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By H. E. Elliott, R. S. Busk, A. T. Peters

ONE of the problems of the fabricator of metals and alloys is the propensity of some composition ranges toward abnormal grain growth during certain stages of fabrication. In this respect magnesium alloys are no exception among alloys. Fortunately, convenient foundry control methods have been developed by which the abnormal grain growth possible in certain magnesium-alloy castings can be suppressed. An unusual characteristic of magnesium alloys, however, is that castings of some composition ranges are subject to local grain growth during heat-treatment without the necessity of intentional mechanical stressing of the part prior to heat-treatment. This effect occurs only under certain critical casting conditions, and only in certain alloys of greater than about 8.5 per cent aluminum content, such as C alloy (Mg, o per cent Al, 2 per cent Zn, 0.2 per cent Mn) and G alloy (Mg, i0 per cent Al, 0.2 per cent Mn). The first observation of this phenomenon in cast magnesium alloys occasioned much surprise, since it is not observed in other metals. Jeffries and Archer' have stated that "the grain size of cast metals, provided they have not been plastically deformed, cannot be changed by heating below the melting point." The study of the conditions leading to abnormal grain growth in cast magnesium alloys, and of the mechanism of this phenomenon, has led to some very interesting observations. Perhaps the most significant of these was the observation that stresses originating from cooling contraction in magnesium-alloy castings are the only stresses necessary, under certain conditions, to cause local recrystallization and subsequent grain growth in the casting during heat-treatment. of abnormal local grain growth was a definite problem in the production foundry on C alloy sand castings. Illustrated (Fig. r) is a picture of a casting scrapped because of this defect. A mottled effect is produced in coarse-grained areas by suitable etching solutions. The properties of metal in the affected area are much impaired by such grain coarsening. Ultimate tensile strengths of half the normal value have been measured in metal of this nature. In this paper are described the techniques that have been developed by The Dow Chemical Co. for studying, and in large measure solving, this production problem. Also discussed are studies of the mechanism by which excessive grain coarsening occurs, and the fundamental conditions that produce this effect. The abnormal grain growth discussed in this paper will be referred to as "germination," since this term has been defined' as any process leading to an abnormally coarse grain size. This paper deals only with abnormal local grain growth that may occur during the solution heat-treatment of certain magnesium-alloy castings, as dis-

Jan 1, 1945

Jan 1, 1961

By Howard N. Eavenson

An analysis of the bituminous coal situation by an authority who traces the production, mining, safety, markets and labor trends in comparison with other fuels.

Jan 2, 1950

By G. A. Vissac

The drying of fine coal involves special techniques, which are discussed and analyzed. Types of dryers employing these techniques are described. Calculations are presented for new methods of deal ing with the entrained dust that is always present in fine coal drying operations.

Jan 10, 1953

By R. M. Rose, C. S. Tedmon, J. Wulff

It is frequently of interest to study the influence of small quantities of interstitial impurities on the properties of various refractory metals and alloys.

Jan 1, 1964

By Gerald Sherman

Asbestos ore is hard, well intersected by free fissuring but not completely enough to avoid heavy secondary blasting, and is a more valuable ore than usual for caving. These factors have resulted in deviations from standard caving practice in details but not in principles.

Jan 4, 1950

By S. Chander, D. W. Fuerstenau

Hallimond tube flotation, contact angle measurements, electrokinetics, and electrode potential measurements have been used to investigate the natural floatability of molybdenite. The effect of surface pretreatment and the role of hydrogen, hydroxyl, molybdate, and calcium ions on the flotation of molybdenite has been studied. The surface potential of molybdenite has been suggested to be controlled by HMoO[ ] and MoO4= surface species whose properties are strongly influenced by pH. Calcium ions, which appear to be specifically adsorbed, are able to reverse the zeta potential of molybdenite. The experimental results have been analyzed in terms of the Derjaguin model of wettability, namely in terms of van der Waals and electrical double layer interactions and hydration effects at interfaces.

Jan 1, 1973

By Anwar-ul Karim

In one of our recent papers, Cheng, Karim, Langdon, and Dom1 analyzed the creep mechanisms in a Fe-4 pct Si alloy. The experimental results of apparent ac-

Jan 1, 1970

Jan 1, 1879

By Vernon Read, John K. Hayes

Generally speaking, drilling equipment and techniques presently in use are not capable of meeting the complex technical-and economic-requirements of deep core drilling. Drilling to great depths involves increasing risk, time, and money. And it is especially true that costs increase with depth when conventional core drilling methods are used. Introduction of wire-line drilling techniques has been a great boon to deep core drilling, and is rapidly gaining general acceptance. But, in spite of recent progress, there remains a great need to improve productive drilling time and penetration rates, and still maintain high core recoveries.

Jan 1, 1959

By James F. Lewis

The hematite iron ore mines east of the Hudson River are confined to a strip of country ten to fifteen miles wide, commencing on the south, near Fishkill, running northeast through Dutchess County, and striking the southeast corner of Columbia County, extending into Litchfield County, Conn., known there as the Salisbury mines, cropping out again at and near West Stockbridge, Lanesboro, and Cheshire, Mass., also in Bennington County, Vermont. The ores are found in beds or deposits and in veins, with a limestone ledge on one side and slate on the other, from six to thirty feet from the surface. Portions of it are quite solid, called rock ore, but

By John Marshall

THE purpose of this paper is to present to the profession data and experience obtained over a period of 5 years in the operation of 87 shaker-conveyor units, and the production of 2,169,638 tons of run-of-mine anthracite coal. The data are not generally available and should be of interest to those concerned with the operation of anthracite and bitu-minous mines. To simplify comparison, a ton of 2000 lb. of raw run-of-mine coal has been used as the production unit throughout this paper.

Jan 1, 1940

By Wolfgang Pietsch

Pressure agglomeration using tableting machines, roll presses, punch presses, isostatic pressing equipment, extrusion presses, and other less common equipment, represents a large share among commercial applications of size enlargement by agglomeration. The paper attempts to classify and describe the equipment and technology, their development and state of the art, as well as their respective applications, advantages, and disadvantages.

Jan 1, 1977

The second special war meeting of the New York Section was held on Thursday evening, Aug. 23,-preceded by is an informal dime The topic for discussion -was the supply of sulphur and pyrite, the raw materials for the manufacture of one of the most important of till war materials-sulphuric acid. The first speaker was William Young Westervelt, the Institute's representative on the War Minerals Committee. Before taking up the subject of the evening, Mr. Westervelt briefly described the organization and plan of operation of the War Minerals Committee.

Jan 10, 1917

Jan 7, 1950

GENTLEMEN: Submitted herewith are the report of the Treasurer for the year 1940 and reports for the same year of the following standing committees: Admissions, Membership, Pa¬pers and Publications, Mining and Metal¬lurgy (Magazine), Library, and Student Relations. These reports present additional details. MEMBERSHIP For the third year in succession member¬ship reached a new high level for all time, as indicated in the accompanying tabula¬tion in which "Members" includes all categories except Student Associates.

Jan 1, 1941

By R. E. Collom

VARIOUS chapters already written in the history of development of the North Dome of Kettleman Hills are monotonously identical in the one underlying theme of conservation of oil and gas. Discovered on Oct. 4, 1928, by Milham Exploration Co. with its wildcat Elliot No. 1, the field has been subjected to practically every modern form of produc-tion restraint in the name of conservation. The record thus far developed shows that conservation was had for a time, at a price; and that unitiza-tion must he blessed by single ownership or 100 per cent participation to be effective. In fact, incomplete unitization places a heavy handicap upon its participants in the competitive development that follows.

Jan 1, 1937

By Stewart R. Wallace

"For his achievements in unravelling the complex geology of the Climax ore body; for his leadership in the discovery of the Henderson deposit; for his continued encouragement of young geologists; and for his lecture . .."

Jan 1, 1975

By Charles Fulton

The study of the condensation of zinc from its vapor was undertaken to shed light on certain problems encountered in large-scale electric zinc-furnace work recently conducted. It is a matter of common knowledge that one of the disadvantages of the arc type, electric zinc furnace, is the production of a large amount of blue powder and proportionately little liquid spelter, for, as stated by Stansfield,1 "A notable defect in the electric smelting of zinc ores is the difficulty experienced in obtaining the distilled zinc in the liquid state; when zinc ores are smelted electrically, very little liquid metal is commonly obtained, nearly all of the zinc being in the state of powder."

Jan 8, 1918