered in strength, microstruc-ture, diffusivity, and annealing characteristics compared to well-annealed, virgin austenite. The first detailed observations of such phenomena were made by Wasserman3 on an Fe-30 wt pct alloy. He found that the reversed austenite (i.e., austenite formed by the reverse martensitic transformation) was much stronger than the original austenite, and the second-generation martensite (i.e., martensite produced from the reversed austenite) was somewhat stronger than the first-generation martensite. On heating the reversed austenite, recrystallization occurred in a manner similar to that of a cold-worked metal; the Laue spots sharpened and the strength decreased.4 In recent years, Russian workers have shown considerable interest in these reverse martensitic transformations. Most of such investigations5-10 have been concerned with the stabilization of reversed austenite relative to subsequent martensitic transformation, and because of its unusual nature, this phenomenon will be discussed in detail elsewhere." On the other hand, the annealing behavior of reversed austenite and the attendant variation in properties have received little attention beyond the experiments of Wasserman.3,4 Gridnev eta1.,8 in one of the few such studies. followed the hardness change of reversed austenite as a function of time at three annealing temperatures. The marked strengthening of austenite achieved by the reverse martensitic transformation has been referred to as "transformation strengthening" by Wasserman3,4 and as "phase hardening" by Malyshev et a1.7,9,10 to differentiate it from hardening produced by cold working. Both groups of investigators noted that further strengthening of the austenite could be attained by repeated or cyclic transformations, but the first cycle resulted in the most pronounced effect. Evidence of the altered microstructure of reversed austenite has been reported by Maximova and Nikonorova6 and by Edmonson and KO.12 The former found that reversed austenite was much more sensitive to etching than the original austenite, and the latter authors observed a (&apos;ghost" structure resembling martensite in certain areas of the reversed austenite. Enhancement of the self-diffusion rate in reversed

Jan 1, 1962