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By K. R. Garr, D. Kramer, A. G. Pard

EXPOSURE of steels to a fast-neutron flux results in helium generation by (n,a) reactions. The elements Fe, Ni, Cr, and N are major participants in the (n,a) reaction and helium concentrations of up to 5 x 10"5 atom fraction could accrue in fuel clads after a year of service in proposed fast reactors.' Such concentrations of helium can severely reduce the ductility of alloys at temperatures of reactor service. The phenomenon of helium embrittlement has been studied in austenitic alloys which were irradiated with particles as a rapid means of producing significant helium concentrations.2-5 The pres-ent work is a continuation of those studies and is concerned with helium effects in a ferritic stainless steel. I) EXPERIMENT Small sheet tensile samples with a gage length of 0.50 in. and a cross-section of 0.009 by 0.040 in. in the gage length were punched from cold-rolled type 405 stainless steel. The composition of the steel used in this work is given in Table I. Prior to helium injection, the samples were annealed 24 hr at 760°C which caused complete recrys-tallization with a resulting grain size of 40 u. This treatment rendered the alloy completely ferritic and carbide particles, 0.5 to 2 uin size, were present at a density of 1 x 1011 cm-3, Fig. 1. These carbide particles were probably a mixture of the M7C3 and M4C types.6 Helium was injected into the samples by irradiation with a particles from a cyclotron, which produced uniform concentrations through the center two-thirds of the sample thickness. Details of this procedure were previously described.' The average helium concentration, as measured on a gas-source mass spec- 11) RESULTS A) Tensile Tests. The results of the tensile tests are given in Table I1 where the values shown are averages of two samples. There was no significant effect of helium on either the yield strength or tensile strength at 550" or 650°C but an increase in both is apparent at 750°C. Samples with helium showed a 20 pct loss in total elongation at 650°C which increased to a 55 pct loss at 750°C. The uniform elongation is not affected by helium at 550" or 650°C but shows an increase at 750°C.

Jan 1, 1970

By W. O. Crosby

INTRODUCTION. THE crystalline belt of the Atlantic Seaboard, south of New York, attains its maximum breadth of 220 miles on the northern border of North Carolina; and in this State it is most widely characterized by the occurrence of gold in workable deposits. Half a dozen auriferous belts have been recognized by Nitze and Hanna.1 These are, in the main, coincident in position and trend with the NE.-SW. zones of metamorphic slates and schists, which, more than any other feature, give character to the geological map of North Carolina. The central gold-belts, accompanying the main zone of slates and associated igneous rocks, are much the more important and persistent, and may be regarded as continuous northward across Virginia and southward into South Carolina. Tile eastern belt, on the other band, is the shortest and, economically, one of the least important. Its extreme length does not exceed 25 miles, the narrow band of slaty rocks to which it belongs passing, both NE. and SW., beneath the coastal-plain formations. But, although limited in area and production, this belt is, perhaps, comparable with the central belts or any part of the sea-board crystallines in the variety of conditions under which the gold occurs. It lies chiefly in the NE. part of Franklin county and the NW. part of Nash county, on the watershed of Fishing creek and other tributaries of Tar river. The elevation is between 400 and 500 ft. ; and the Tertiary peneplain has here an exceptionally perfect development, the reliefs separating the slightly incised stream-courses consisting of broad, flat-topped peneplain remnants, bounded by gentle lateral slopes.

Mar 1, 1908

By P. R. Gage, R. W. Bartlett

SILICIDE coatings on refractory metals are often applied by transporting a silicon halide vapor to a hot metal surface where dissociation or hydrogen reduction occurs. The subsequent chemical reaction to produce the coating requires diffusion of silicon or the refractory metal through the in situ silicide layer. This solid-state diffusion process step is often slower than the vapor-transport step and, therefore, rate controlling. This situation is analogous to the parabolic oxidation of metals in which the oxidation rate is controlled by diffusion through the oxide layer. The purposes of this study were to 1) measure the rate of formation of MoSiz and MoSi2 coatings under conditions such that the silicide diffusion process is rate controlling and lower silicide compounds are not formed and 2) determine by a marker experiment whether silicon or the respective refractory metals are the principal diffusing species in the disilicides.

Jan 1, 1965

By I. R. Kramer

In his technical note entitled "Specimen Temperature During Electropolishing of Aluminum Crystals" Dr. Nakada 1 reported that the temperature of his aluminum specimen increased 65°C when it was polished electrolytically; he therefore concluded that the temperature of the specimens used in our work (Nakada's Refs. 4 and 5) similarly increased by this amount. From this he further concluded that the change in plastic-flow characteristics associated with the removal of the surface by electropolishing during deformation were due solely to a temperature effect. We believe that these conclusions are not justified. It is, of course, realized that the amount of the temperature increase is associated with the total heat transfer of the entire system, including the efficiency of the stirring action, heat flow through the grip on the specimen, and so forth. Of great importance is the type of electrolyte used for polishing. For example, in Dr. Nakada's experiment a methanol-perchloric acid solution was used. This solution has a relatively low conductivity and for the current densities of 0.3 amp per sq cm the electrical input appears to be 30 to 40 w. In our research a methanol-nitric acid solution was employed and for the size of specimen employed by Dr. Nakada the power never exceeded 7 w. There are major differences in his test apparatus which also appear to affect the temperature rise. In our case a steel specimen holder was used in order to provide a good heat sink and conduction path. The cathode was a coiled aluminum tube through which a coolant was passed to provide additional cooling capacity near the specimen. The stirrer was placed in a position to obtain maximum cooling efficiency. On the other hand Dr. Nakada used a teflon grip to support the specimen at one end only and a flat copper cathode, thus providing a much less efficient heat sink as compared with the metal grips used in our studies. The relationship between current density and the temperature increase for two sizes of aluminum crystals tested in our tensile apparatus is shown in Fig. 1. The temperature measurements were determined from a thermocouple spot-welded to the surface of the specimen. The thermocouple was protected from the acid by means of a thin film of stop-off lacquer which covered just the outer surface of the thermocouple junction. Whereas Dr. Nakada reported a time delay of 8 min to obtain thermal equilibrium, our temperature change occurred in less than 15 sec. This emphasizes the importance of the heat transfer in the entire system. However, readings were taken over a period in excess of 5 min to assure thermal equilibrium. The data given in Fig. 1 were also confirmed by determining the thermal expansion of the specimen in a sensitive creep apparatus. As may be seen, for the smaller specimen the increase in temperature is 8°C for a current density of 1.5 amp per sq in. The majority of our data on the effects of surface removal on the plastic behavior of aluminum were obtained at current-density values at or below this value. Above 1.5 amp per sq in. the temperature rise is uncertain; for under certain conditions, especially in the vicinity of 2 amp per sq in., the anode can become polarized and the current flow is erratic. This condition is easily recognized because wide fluctuations in the creep and stress-strain data make it virtually impossible to obtain reliable results, a condition which was always avoided in our work. The temperature increase for the larger specimen is less than that of the smaller specimens below a current density of 1.5 amp per sq in. At a current density of 2 amp per sq in. the temperature increased 13°C. The above temperature data are in accord with observations made during creep experiments. Using a transducer capable of detecting strain in the order of 10 -6, temperature changes in excess of 8°C were not detected when the current density was increased to as high a value as 1.5 amp per sq in. Finally we wish to point out that our experimental data cannot be explained solely in terms of a heat effect. For example in Fig. 1 of Ref. 2, the change in slope of Stage II as a function of the rate of re-

Jan 1, 1965

By G. A. Vissac, R. G. Minet, N. E. Sylvander

R. G. Minet—The authors' description of the remarkable progress made in the last few years in applying the fluidized solids technique to the problem of lignite drying and carbonization clearly demonstrates that engineering techniques available today may make many processes practical and profitable which a few years ago were considered otherwise. As pointed out in the article, the future of the carbonization step hinges on the value and utilization of low temperature tar. On paper, at any rate, this tar looks like a valuable raw material for the chemical industry to use. Some 50 to 60 pct may be converted to pitch for electrodes, roofing, road tars, and other valuable products; the 25 to 30 pct tar acids could conceivably form a basis for a new low cost resin or plastic of the phenolformalde-hyde type. Yet these materials are so new and dissimilar from available sources that much work must be undertaken by the chemical industry before they will be accepted. Now that the work of Dr. Perry and his colleagues has made a large supply of low temperature tar a real possibility, I would expect the chemical industry to accelerate its work in this field. On the basis of certain data available in the literature it appears possible to produce a more aromatic tar, although in smaller yield, by operating at temperatures in the range of 1300" to 1500°F. Operating a fluidized bed process for lignite at these conditions should be technically possible, at least, and could produce a tar having more familiar characteristics. I wonder if Dr. Parry would care to comment on such a possibility. Incidentally, in our own work on carbonizing coking coals in fluidized beds, using Ohio, Pennsylvania, and West Virginia high volatile bituminous coals, we have obtained yields which agree with the correlation given for tar yields vs moisture and ash-free volatile Btu. Our data are slightly under the line, but certainly in the range of the correlation. We have also obtained evidence in support of the authors' statement as to the effect of air on the process. In our pilot plant all the heat required for carbonizing is released by internal combustion of char in the fluidized bed in normal operation. We are also equipped to obtain all carbonization heat by external electric heaters on the shell of the carbonizer while introducing only an inert gas to the process. We note no difference in tar yield or characteristics between the two operations. In the case of the gas, however, it appears that some hydrogen is consumed by the air combustion. We would be interested in hearing in a little more detail about the hot dust and char handling problems at Sandow. Have the authors found char subject to spontaneous combustion? Have they ever tried a coking coal in their pilot plant? V. F. Parry (author's reply)—Production of a more aromatic tar by operation of the carbonizer at 1300" to 1500°F does not appear to be economical. 1) The capacity of a reactor operating at 1500°F would be 30 to 50 pct less than the capacity at 932 °F and the cost of processing would increase materially. 2) The cracking of tar vapors in a reactor requires appreciable time to complete the reactions and it is doubtful that considering the very short time of residence of tar vapors within the reactor (4 to 10 sec after evolution) the basic character of the tar would be changed significantly. This is indicated from the data reported in Table XIV. 3) General studies have shown that it is advisable to operate at the minimum temperature to produce the maximum tar and minimum gas. 4) Operating problems and the maintenance of vessels and reactors, and the hazards of handling hot char, increase with the temperature of carbonization. It is technically possible to operate at temperatures as high as 1500°F, but in my opinion it is not economical or desirable. We believe that the primary tar must be won in the simplest way and then processed alone to change its character for production of desired products. It is interesting to have confirmation of our observations on the reaction of air with the products of carbonization. The major reaction is with the char, fol-

Jan 1, 1957

By R. H. Wightman, G. H. ADAM

In order to secure good results in the prevention of accidents, it is generally recognized that the desire for such accomplishment, as well as the aggressive and constructive action to achieve it, must emanate from the Top Management and permeate successively down through the "Chart of Authority" to the workmen. Several years ago, with the above as a basis and with full support of the Top Management, the Mining Department started a program of selling the foremen and bosses the idea that safety could be achieved and that it was desired and required. Using psychology, persistence and numerous other methods, the foremen and bosses were finally impressed with the idea that "It can be done" and "It will be done." With this in mind, new ideas were brought forth by the foremen and bosses regarding the caving operation and the specific jobs in the operation. These new ideas were taken up in round-table discussions and resulted in certain changes in the undercutting method and the actual drawing of the blocks. These changes resulted in increasing fragmentation of the blocks which prevented the usual hang-up areas in the blocks. With the rock smaller in size and within reasonable reach from the tapping drifts, accidents were prevented in the tapping section. At the same time, an enforced campaign of housekeeping throughout the mine was undertaken with very beneficial results. The foremen and bosses then, in turn, educated and trained the workers themselves to become safely conscious. In so doing, a constant re- minder was given on all jobs assigned that the job was to be done safely as well as efficiently. No man is assigned a job who is not qualified for the type of work required. Efficiency and safety go hand in hand.

Jan 1, 1949

By Robert B. Fulton

Commercially, celestite (SrSO4) is the predominant strontium mineral. Among other strontium-bearing minerals, only strontianite (SrCO3) occurs commonly; however, it is rarely an item of commerce. Production of celestite is principally in Mexico, Spain, and Turkey. An attempt to produce celestite in Canada was unsuccessful. The United States, which is wholly dependent on imports, chiefly from Mexico (99%), is the largest consumer of strontium. Lesser quantities are consumed in Japan and Europe. The Federal Republic of Germany is the principal source of strontium compounds imported to the US. Uses The principal uses of strontium are for the manufacture of strontium carbonate and nitrate. Carbonate is used in glass for TV tube face plates and in ceramic ferrites for magnets. Nitrate is used in pyrotechnics, mainly in safety flares, to which it imparts a characteristic brilliant red color. Minor amounts of strontium compounds are used in electrolytic zinc manufacturing where the carbonate is used to remove unwanted lead. Small quantities are consumed in greases, ceramics, soaps, alloys, and pharmaceuticals. Specifications Typical celestite specifications for the carbonate and nitrate markets are shown in Table 1. Specifications of manufactured carbonate, sold in two grades, one to the glass industry and the other for ceramic ferrites, are shown in Table 2. Both grades of carbonate are shipped in palletized 50-lb bags. Glass grade material is shipped in bulk by rail. [ ] Manufacturing Processes The following description is adapted from Anon. (1980) . The manufacturing process for strontium carbonate and strontium nitrate chemicals is conceptually simple. Strontium nitrate is made from strontium carbonate in two additional steps. The production process begins with celestite, the natural form of strontium sulfate. In the first step the ore is crushed, ground, and mixed with coke. This mixture is then fed into a kiln where the ore is reduced at high temperatures to strontium sulfide; the coke is added to the ore as a source of energy and carbon. The carbon combines with the oxygen [ ]

Jan 1, 1983

By George H. Hanna

THE importance of the Donets coal field (the Donbas) to the national economy of the Soviet Union is well known. Great as was the significance of this tremendous deposit of coal in prewar days it is destined to become an even greater factor in the economic life of the country now that the tremendous havoc wrought by the Germans is being remedied. Since the war began, new coal fields have been extended; for example output of the Moscow and Karaganda (Kazakhstan) fields has become considerably larger while new mines are producing coal in several parts of Uzbekistan and Kirghizia. The huge West Siberian coal field, the Kuznetsk Basin, is producing more coal than ever before to supply the industries of that region and of the Urals. But so great has been the development of industry to meet war needs, especially in those districts of the Soviet Union that lie to the East of the Urals, that the coal obtained, eked out by such locally-won fuels as peat and wood, is still barely sufficient to meet industrial requirements. The main burden of the coal supply for the restored industries of the West, therefore, will fall on the Donbas.

Jan 1, 1945

By R. D. Springer, R. L. Wilcox, P. A. PALMARTAN, R. K. Waring, E. A. Anderson

A knowledge of the mutual liquid solubility of zinc and lead is of importance in various phases of zinc metallurgy. The determination of this solubility has been the subject of numerous investigations, but unfortunately the results vary widely, particularly at higher temperatures, and it has been impossible to decide what data are most reliable. It was decided to investigate the matter and in view of the disagreement in the published results, it was felt necessary to take rather unusual precautions to insure the reliability of the data. For this reason determinations were made by four different methods, and the procedures of several of the previous investigators were duplicated. The previously used methods can be divided into two classes: methods involving freezing the entire melt and taking samples of the lead-rich and zine-rich phases in the solid state,l,2 and methods in which the samples are taken while the bath is liquid and at the desired temperature.3,4 Data obtained by methods involving freezing the entire melt show much lower solubility of lead in zinc than methods in which the liquid is sampled at temperature. The latter method was used by Spring and Romanoff5 and by Hass and Jellinek.6 The results of these two investigations are in agreement at temperatures near the melting point but at higher temperatures Hass and Jellinek find a higher mutual solubility. The low-temperature section of the zinc-lead equilibrium diagram is given by Peirce and Anderson.7 The diagram is based on the data of Hodge and Heyer,8 Arnemann,9 and Peirce.10

Jan 1, 1934

The American Society of Mechanical Engineers extends an invitation to members of the Institute to participate in an exceedingly interesting excursion on Saturday, November 11. Permission has been secured for a visit to the plant of the Electric Boat Co. at New London, Conn. There will be run a special-test on a high-power 8-cylinder, 4-cycle Diesel engine. A large number of submarine and other engines in various stages of construction will be seen, also the boring of torpedo tubes, cylinders and other equipment for submarines. The drafting rooms and foundry mill also be open for inspection. The party will have an opportunity to see at close range the submerging of several submarines, and an attack on a vessel on the surface, an exhibit which is being arranged by courtesy of Rear Admiral A. W. Grant, who is in command of the submarine forces of the United States. The Boston members will leave South Station on train No. 7 at 8.30 A. M. Those from Providence will board this train at 9.36 A. M. The Worcester members will leave on train No. 745 at 8.36 A. M. The New York contingent will leave the Grand Central Terminal at 8.31 A. M. on train No. 8. This train will leave New Haven at 10.30 A. M. Upon arrival at New London, each group will go directly to the Mohican Hotel, where a "get-acquainted" luncheon will be served

Jan 10, 1916

(The paper by L. H. De Wald-Tech. Pub. No. 429 was presented at the Boston meeting, September, 1931.) W. A. SCHEUCH, Chicago, Ill.-Since starting up our Hawthorne copper wire plant we have found that wire bars from certain suppliers perform quite differently from those of other suppliers. In attempting to evaluate these bars, we made cross-sections, and in making these cross-sections we found considerable variation in the crystal structure. Indications were that there was some preference in the type of crystal structure. In attempting to find the reason for that we discussed it with the various producers and-also reviewed the literature. Mr. DeWald was assigned to determine the various factors that enter into copper wire bar crystal structure, on the basis that the product was a horizontally cast wire bar of practically identical composition and of recognized good composition for the present quality product sold in the market. Mr. DeWald has asked me to say that he should have made reference to Mr. Dalzell's paper on a theory concerning gases in refined copper. D. K. CRAMPTON, Marion, Conn. (written discussion).-Mr. DeWald has set forth an interesting and thorough exposition of the factors controlling macrostructure of this material. It is particularly interesting to us as it somewhat parallels work we have done on macrostructure of round copper billets for piercing into tubes. Our findings as to the effect of the several variables on macrostructure check Mr. DeWald's. The general principles underlying the two are precisely the same. The fact that we worked with copper deoxidized with phosphorous instead of tough-pitch copper, and round billets cast on end instead of wire bars, does not influence the results. We have found that round billets cast so as to produce large radial grains have greater soundness and density than those with a fine macrostructure. Further, and more important, we have found that the billets with large radial grains show markedly different performance on piercing from those having a fine equiaxed structure. With a given temperature of billet and adjustment of piercing machine, the coarse-grained material requires appreciably lower power for piercing and goes through the operation inn appreciably less time. These two differences are of sufficient commercial importance to warrant exercise of great care in maintaining the coarse structure. It seems probable that much the same phenomenon should hold in the hot rolling of tough-pitch wire bars. We would expect that, other things being equal, the coarse-grained wire bars would roll more readily and require less power than fine-grained ones. Moreover, we believe the differences in initial structure of the wire bars should be largely eliminated in the hot rolling process and during the subsequent drawing and annealing, of wire would be entirely eradicated.

Jan 1, 1932

By F. C. Blickensderfer

DURING 1914 and 1915 extensive experiments were conducted at the concentrator of The Detroit Copper Mining Co. of Arizona, at Morenci, Ariz., in order to test the relative grinding efficiencies of the Marathon, the Chilean and the Hardinge Mills. The Marathon mill used in the experiments was the first one ever built by the manufacturers; and since this was the first time that it was given a thorough tryout, with such remarkable results, the data have been, assembled in the following paper and submitted in the interests of the milling profession.

Jan 8, 1916

Receipts General Funds: Initiation fees ' 6,008.50 Arrears of dues 1,772.69 Current dues 46,576.56 Advance dues 1,820.97 Sale of binding 10,554.43 Sale of advertising 6,003.42 Sale of Transactions 3,237.07 Sale of special editions ' 1,722.50 Sale of Bulletins and. pamphlets ' 2,263.95 Miscellaneous Receipts; Interest on investments and deposits 450.06 Sale of pins and fobs 312.80 For the collection of checks 161.84 From Finance Committee, Feb., 1916, Meeting 101.02. Subscriptions to the land fund 86.14 Arizona Meeting refund from N. Y. Central Railroad.. 52.48 Local Section refund from N. Y. Central Railroad.... 31.85 Miscellaneous 425.68 Total Receipts General Funds 81,611.96 Cash balance Dec. 31, 1913 1,063.39 $82,675.35

Jan 2, 1917

By Henry A. Stiff

The classification and correlation of water analysis data presents many problems which can be solved by graphic methocis. The pattern system, a new type of graphic procedure described in this communication, is believed to have several advantages over older methods. Examples of the application, of the pattern system to the solution of problems encountered in petroleum production are given. INTRODUCTION Several graphic methods for presenting analytical water data have been developed and are now in use.1,2,3,4 It is believed, however, that a recently developed type of graph called the "pattern" offers several advantages over other methods. This system presents a better picture of the total salt concentration than is usual in such graphs. The effect of dilution or concentration has been reduced to a minimum, and at the same time distinction between various types of water has been improved. The system is extremely versatile, yet so simple it can be plotted on ordinary graph paper and adapted to almost any type of filing system. DISCUSSION The essential feature of the pattern system is the graph shown in Fig. 1. Horizontal lines extending right and left from a vertical line at zero form the graph. Positive ions are plotted to the left while negative ions are plotted to the right. The figure immediately beneath each ion gives the scale. Most oil field waters can be plotted on a scale where 100 milli-equivalents of sodium and chloride and 10 milliequivalents of each of the other ions are represented by one scale unit. For highly concentrated brines, 1,000 milliequivalents of sodium and chloride and 100 milliequivalents of each of the

Jan 1, 1951

By Henry A. Stiff

The classification and correlation of water analysis data presents many problems which can be solved by graphic methocis. The pattern system, a new type of graphic procedure described in this communication, is believed to have several advantages over older methods. Examples of the application, of the pattern system to the solution of problems encountered in petroleum production are given. INTRODUCTION Several graphic methods for presenting analytical water data have been developed and are now in use.1,2,3,4 It is believed, however, that a recently developed type of graph called the "pattern" offers several advantages over other methods. This system presents a better picture of the total salt concentration than is usual in such graphs. The effect of dilution or concentration has been reduced to a minimum, and at the same time distinction between various types of water has been improved. The system is extremely versatile, yet so simple it can be plotted on ordinary graph paper and adapted to almost any type of filing system. DISCUSSION The essential feature of the pattern system is the graph shown in Fig. 1. Horizontal lines extending right and left from a vertical line at zero form the graph. Positive ions are plotted to the left while negative ions are plotted to the right. The figure immediately beneath each ion gives the scale. Most oil field waters can be plotted on a scale where 100 milli-equivalents of sodium and chloride and 10 milliequivalents of each of the other ions are represented by one scale unit. For highly concentrated brines, 1,000 milliequivalents of sodium and chloride and 100 milliequivalents of each of the

Jan 1, 1951

M. G. CORSON.'-I am not going to discuss any of the papers presented but merely the question of season cracking of brass in general. Alpha brass has been known for nearly 500 yr. and from the very beginning a number of articles were made from sheets of this alloy by the process of spinning. Metal turning lathes were not yet known but wood turning lathes already existed and the wood turners used to make the mandrils and do the brass spinning themselves. Cases of season cracking were known even then. In 1915 I was connected with a small company doing a certain amount of brass spinning. Before the war its products never gave cause for complaint but their war-time products were cracking too frequently. The reason was, that due to the exigencies of war an excessive speed-up was attempted and the material simply could not take it. Today corrosion cracking of brass is most important in the case of cartridges for small arms ammunition and shell cases for large guns. The cracking takes place in storage and too frequently it is explained by the hypothetical presence of vapors of ammonia. However, I had the experience of purchasing some 20,000 rounds for the old Vetterli rifle from the Swiss government in 1905. The rifle and the cartridges were obsolete for many years and those which I bought were stored for at least 10 yr. None of them was found to be cracked or to crack in use. And the reason again was in the amount of work used in manufacturing the cartridges between anneals. The machinery today is more powerful and the amount of

Jan 1, 1945

By A. Mitchell

An approximate phase diagram has been developed for the CaF2-CaC2 system, indicating a eutectic point at 1240°C, Ncac2 = 0.13, and no detectable solid solution in either phase. The liquidus line is shown to correspond to a simple c22- ion in solution. A thermo-chemical study of&apos; the reaction between carbon-saturated Ni-Ca alloys and CaC2-CaF2 liquids indicates that lhe Raoullian activity coefficient of CaC2 in dilute solution in Cap2 al 1500°C lies between 8 and 10. Some effects of the stabilily of Cap2-CaC2 solutions at high temperatures on electroslag remelting praclice are outlined. THE alkaline earth acetylides. MIIC2, have a reasonably high thermochemical stability at high temperature in the solid state,&apos; with the exception of magnesium, which forms an unstable acetylide at low temperatures (-500°C) and a carbide, Mg2C3, in the range 700&apos; to 1000°C. The acetylides of calcium and barium have been shown to have limited solubility in their respective chlorides,&apos; and further these solutions contain the acetylide as a C: ion.&apos; The equivalent magnesium solutions have not been studied. Although calcium "carbide" is used as a desulfuriz-ing reagent in steelmaking. and is possibly present as an acetylide-oxide phase in very basic electric arc practice slags, the acetylide ion appears to be substantially unstable in a silicate slag.* As a conse- *This instability arises from equilibria in the reaction: CaC2 + CO = (Ca0) + 3C where the low intrinsic solubility of CaC2 in silicate lattice, and the low activity of CaO in a silicate solution where CaO/Si02 < 1, combine to give a very small equilibrium concentration of CaC2 in solution in such silicate slags at temperatures in the region of I 500°c, even under carbon-saturated conditions. Under highly basic conditions, a liquid CaO-CaC2 phase may separate from the silicate system quence of this, the possibility that reactions involving CaC2 in silicate solutions are of importance to general steelmaking practice is remote. However, in operations involving a slag primarily based on a halide, or alkaline earth oxide, we must take into account the possibility that CaC2 will appear in quantities sufficient to significantly affect both the chemical and physical properties of the slag. The work outlined below presents a study of the CaF2-CaC2 system intended to provide sufficient data to allow an estimate of the importance of this system to electroslag remelting and welding practice. However, we should indicate at this point that there will be other processes, e.g., heat treatment, flux cleaning of castings, fused salt electrolysis, and so forth, where alkaline-earth halide fluxes are in contact with carbon, graphite, or carbides, and where halide-acetylide solutions must be taken into account. EXPERIMENTAL 1) Structural Studies. In view of the difficulty ex-perienced in handling CaC2 prepared from calcium turnings and propane gas at 700°C, it was decided to use solutions prepared directly in the equilibration apparatus, Fig. 1. The starting materials were: a) Ni-Ca-C alloy, prepared by adding calcium to liquid nickel held under calcium fluoride in an induction-heated graphite crucible; b) calcium fluoride, prepared by fusing calcium fluoride powder (British Drug House "EXTRA PURE") calcium fluoride in an induction-heated graphite crucible, in air, followed by electrolysis between graphite electrodes at 1 amp cm-2 density, for 10&apos; coulombs per g CaF2. This procedure decomposes the CaO produced by hydrolysis during the fusion step, replacing it by CaC2; Ca2+ + 2e-Ca*(l) Ca*(l) + 2C(gr)-(CaC2)caF2 O2- -2e-O*(g) O*(g) +C(gr)-CO(g) This results in a composition of between 2 and 5 wt pct CaC2 in CaF2. Fifty grams (in lumps) of this material were placed in a graphite crucible, together with Ni-Ca-C alloy (averaging 20 wt pct Ca), and the equilibration apparatus assembled. The alloy reacted with the crucible at high temperature to give CaC2, which dissolved in the calcium fluoride solution to give the desired composition. Cooling curves were plotted manually for these liquids, with rapid stirring and CaF2 seeding to minimize supercooling, and using a Pt/Pt 13 Rh thermocouple calibrated on the freezing points of nickel and copper. This gave a reproducibility of ±0.l°C. and an absolute accuracy of the thermocouple of ±l°C. An example curve is shown in Fig. 2, with the CaF2 end of the binary system in Fig. 3. The CaF2-CaC2 ingots were crushed, under dry nitrogen, and sampled for chemical analysis and X-ray examination. Analytical details are given in the Appendix. Powder diffraction data indicated that the only phases present in all samples examined were calcium fluoride and tetragonal (Types I and 111) calcium acetylide,4 with no evidence of solid solutions or compound formation. 2) Thermochemical Studies. The apparatus used to obtain activity data on CaC2 in these systems is shown in Fig. 4. It consists of an arrangement whereby the graphite crucible and its contents (CaF2-CaC2. Ni-Ca-C) can be rapidly cooled without exposure to air. Trial experiments to determine an equilibration time by ap-

Jan 1, 1969

By B. B. Rath, Hsun Hu

In wedge-shaped bicrystals of zone-refined aluminum it is observed that (111) pure tilt boundaries migrate under the driving force of their own inter-facial free energy. The boundary velocity is a power function of the driving force. The driving force exponent decreases with decreasing angle of misorien-tation. For example, at 64O°C, the exponent decreased from 4.0 for a 40 deg to 3.2 for a 16 deg tilt boundary. An evaluation of the driving force acting on the boundaries during their motion indicates that for low driv-forces, up to about 2 x l03 ergs per cu cm, the velocity is relatively independent of misorientation, whereas at higher driving forces a 40 deg tilt boundary exhibits the highest velocity. The measured activation energy for boundary migration approaches that for bulk self-diffusion at low driving forces, decreasing from 33 to 27 kcal per mole as the driving force is increased from 1 x l0 to 5 x l03 ergs per cu cm. These results are compared with current theories of grain-boundary migration. In previous experimental studies of grain boundary migration the driving force has been limited to a difference in stored energy across the boundary. This stored energy has been introduced into the crystal either by prior deformation1-3 or by grown-in lineage structure. A part of the energy stored in the deformed crystal is released by recovery either prior to or concurrently with grain boundary migration, thus introducing an uncertainty as to the magnitude of the driving force responsible for grain boundary migration. The grown-in lineage structure, though thermally stable during annealing, neither provides conditions under which different levels of energy may be stored in the imperfect crystal nor provides a control of orientation difference across the migrating boundary of a growing grain. Furthermore, because of variation in the lineage structure, it is difficult to determine accurately the energy stored in the imperfect crystal. Several investigations of grain boundary migration during normal grain growth have also suffered from difficulties in estimating the driving force because of uncertainties in the principal radii of curvature.~ In the present investigation the velocity of pure tilt boundaries in zone-refined aluminum bicrystals of selected orientation (40, 30, and 16 deg around the [Ill] tilt axis) has been measured in the absence of a dislocation density difference across the moving boundary, thus eliminating the previous experimental difficulties. The driving force for boundary migration is derived from a gradient of the total interfacial free energy of the migrating boundary in wedge-shaped bicrystals. A similar method was attempted by Bron and Machlin in a study of grain boundary migration in silver. However, they found that one of the crystals was deformed and consequently the motion of the boundary was partly due to a difference of stored energy across the boundary. The observed behavior of boundary velocities as affected by the driving force is examined in the light of the predictions of the current theories of grain boundary migration.7"10 The effect of boundary misorientation on velocity is compared with the theory of " which is based on a dislocation core model for high-angle boundaries. EXPERIMENTAL METHOD Seed-oriented bicrystals of zone-refined aluminum, 2.5 cm wide, 0.5 cm thick, and 12 cm long, containing tilt boundaries with a common (111) axis, were grown from the melt in the direction of this axis. Spectro-graphic analysis, reported earlier,&apos;&apos; indicated the purity of the crystals to be 99.999+pct. Three such bicrystals containing 16, 30, and 40 deg tilt boundaries were used. Wedge-shaped specimens were prepared from these bicrystals by spark cutting followed by electrolytic polishing. The angle of the wedge was usually 40 deg and the specimens were usually 0.25 cm thick. The intercrystalline boundary was located within 0.2 to 0.5 cm from the tip of the wedge. Fig. 1 shows a section of an oriented bicrystal containing an outline of a wedge-shaped specimen. The crystallographic directions shown in Fig. 1 represent the orientation of one of the crystals (the larger section of the bicrys-tal); the orientation of the other crystal differs only by rotation around the common [lil] axis. The parallel faces of the wedge always corresponded to the common (171) planes in both crystals, whereas the orientation of the side faces varied, depending on the misorientation angle. The bicrystal orientations were determined

Jan 1, 1970

By F. L. Bosqui

A. L. BlomFIeld, Denver, Col. (communication to the Secretary.*) — Mr. Caldecott says on p. 67: "The Dorr thickener shown, while a useful device when crushing with cyanide solution for removing surplus solution from slime pulp prior to air-lift agitation or vacuum filtration, is not adapted to effect as complete a separation of water from settled slime as the ordinary intermittent settlement and decantation." This statement might have passed muster in this country several years ago when. the Dorr thickener was a new device, but its use in hundreds of mills in the United States has demonstrated that as thick a product is being discharged from it as was obtained from the intermittent settling which it has supplanted. • It is interesting to note that recent investigation, especially the work of 11. 6. Coe and G. H. Cleveilger,&apos; in the March Bulletin of the Institute, under the title: Laboratory Method for Determining the Capacities of Slime Settling Tanks, has developed the general theory of settlement and explains the results obtained in practice. Just as free settlement is a function of surface area, so thickening after the zone of free settlement is passed is a function of time. The time required is obtained by the capacity or volume provided in the settler for this thickening zone. Each pulp is a problem in itself, both in regard to free settlement and to time required to reach a commercially finished thickness. Some pulps require 48 hr. and more to reach a density of 40 per cent. solids; others no coarser to the screen test reach a density of 65 per cent.&apos; solids in a fraction of that time. In thickening any pulp a point is reached where the increase in density is so slow as to be commercially unprofitable. When any part of the pulp has reached this point it should pass on for treatment—its place in the thickener should be occupied by pulp which has not yet reached the commercial limit. By doing this the whole volume of the settling tank is kept in active use. Thus the continuous thickener keeps the whole tank at work to its commercial limit, while the intermittent settler has much of its volume occupied at times by pulp which is either quite finished thickening or at least thickened past the commercial point. The mechanical efficiency of the continuous thickener can be the only argument for limiting this statement. In my own experience I have never

Jan 1, 1916

By E. V. Kleber, V. F. Novy, R. C. Vickery

The constitutional diagram for the gadolinium-cobalt system has been determined. Seven intermetallic compounds have been found at compositions corresponding to the follwing gadolinium-cobalt ratios: 3:1, 1:1, 2:3, 1:2, 1:3, 1:4, 1:5. The GdCor compound has a congruent melting point above 1600°C. whereas the remaining compounds melt incongruently. Eutectics exist at 16 wt pct Co and 84 wt pct Co, with melting points of 620° and 1260°C, respectively. PREVIOUS papers&apos;" have recorded constitutional data for systems of gadolinium with iron and nickel. This paper presents data obtained on alloys of gadolinium with the remaining 3d transition element-cobalt. voge13 found that cerium forms, with cobalt, the intermetallic compounds; Ce3Co, CeCo, CeCo2, CeCo3, CeCo4, and CeCo5 Other workers4-&apos; found the 1:2 compound in this series to exist in a C-15 (face-centered cubic) structure and the 1:5 compound to exist in a hexagonal crystal system. Comparison of earlier data with that now reported will be made subsequently. EXPERIMENTAL Methods of alloy preparation, annealing procedures, and experimental techniques have been previously reported.&apos; The cobalt content of alloy specimens was determined volumetrically. RESULTS Microstructure—The alloy containing 10.5 wt pct Co corresponds closely to the composition of the first intermetallic compound Gd3CO. In Fig. 1 the microstructure is essentially single phase composed of Gd3Co which formed peritectically. The globular areas are remnants of the peritectic reaction which did not quite go to completion. A eutectic occurs between Gd3Co and the next higher compound GdCO, which is followed by a series of peritectic compounds. Fig. 2, an arc-cast alloy containing 20.2 wt pct Co, shows large primary crystals of GdCo etching either white or black (depending on crystallographic orientation), embedded in the eutectic. Similarly, in Fig. 3 at 31.2 wt pct Co, a compound, probably GdCo3, has separated from the melt. Subsequent peritectic reactions were almost completely by-passed as the alloy cooled, the residual liquid freezing as a fine eutectic. In the 47.5 wt pct Co alloy, Fig. 4, the high melting point compound, GdCO4, has solidified as massive, white-etching grains, which reacted with the liquid to form GdCo3 as the second phase. The microstructure of an arc-melted alloy containing 60.5 pct Co is complex, Fig. 5, and presents some difficulty in interpretation. The grey etching matrix is probably primary GdCO4. The dappled phase represents grains of GdCO5 which have separated from the melt on cooling. The discrete spots in this phase are eutectic liquid. Small light etching crystallites are probably GdCO5 formed by the incomplete high-temperature peritectic reaction. GdCO4 is retained in arc-melted specimens containing 70.5 wt pct Co, Fig. 6. White areas of this compound are held in a matrix of GdCO5 the appearance of which is mottled slightly by inclusions of the second eutectic in this system. The development of the spheroidized eutectic at high cobalt contents is depicted in Fig. 7 (80.3 wt pct Co) in which the white massive crystals are GdCO5 compound. Further development of this eutectic is seen in Fig. 8, the primary white phase here being pure cobalt. Thermal Studies—Differential thermal analyses and melting point determinations have yielded the data shown in Fig. 10. The high gadolinium eutectic, indicated by microscopy, was confirmed at about 16 wt pct Co, melting at 620°C . A eutectic also occurs at about 84 wt pct Co melting at about 1260°C. The thermal arrests at 8803 960°, 1060; and 1210°C,

Jan 1, 1962