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By L. W. Eastwood

The structure of eutectics has been studied by a number of investigators, and the complexity of the structural relationship of the components has been agreed upon, especially that of the "eutectic colony," type III of Portevin's1 classification. This paper does not attempt to alter the present classifications of eutectics; rather, it discusses the relationship between the macrostructure and the microstructure of the copper-cuprous oxide eutectic, and describes in detail the mechanism of the formation and the structure of the eutectic. Further, throughout the entire discussion it attempts to point out certain misconceptions in regard to the interpretation of the observed structure of the copper-cuprous oxide eutectic, one of the so-called "eutectic colony" types, and to correlate as much as possible the work done by the writer with that done by other investigators. Of the three types of eutectics listed by Portevin,2 the eutectic colony type has presented the greatest difficulty in interpretation. Although the copper-cuprous oxide eutectic is typical of the eutectic colony type in appearance, it may not be truly representative because the copper forms about 96 per cent of the eutectic and the cuprous oxide about 4 per cent. The interpretation of the origin and structure of the "eutectic colony" given here is strictly limited, therefore, to the copper-cuprous oxide eutectic. Macrostructure Fig. 1 shows the macrostructure of the eutectic at 3 diameters, the melt having been chill-cast into an iron mold, the resulting specimen sawed into two parts and the section polished and etched with the usual mixture of hydrogen peroxide and ammonium hydroxide. This specimen contains 0.48 per cent oxygen and is only slightly hypereutectic. If such a melt is allowed to cool slowly, large macrograins will form without the columnar structure of Fig. 1 and the well-known phenomenon of liquation will occur, forming copper oxide dendrites at the top and copper

Jan 1, 1934

By Henry C. Freeman

During the early period of the construction of the Illinois and Michigan Canal, about 1838, in excavating for the canal, where the present town of Utica stands, hydraulic limestone was discovered, and its value was recognized. A kiln for calcining and a mill for grinding were erected, and the cement was used in the construction of the locks of the canal. This property was subsequently bought by the present owner, Mr. James Clark, and the work has been continued to the present time in much the same primitive manner as it was begun. The bed is exposed in the Illinois River valley by stripping off a few feet of the covering rock. It is from 4 feet to 6 feet 9 inches thick, and nearly level, dipping gently to the northeast. The Utica Cement Company's establishment, which is two miles west of Utica and two miles east of La Salle, was an outgrowth of the Illinois geological survey. The writer was in charge of the district which included La Salle county, and, in working out the details of the geology of that county, discovered, below the Utica bed, another workable hydraulic limestone, which makes its appearance in the northern bluff of the Illinois River valley, rising above the water level at the point where the company's works are established. This cement group, of which there are several thin beds, lies just below the St. Peter's sandstone, with a few feet intermediate of transition-rock, which appears to represent the Calciferous, and is exhibited in place, in concretionary form, at the top of the bluff. The hydraulic beds are very regular, and the one worked by the company is 10 feet thick; or, speaking more definitely, there are two beds, separated by 18 inches of sandstone, lying about two feet above the bottom, and the two beds are worked as one, the sandstone being first cut out and removed, to prevent mixture. In 1869 I was invited to join with a company, and to take charge

Jan 1, 1885

By AIME AIME

THE convention which met in Washington at the call of the Joint Conference Committee was called to order at ten o'clock on Thursday morning; June 3, by Richard L. Humphrey, temporary chairman, member of the American Society of Civil Engineers, who made a brief statement of the reason for the meeting. Lieut. Col. Charles W. Kutz, Corps of Engineers, U. S. A., and Engineer Commissioner of the District of Columbia, then welcomed .the engineers composing the convention on behalf of the District of Columbia and, the Washington engineers. Although an elaborate program had been prepared on which were many well-known speakers on interesting and important topics, , it was voted to intersperse this to fill in the usual and unavoidable hiatuses in the business program of such a convention[ Calvert Townley, president of the American Institute of Electrical Engineers, was elected permanent chairman, and J. C. Hoyt, of Washington, was elected secretary of the convention. The following committees were appointed: Consti¬tution and by-laws, Richard L. Humphrey, chairman; resolutions, Philip N. Moore, chairman; and program, F. H. Newell, chairman. Then, Gardner S. Williams, member of the, A. S. C. E. and the Grand Rapids Engineering Society of. Grand Rapids, Mich., and one-time member of the American Association of Engineers, offered the following resolutions:

Jan 1, 1920

By J. L. Humphrey

The origin of roof bolting is obscure, but is believed to have begun some 40 years ago in the mines of St. Joseph Lead Co. in southern Missouri. It was not until after World War II, and more particularly after 1949, as a result of the concentrated effort of the USBM, that roof bolting attracted widespread interest. It is estimated that at the end of 1954, 26 pct of all bituminous coal mining in the U. S. was being done under roof bolts. Those mines alone use nearly 2,000,000 roof bolts per month, according to USBM statistics. Uses in metal mines are increasing rapidly, as confidence and knowledge grow. The application has found equal success in other fields, such as tunneling work for dam and waterway construction and right of way maintenance on highways and railroads.

May 1, 1956

By Charles H. Fulton

THE Engineering Education group began its sessions Tuesday morning, Feb. 16, as a Committee and wound up the day as the Institute's fifth " Division." C.II. Fulton presided. The first paper for discussion was entitled "Teaching Management in Engineering Schools,"' by Eugene McAuliffe, president of the Union Pacific Coal Co., space for which may be found later in these pages. In it, Mr. McAuliffe argued that an engineering student should be taught the knowledge of men, much as a medical school teaches surgery. He then went on to indicate, out of the wealth of his administrative experience, the problems an executive needs to be equipped to handle, and said that every student engineer should look on himself as a potential manager.

Jan 1, 1932

By Lord Marley

ACTIVE participation by the United States in the war acted as a stimulant on the Annual Institute Meeting in New York rather than a retardant as feared. Attendance was about 10 per cent under the all-time high reached last year, but considering the number of men who could not possibly come because of active military service and the additional number who are devoting their whole time and effort to turning out vital war materials, the registration was really greater than might have been expected. But all in all the Institute put on a show that taxed the capacity of the Engineering Societies Building as well as the capacity of the visitors to find time to attend everything that promised to be of interest.

Jan 1, 1942

By L. Kaufman

An equation is derived relating AF a", the difference in free energy between austenite and martensite, to temperature and composition in the iron-chrmnium and iron-chromium -nickel systems. This equation is used to calculate at M,for low-carbon stainless steels. A method for utilizing the energetic equations to calculate M, in stainless steels is suggested. In addition, an explanation is given for the anomalous effect of chromium in forming a y loop concurrent with the lowering of M, in iron-base alloys. It has been demonstrated that the effect of alloying elements on the Ms temperature is strongly dependent upon the influence of the alloying element on the thermodynamic properties of the y and a phases. Notwithstanding the fact that alloying elements affect the Ms temperature by changing the lattice parameters, elastic constants, and inter-facial energies of the a and y phases, their primary role is a thermodynamic one. Thermodynamic analyses have been presented for the iron-carbon'-4 and iron-nickele systems in which equations are derived for Fa and FY, the free energies of the b.c.c. (or b.c.t.) and f.c.c. phases. These equations, which can be obtained with the aid of the equilibrium diagrams, can be used to help predict the Ms vs composition curves. This paper deals with a calculation of the thermodynamic properties necessary to compute AFffLY for iron-chromium alloys. In view of the lack of direct information concerning the activity of chromium in the a and y phases of iron, the regular solution approximationa,g was utilized to bridge the gap. After the necessary equations were derived for the iron-chromium system they were used to calculate AFff— Y for stainless steels by combining them with the previous results obtained for iron-nickel alloys. The results of these calculations offer a means of rationalizing the anomalous behavior of chromium in iron-base alloys. The latter depends on the regular solution approximation in contrast to the explanation offered by zener , which is based upon the "magnetic specific heat effect." THERMODYNAMICS OF THE IRON-CHROMIUM SYSTEM If y represents the atomic fraction of chromium in an iron-chromium alloy, then the free energy of the b.c.c. phase Fa, the f.c.c. phase FY, and the difference in free energy between the f.c.c. and b.c.c. phases of the same composition are given through [3] and Fmy represent the free energies of mixing of the a and y phases; while @era -' and uFea 4Y represent the difference in free energy between f.c.c. and b.c.c. chromium and iron respectively. The values of AEFe0ff4Y in the temperature range between 0" and 900K ( .

Jan 1, 1960

By Wm. A. Haven

As soon as the likelihood of American participation in the war was established, and in spite of the fact that we can produce almost as much as all other countries combined, the demand for prompt deliveries of iron and steel products from American factories began to exceed their utmost capacity, and, after fifteen months of practically full operation, has continued to do so. Therefore, it would seem worth while to review some of the aspects of the supply and demand for steel as well as the efforts that are being made to bring them into balance. It is still being debated as to whether the situation should be defined as a real shortage that will persist through the emergency period or as a temporary one than can be relieved by less drastic measures than a Government-sponsored program of expanding existing plants and building new ones.

Jan 1, 1942

By Joseph W. Richards

THIS method of briquetting flue-dust, or flue-dust mixed with fine ores, or, in a few exceptional cases, coke-dust, has come into large commercial use in Europe, and a small plant is already in operation in the United States. It promises to become of such great importance to the iron industry of the United States that the following description will certainly interest the majority of our pig-iron producers. Discovered in 1908, the process rests upon the observation of Dr. Schumacher that blast-furnace flue-dust, while possessing of itself no binding or cementing properties, acquires strong cementing properties if mixed with a very small amount of certain salt solutions, the amount of which is so small that the resulting cementation appears to be rather by catalytic action of the salts added than by the mass-action of such chemicals. To be more specific, fresh blast-furnace flue-dust mixed with from 5 to 10 per cent. of its weight of magnesium chloride or calcium chloride solution-that is to say, with from 0.25 to 2 per cent. of its weight of magnesium chloride or calcium chloride-acquires the property of setting within a short time, from 15 to 60 min., and forming a hard cemented briquette. Alkaline solutions appear to have no action such as described, and they even interfere, if present, with the action of the magnesium and calcium solutions. When treated in this way the flue-dust briquette sets very hard, apparently from pure excess of cementing- and setting-power. It is, therefore, possible to . mix with the flue-dust a considerable proportion of inert ore or like material, which has no setting-power by this process, and thus to make a compound briquette containing large quantities of ore mixed with flue-dust, but in which the flue-dust may be regarded as the cement or binding-material. A particularly strongly cementing flue-

May 1, 1912

By Paul M. Tyler

HISTORICAL concepts of the economics of the glass-sand industry are changing rapidly. The greatly expanded demand for glass containers combined with higher freight rates on raw materials and manufactured products have induced a migration of glass factories toward densely populated centers and the creation of new standards of place value for sub- standard sand deposits. This migration has been facilitated by the construction of pipelines to bring cheaper natural gas and liquid fuel to large cities and may be further speeded by the adoption of modern mineral dressing methods to permit economical utilization of local raw materials. Our national resources of naturally high-grade 1 silica sand are abundant, but most of the best de- posits are situated so far from large centers of population that it now costs $3.00 to $5.00 a ton to carry the sand from the mine to the optimum site for a 1 factory making beverage bottles, scientific and electrical glassware, and miscellaneous blown and pressed ware for local markets. It follows that on the basis of freight savings alone it may be economical to use material from inferior deposits closer to the factory even though the f.o.b. cost of mining and treatment may be much high

Jan 1, 1950

By AIME AIME

PRACTICALLY all the Section delegates as well as a sprinkling of Institute officers and mere members were on hand for the annual business meeting of the Institute on Monday afternoon of the Annual Meeting. President McAuliffe presided, with C. H. Mathewson as associate chairman. Americo Albala was first called on to discuss the work of the Pan American Institute of Mining Engineering and Geology. C. Will Wright said that the need for such an organization was evident, and a resolution was passed asking the incoming President to appoint a committee to investigate cooperation with that body, of which Mr. Albala is executive secretary.

Jan 1, 1943

By John A. Church

Jan 1, 1880

By T. Sterry Hunt

Jan 1, 1891

By Noel Jarrett, Allen S. Russell, Bernard M. Starner, Stanley C. Jacobs

A process has been developed to refine high-grade commercial aluminum to 99.99 pct purity. This enzploys precipitating titanium, vanadium, and zirconiu~ as borides. The upgraded liquid is partially crystallized under conditions that prevent massive freezing. The resulting crystals are compacted and washed free of adhernig impure liquid aluminum by melting the top crystals while draining off the liquid. Finally, the bottorn portion of the crystal bed is melted and removed as the pure product. Leakage from the crystallizat~on vessel is prevented by a layer of alumina granules that are not wetted by the aluminum. ALUMINUM of 99.99 pct purity is desired in a variety of applications. These include electrolytic capacitors, catalyst carriers, decorative trim for automobiles, aluminum powder, and high-strength alloys. This market was for many years filled by refining commercial-purity aluminum in a three-liquid-layer electrolytic cell of the type originally proposed by Hoopes. To meet the expanding need for lower-cost high-purity aluminum, a refining process based on chemical precipitation and fractional crystallization was developed. The availability of this super-purity metal was announced in November 1961, and three patents1-3 relating to the process were issued in 1965. An alternate process, comprising continuous fractional crystallization of a portion of a liquid-aluminum feed stream under conditions of strong agitation at the surface of the growing crystals, was published by Dewey4 in 1965. Earlier proposals by Larsen 5 and by Regner6 also emphasized the advantage of rapid agitation of the melt in the region of the crystallization zone. johnson 7 more recently proposed extracting purified aluminum from an alloy by mixing crystals of pure aluminum into the molten alloy, allowing them to grow, and removing the pure aluminum as by casting. Aamot's 8 recent patent describes a freeze refining process that involves controlled partial freezing against cooled moving retort walls. The Alcoa process to produce high-purity aluminum is schematically described in Fig. 1. Relatively pure aluminum is treated with boron in a furnace (a) to precipitate high melting point impurities, the supernatant liquid is transferred to a crystallization vessel (b), the liquid is partially crystallized with mechanized "tamping" (c), the remaining impure liquid is tapped out and the crystal bed partially and directionally re-melted to wash the underlying crystals (d), and the balance of the crystals is melted and withdrawn as high-purity aluminum (e). PRINCIPLES OF FRACTIONAL CRYSTALLIZATION Commonly encountered impurity elements form two types of systems with aluminum. Titanium, vanadium, and some other transition elements in periodic groups IV, V, and VI are the high melting point impurities. Initial solidification of aluminum containing small percentages of these elements will produce solid markedly enriched in them at temperatures slightly above the freezing point of high-purity aluminum. Most other elements, such as silicon and iron, produce eutectic type reactions with aluminum. In this case the first solid formed on initial solidification at temperatures slightly below the freezing point for high-purity aluminum is markedly depleted while the remaining liquid is enriched in these elements. The equilibrium change in composition during solidification of aluminum contaminated with silicon, iron, or titanium is illustrated in Fig. 2. Here, for clarity, the temperature scale is expanded beyond the

Jan 1, 1968

By Thomas Leonard Watson

I. HISTORICAL. BARITE has been mined for many years in various parts of Virginia, probably the earliest mining-operations being in Prince William county, within 600 ft. of the Fauquier county line, about 4 miles south of east from Catlett, a station on the Southern Railway. It is claimed that the mineral was mined here as early as 1845. Mining-operations in Campbell and Pittsylvania counties in the Piedmont region, and near Marion in Smyth county, in the southwest Virginia Valley region, were begun about 30 years ago. The mining and milling of barite on a commercial scale in Tazewell and Russell counties are more recent, and commenced about 15 years ago. II. GEOGRAPHICAL AND GEOLOGICAL DISTRIBUTION. Barite occurs in many counties in the State, as shown in Fig. 1, but the industry has been confined to only a few of them. Its occurrence is noted in two of the three major divisions of the State-namely, the Piedmont region east of the Blue Ridge, and the Paleozoic area west of the Blue Ridge. In the Piedmont region the mineral has been mined in the following counties:, Bedford, Campbell, Louisa, Prince William, and Pittsylvania. In the region west of the Blue Ridge, composed of Paleozoic sediments, barite has been mined in Montgomery, Russell, Smyth, and Tazewell counties. Of the counties mentioned, Bedford, Campbell, and Pittsylvania of the Piedmont region, and Russell, Smyth, and Tazewell of the Valley region, have been the principal producers. In 1906, operations were confined to five counties-Bedford, Louisa, Pittsylvania, Russell, and Tazewell-but in the first two counties named there was no production, the work being solely development.

Jan 9, 1907

By Raymond O. Ladoo

FUSED quartz is a glass made by the fusion of nearly pure silica. Some confusion in terminology exists but in the trade today "fused quartz" generally refers to the perfectly transparent colorless product made from rock crystal whereas "fused silica" is a white, translucent product made from silica sand. Vitrified silica is the term preferred by purists for all quartz glass, but it lacks the definiteness of -the trade terms. Since the raw materials, methods of production, and properties of the finished products arc different for the two types, the trade terms are preferred. As fused quartz is amorphous, it-physical properties differ greatly from those of quartz crystal. Lacking crystallographic directions and having no piezo-electric properties, fused quartz. of course, has no value for the making of radio oscillator plates; but it does have other valuable and unique properties. Perhaps the 'best known and most useful properties are its extremely low coefficient of expansion and its ability to transmit short-wave ultraviolet radiant energy. Crystal quartz not only has an aver-

Jan 1, 1947

By K. E. Nelson

The effect of thorium and zinc variations on the strength and 100-hr creep characteristics of Mg-Th-Zn-Zr alloys was investigated. Optimum resistance to creep at 650° and 700°F are attainable within a certain range of thorium and zinc contents. This range does not conform to that which develops maximum tensile properties. RAPID advances have been made during the last few years in the development of magnesium alloys for elevated temperature applications demanding high resistance to creep. The beneficial effect of rare-earth metals on the creep resistance of magnesium alloys has been emphasized by a number of publications1-13 and such alloys are now in commercial production. The use of thorium as an alloying ingredient in magnesium was mentioned by McDonald and also in two Alien Property Custodian patent applications.10,17 The initial observation of Sauerwald that thorium contributes still higher creep resistance to magnesium than is attainable with rare-earth metals has recently been substantiated.'" " In fact, it has been demonstrated that the useful temperature range of magnesium alloys is appreciably extended by the use of thorium. In all cases, it was observed that zirconium must be included in the alloys in order to render them fine grained and more readily castable. Several recent publications:2-27 indicate that a still further improvement in creep resistance and a further extension of the useful temperature range can be realized by the addition of zinc to alloys. The primary purpose of this paper is to present the results of a comprehensive study of the effect of zinc on the strength and creep characteristics of Mg-Th-Zr alloys. Compositions covering the range of thorium content from M to 6 pct and zinc content from 0 to 5 pct have been investigated. The creep characteristics at 650" and 700°F reported in this paper are based on results of tests of 100-hr duration. It is appreciated that creep tests of 100-hr duration might not yield adequate data for design purposes for parts with much longer expected life. However, for the purposes of the present discussion, it is felt that the combination of stresses and temperatures used in the 100-hr creep tests have yielded a clear representation of the compositional variation of creep resistance at the temperatures investigated. Creep tests of 1000-hr duration are now in progress on a few of the most promising alloys. Preparation and Testing of Alloys The alloys studied in this intensive investigation were prepared in 25 lb capacity mild steel crucibles. The thorium, zinc, and zirconium were alloyed and poured as described in earlier publications The thorium was introduced into the melt in the form of a Mg-Th hardener," the zinc added in the metallic form, and the zirconium alloyed in the form of the commercial hardener containing magnesium and 30 to 50 pct Zr.10, 26 Fluxing practices for melting and refining were the same as for magnesium-rare-earth metal-zirconium alloys. The melts were sampled for analytical determinations and poured into separately cast 1/2 in. diameter standard tensile bars. The test bars were given a precipitation treatment of 16 hr at 600°F in laboratory furnaces. It has been shown by other tests that a high temperature solution treatment followed by an aging treatment is unnecessary for the development of optimum properties in Mg-Th-Zn-Zr alloys. The selection of 600°F as the aging temperature was based on an attempt to achieve metallurgical stability without coalescence of the undissolved phases and the attendant loss in strength. The thorium, zinc, and zirconium contents of each melt were determined chemically. The zirconium contents are reported in two parts, "soluble" and "insoluble," referring, respectively, to the portions present in the alloy which are soluble and insoluble in dilute HCl acid. Distinction is being made between these two components of the zirconium content in the alloys because it has been found that only that portion of the zirconium content which is soluble in dilute inorganic acids affects the structure and properties of the alloys. The usual impurities consisting of copper, iron, manganese, and nickel were determined spectroscopically. The analysis for each melt is listed in Table I. A description of the methods of tension and creep testing has been detailed in earlier papers. The tests were performed with the cast skin re-

Jan 1, 1954

By H. C. Babbitt

The Effect of Arsenic.—A question involving the temperature of precipitation of ammonium phospho-molybdate, which was brought to my attention some time ago, led to the following experiment :*

Jan 1, 1893

By L. S. Darken, H. A. Wriedt

The equilibria at 1 atm total pressure and 600° to 1300°C (1112° to 2372°F) between gas mixtures with various partial pressures of the reactive constituents (principally sulfur dioxide, carbon dioxide, water vapor, oxygen or carbon monoxide, and hydrogen) and coexisting solid phases (groups variously including calcium oxide, calcium carbonate, calcium sulfide, calcium sulfate, iron, ferrous sulfide, and the iron oxides) are examined. Tables and charts show the combinations of temperature, oxygen activity, and carbon dioxide partial pressure under which the various groups of the solid phases coexist and the corresponding sulfur dioxide pressures. In the presence of calcium sulfide, calcium sulfate, and calcium oxide, the partial pressure of sulfur dioxide has a peak value at each temperature which increases from 101 atm at about 800°C (1472°F) to 1 atm at about 1200°C (2192°F). With water vapor present, hydrogen sulfide may predominate among gaseous sulfur compounds, particularly at low temperatures and oxygen activities; under all other circumstances considered, sulfur dioxide is the dominant gaseous sulfur-bearing species.

Jan 1, 1974

By R. D. Schoone, J. T. Michalak

Recovery, recrystallization, and texture development of a cold-rolled aluminum-killed steel have been studied during simulated box annealing. Two different initial conditions existed prior to cold rolling: 1) essentially all of the nitrogen in solid solution and 2) most of the nitrogen precipitated as AlN. The combined effect of nitrogen and aluminum in solid solution before annealing was to inhibit recovery and sub-grain growth at temperatures above about 1000°F and to raise the recrystallization temperature range on continuous heating at 40°F per hr from 1000"-1050°F to 1065"-1085°F. For the material with nitrogen and aluminum initially in solution there was an inhibition in the nucleation of the (001) [110] texture component and an enhancement of the (111) [110] texture component. The differences in annealing behavior mzd texture development are attributed to preprecipitation clustering of aluminum and nitrogen at subboundary sites developed by prior cold working. THE annealing of cold-worked aluminum-killed steels has been the subject of numerous investigations.'-'2 These studies have been concerned with kinetics of recrystallization, with microstructure and texture development, and with the individual and combined effects of composition, thermal history prior to cold rolling, and heating rates during subsequent annealing. It has been shown that the inhibition of recrystallization, and the development of the pancake-shaped grain and recrystallization texture characteristic of aluminum-killed steels, can be associated with the precipitation of A1N particles during a recrystallization anneal involving heating rates in the range 20" to 80°F per hr. If the AIN is precipitated before cold rolling or if more rapid heating rates are employed, the cold-rolled steels recrystallize more rapidly to an equiaxed grain structure and texture comparable to that of rimmed low-carbon steel. The retardation of recrystallization, the development of the elongated grain structure, and the pronounced (111) texture have been attributed to: 1) precipitation of A1N at prior cold-worked grain boundaries to form a mechanical barrier to grain boundary migration;' 2) precipitation on the boundaries of the growing recrystal-lizing grains as well as on cold-worked grain boundaries;'" and 3) preprecipitation clustering or precipitation on subboundaries to retard recovery, nucleation, and growth. The present study was undertaken to study in more detail recrystallization and texture development during commercial box annealing of cold-rolled aluminum-killed steels. Comparison of the annealing be- havior after cold rolling, for two different conditions prior to cold rolling, was made in an attempt to define more clearly the role of aluminum and nitrogen in forming the recrystallization texture. A) MATERIAL AND PROCEDURE The material used in this investigation was a commercial low-carbon aluminum-killed steel which was hot-rolled with a finishing temperature of about 1565"F, then coiled at about 1020°F. The composition, in wt pct, was: 0.050 C, 0.30 Mn, 0.007 P, 0.019 Si, 0.03 Cu, 0.02 Ni, 0.02 Cr, 0.045 Al, and 0.004 N. Two 4.5 by 13 by 0.078 in. sections were cut from the center section of a hot-rolled panel and one of these was reheated to provide two different conditions prior to cold rolling: low AlN: as commercially hot-rolled, with aluminum and nitrogen in solid solution; and high AlN: as commercially hot-rolled, then reheated at 1300°F for 3.5 hr to precipitate most of the nitrogen as AlN. ~etallc&a~hic examination indicated that the reheating did not change grain size nor carbide distribution (some spheroidization of pearlite was noted). Texture analysis at half-thickness level showed that both sections had the same substantially random as-hot-rolled texture. The results of check chemical analysis of each sample are given in Table I. Both sections were cold-reduced 65 pct on a laboratory rolling mill to a final thickness of 0.027 in. Cold rolling, in one direction only, was in the direction of the prior hot rolling. Specimens 1.0 by 1.25 in. were cut from the cold-rolled sheets and given a simulated box anneal in an atmosphere of 2 pct HZ-98 pct He. Specimens were heated at a constant rate of 40°F per hr from room temperature to various temperatures in the range 750" to 1300°F and cooled immediately by withdrawal to the water-cooled end of a tube furnace. The temperature in the 6-in. uniform hot zone of the furnace was controlled within 3"F. Selection of the individual specimens was made to give a random distribution of annealing temperatures with respect to location in the cold-rolled sheet. At least two specimens of each condition were annealed to the same temperature and smaller specimens for light microscopy, transmission electron microscopy, and X-ray studies were prepared from each of these. Rolling-plane sections for each of these studies were taken at half thickness. Light microscopy and transmission electron micro-

Jan 1, 1969