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By Spangler Ricker, F. T. Johnson

"SUMMARYThe Ione-Carbondale clays area is 2 miles northwesterly of Ione, Amador County, Calif. It was explored during the war by the Bureau of Mines to obtain data on the alumina content and to recover representative samples for beneficiation tests for alumina recovery.Seventy holes, aggregating 8,837 feet, were drilled, and about 10.3 acres of land was cleared of underbrush. Maps and cross sections were compiled showing location of holes, analyses, and other pertinent data.The clay beds vary in thickness from 13 to 196 feet, and are covered by a loose overburden, averaging about 11.9 feet in thickness. The ratio of overburden to clay is 1 : 8.2. Analysis of a composite sample showed the recoverable alumina (A12O3) and Fe2O3 content to be in the order of 23.6 percent and 2.8 percent, respectively.Topography of the clay area is ideal for open-pit mining methods and plant site.INTRODUCTIONInvestigation of alumina-rich clays for the possible production of aluminum was made during the recent war period, when the shortage of bauxite was becoming critical.Results of field examinations by the Bureau of Mines and the Federal Geological Survey indicated that one of the most promising areas for the development of alumina-rich clays is in the Ione-Carbondale district."

Mar 1, 1948

By George A. Komadina

Pima Mining Company has recently completed their expansion tripling the plant capacity to 18,000 tons per day and now is in the process off expanding to 30,000 tons per day with completion scheduled for the summer of 1967. This paper briefly discusses the additions to the mining department and support areas with a more detailed report on the complete new crushing plant and additions to the concentrator. The crushing plant includes a 54-inch gyratory crusher, three 7-foot standard and seven 7-foot short head crushers along with necessary screens, feeders, and conveyor belts to produce a minus 1/2-inch rod mill feed. The concentrator consists of ten milling sections, each containing one 10-foot by 16-foot rod and two 10.5-foot by 13-foot ball mills, classification is done with cyclones. Pulp from each section is floated in 50 cells of 66-inch Fagergren flotation machines to produce a rougher concentrate which is cleaned in six stages of Denver cleaners to produce a final concentrate The various mill products are thickened with disposal made in conventional manner. Plant instrumentation is discussed in the paper.

Jan 1, 1967

By AIME AIME

M ODERN metallurgy properly belongs to this century. The great advance made in this science is directly attributable to the discovery of the Roentgen rays. Application of the results of this discovery, together with the more recent corroborating studies in electronic diffraction have definitely and for all time established this science. Metallurgists today speak with familiarity of the atoms of the different metals in terms of their orientation, atomic volumes, lattice structures, dimensional lattice constants distance of nearest approach, and the like. One matter of profound interest, which is quite staggering to the imagination of the human mind, is the enormity of the number of atoms even in a small particle of metal. As an illustration, let us compute the number of atoms in the volume of one cubic centimeter in a single grain of absolutely pure copper. Eighteen and a fraction cubic centimeters equal the volume of one cubic inch.

Jan 1, 1940

By S. Banisi, A. Ghasemi, A. Fazeli, M. Rezaei, M. Maleki-Moghaddam

The efficiency of high capacity SAG mills which consume large amounts of energy depends on the grinding and slurry discharge systems. A 9.7 m × 4.8 m SAG mill with radial pulp lifters is used at the Sarcheshmeh copper complex grinding circuit. The process audit indicated that the pulp discharge system was not efficient, judging by the amount of slurry flow back and carry over. These events limited the discharge rate and increased the wear rate of the lifters and grates. With the objective of finding a new design for pulp lifters, a 3D DEM software (KMPCDEM ©), along with the plant operational data and photographic evidence was used. The KMPCDEM © software was used to compare the efficiency of the radial and curved pulp lifter design based on the material flow. The slurry flow was analysed in terms of ease of discharge and lifter wear rate. It was found that changing the radial pulp lifters to curved pulp lifters could improve the discharge efficiency,and decrease wear rate of the pulp lifter in particular at the base of the pulp lifters. The simulation results showed that if curved lifters with a radius of 0.3×mill radius are used, the amount of slurry flow back and carry over will be negligible. It is predicted that by installing the curved pulp lifters, the capacity of the mill increases by 10% and the pulp lifter service life improves by at least 20%. Keywords: SAG mill, radial pulp lifter, DEM,curved pulp lifter, Sarcheshmeh

Jan 1, 2020

By R. G. Meara, O&apos

The land-pebble district of Florida, wnich in 1928 supplied 96.7 per cent of the phosphate production of that State and 82 per cent of the domestic requirements of the United States, is centered in Polk and Hillsboro Counties about 30 miles east of Tampa The deposits are unconsolidated sediments occurring as beds of phosphate matrix overlain by a mantle of barren sands and clays. The matrix consists of a mixture of sand (quartz grains), clay, and phosphate rock in which the coarsest sand is much finer than the coarsest phosphate; that is, the sand is segregated in the fine material. Before the introduction of classifiers the concentration consisted of log washing, and screening at about 20-mesh, which was usually the finest size that could be taken to maintain commercial grade, 66 per cent B. P. L. (bone phosphate of lime) or more. When classifiers were introduced some of the fines that had escaped at the head of the washery and some of the minus 20-mesh material isolated during the washing and formerly lost supplied the feed. During October, 1927, the United States Bureau of Mines in cooperation with the University of Alabama and the Missouri School of Mines and Metallurgy began to investigate the amenability of phosphatic sands to gravity methods of concentration. The work was under the immediate supervision of B. W. Gandrud, acting supervising engineer of the Southern Experiment Station of the U. S. Bureau of Mines at Tuscaloosa, Ala., and Will H. Coghill, supervising engineer of the ore dressing section of the U. S. Bureau of Mines. More comprehensive testing followed and in the early part of 1930 some of the companies cooperated with the bureau and the above-mentioned institutions in conducting a series of tests on hydraulic classification and tabling. The results indicated that marketable concentrates could be obtained with a recovery of 25 to 45 per cent of the phosphate formerly lost. As a result two companies have introduced hydraulic classification to treat the current tailings, and one of them has substituted classifiers for the 20-mesh screens which had been unsatisfactory. Because the phosphate grains and quartz grains have nearly the same specific gravity, the use of concentrating tables by the customary methods is not applicable. The washeries included in the following report are designated as Nos. 1, 2, and 3.

Jan 1, 1931

By David P. Hale

THE Cartersville barite district is near Cartersville, Ga., in the southeastern part of Bartow County, about 43 miles northeast of Atlanta. The area over which active mining is being done extends about six miles in a northeasterly direction and is about three miles wide. Barite production in Georgia began about 1907,1but the existence of the mineral was known much earlier. At present four companies are operating washing plants and three other plants are operating on leases from those companies. The chief impurities in the ores are silica and iron oxide. The silica is easily washed and jigged out and gives little trouble. Any gravity separation between the iron and the barite is generally poor, owing to the slight difference in specific gravity. Two operators have turned to magnetic separation as the solution to the problem and have made remarkable improvements in the finished product. By very close sizing prior to jigging, the separation between iron and barite has been greatly improved. In some localities manganese occasionally appears as an impurity, but is fairly easy to eliminate by gravity methods. A considerable percentage of iron and silica is eliminated by being broken free in crushing. Until methods for the recovery of fine ore were introduced a minimum of crushing was done, but modern methods allow more than formerly. The depression years brought about the need for increased recovery of ore handled on the part of the producers and a demand for a higher grade of product on the part of the buyers. Improvements in milling and mining practice have had a far greater effect, however, than merely the production of a better grade of ore with greater recovery. They have opened for mining large areas that a few years ago were considered noncommercial deposits because of their inaccessibility and their high iron content. It is no exaggeration to say that the new methods have more than doubled present known reserves of barite ore of economic value.

Jan 1, 1938

By Vincent P. Gi. ccnella

GOLD was discovered in Gold Canyon on May 15, 1849. Following this discovery placer miners worked the gravels in the canyon for-ten years, finally discovering the outcrop of the Comstock lode at Gold Hill in May, 1859, and in Ophir ravine on June 12 of the same year. Before long large quantities of gold and silver, were taken from the lode and one of the West's most spectacular mining booms drew thousands of fortune seekers to Nevada. After a long period of production activity waned and in late years little mining was done. The recent reopening of the old mines and the discovery of ore in other parts of the vein, and in other veins of the district, has led to a revival of interest in the Comstock. Virginia City, Gold Hill, and Silver City, situated along the great vein system, are enjoying a period of prosperity and a large influx of people.

Jan 1, 1934

By C DahnTr-Lindqvist

The Kiruna mine produced about 19 Mt processed iron ore in 1999 using sublevel caving. General failure in the hangingwall has been widely studied and its mechanism is rather well understood. Failure in the footwall is more recent and not perfectly explained. Plane shear failure and Hoek and BrayÆs circular failure charts were successfully used to match the first surveyed failure surfaces. The footwall is not free yet but covered by a caved waste rock abutment whose exact behaviour is poorly known. Based on new field data and numerical models (FLAC), the following paper presents recent improvements in understanding the Kiruna mineÆs footwall failure process.

Jan 1, 2000

By Tuomas van der Meer, Jukka Tanninen, Annukka E. Mäkinen, Mika Martikainen, Laura M. Nevatalo

The mining industry consumes huge water volumes and the waste streams typically contain sulfate, which has caused problems to many operations around the world. Discharge of sulfate to fresh waters is being restricted as the sulfate load increases salinity and causes problems when sulfate is reduced to toxic H2S by natural bacteria. To reduce fresh water consumption, internal water recycling had become a necessity in metallurgical processes. However, the recycling causes accumulation of sulfate and other components in water, causing problems to process performance and increases scaling in piping and equipment. Few technically feasible water treatment processes exist in the market that can be applied to decrease sulfate concentration below gypsum saturation level: biological sulfate reduction, membrane separation, ion exchange, evaporation and chemical precipitation. Some of these technologies are effective for treating wastewater, but there is typically a highly concentrated sulfate fraction left requiring still further treatment. Outotec has developed a sulfate removal solution, Outotec Ettringite process, which allows flexible control of residual sulfate concentration, thereby opening doors for increased water recycle within processes and control of the sulfate in discharged waters. In this article the results and benefits of this novel process along with examples of operating costs are presented.

Jan 1, 2014

From some of the largest tunnel projects in the some of the most vibrant cities, to smaller projects in remote corners of the globe, the Robbins Co. announced two tunneling projects in which its tunnel boring machines will be used. Robbins earth pressure balance (EPB) machines undercut Downtown Zhengzhou. Zhengzhou, a city of 7 million people, is set to become a crossroads for rail commerce in China. The country?s future main routes, traveling between Beijing and Guangzhou (North-South), and between Xuzhou and Lanzhou (East-West), will intersect in the city. The plan includes up to four rail lines in Zhengzhou itself, which will eventually link up to the national lines. Excavation of Zhengzhou Metro?s new Line 1 tunnels began on Sept. 28, 2010, when the first of two 6.3-m (20.7-ft) diameter Robbins earth pressure balance (EPB) machines was launched from a 16-m- (52-ft-) deep shaft.

Jan 1, 2010

By C. S. Barrett, O. R. Trautz

PREVIOUS investigations have shown that lithium is body-centered cubic from near its melting point to the temperature of liquid air1,2,3 Nevertheless there was an incentive to search again for a transformation at low temperatures: C. Zener4,5 has remarked that the low value of the elastic modulus (11 - C12)/2 of body-centered cubic metals and alloys implies a rapid increase in free energy with decreasing temperature, which would favor the occurrence of a transformation; also the shear movement to which this modulus applies is one that can transform a body-centered cubic structure into a slightly distorted face-centered cubic structure. It was confirmed that lithium does not transform spontaneously at liquid nitrogen temperature, but it was found that a transformation can be induced at this temperature by cold working the metal,6 and at slightly lower temperatures a different transformation occurs spontaneously. Transformations were also found in solid solutions of magnesium in lithium. THE NATURE OF THE TRANSFORMATIONS Before presenting a detailed treatment of the technique used and the specific data obtained, it would be well to give a brief survey of the general characteristics of the transformations. A new crystal structure begins to form spontaneously in a specimen when it is cooled below a critical temperature. In lithium the structure appears to be close-packed hexagonal; in the Li-Mg alloys most of the diffraction lines (but not all) are near those for hexagonal lithium. The transformation proceeds as the temperature is lowered and soon stops if the temperature is held constant or raised. The course of the transformation on cooling is indicated by the curve at the lower left of Fig I. This curve is drawn in stepped fashion because the transformation goes by discrete steps with audible clicks. Because of the similarity to the decomposition of austenite into martensite in steels, it seems appropriate to designate the beginning of the spontaneous transformation on cooling as the Ms point. On heating to room temperature after the low temperature treatment only the usual BCC structure is found. On heating, the low temperature modification begins to disappear at a temperature which will be designated as Ac. The transformation on heating is halted when the rise in temperature is halted. The temperature must be raised 40 to 50°C above Ac before the reversion is complete-an interval which is sensitive to the rate of heating and to the time of holding at temperatures above Ac. This behavior on heating thus has similarities also to the formation of martensite in the cooling of steels.

Jan 1, 1948

By C. R. Kato, G. Proulx

"Within the continuous scenario of reduced aluminium price and plants production costs increase, the energy consumption optimization in the aluminum electrolytic pots continues as the main focus for the producers. Energy consumption was chosen as a key performance indicator to drive the efforts and actions for improvements. Alcoa improved the energy consumption by approximately 3% from 2005 to 2015. This improvement was a result of best practices implementation, new technologies introduction, strategic actions with plant curtailments and management practices. The main objective of this paper is to highlight the importance of the management practices for planning and operational improvements beyond the technology changes. About 10 years ago, Alcoa reorganized its approach to retain knowledge in the Smelters by using a Best Practices format. For each specific subject, a skilled team defined the minimum requirements and the Best Practices for several aspects of operation and maintenance, which affect the environment, safety, cost, customers and performance. These Best Practices were deployed to all Smelters combined with training sessions to process and operation professionals. We will describe how the Best Practices were organized, the deployment strategy used, and the approach to measure the plants’ success. We will describe the management approach that includes Manufacturing Analyses focused on 3-year potential, annual planning, and weekly monitoring of plant stability. A manufacturing analysis is organized at select plants with cross-functional participation of specialists from technical, operational, procurement and finance. The output of a manufacturing analysis includes a roadmap of enablers to improve energy efficiency. A quarterly follow-up of enabler deployment is held with the plant and resources that participated in the analysis. Annually, there is a Planning Process where energy consumption enablers are selected to be implemented during the next 3 years for each plant. A monthly critical analysis is made by the plants with regional best practice support. On a weekly basis, key performance indicators are reviewed with determination of a stability index for each plant. Any deviation signal of unstable condition is alerted and supporting resources are diverted to the plant to reverse trend with countermeasures.INTRODUCTIONDue to factors like excess aluminum in the market and lower consumption in China, the LME price is declining along the last years, as showed in Figure 1. In 2011, the price peaked at US$ 2,400/ton and since then, continues to trend down and approaching the lowest level at US$ 1,500/ton in the last 5 years."

Jan 1, 2016

By R Symes

The Fosterville Goldmine in Victoria Australia employs the BIOX« Process to liberate gold from its sulfidic flotation concentrate through bacterial oxidation. Gold occurrence is primarily as submicron particles in pyrite and arsenopyrite and has been described as being in æsolid solutionÆ and therefore not amenable to direct cyanidation. Once liberated by the oxidation process, the gold is then available for cyanide leaching. During the oxidation process it has been found that a portion of the liberated gold becomes suspended in the liquid phase in what appears to be a colloidal state. This liquid becomes a waste stream during washing of the oxidised solids and the suspended gold is therefore lost. A method was previously developed using an addition of quebracho tannin to significantly reduce this loss by formation of an iron-tannin precipitate which captures the gold which then reports to the cyanide leach circuit with the oxidised concentrate solids onto which it is adsorbed.This paper discusses the development and plant trial of a second processing step to further enhance gold recovery by use of flotation tailings essentially as a source of extra surface area to capture residual tannin-iron precipitate and its associated gold not recovered in the first step.CITATION:Symes, R, 2012. Recovery of colloidal gold from oxidised concentrate wash liquor - Further improvement, in Proceedings 11th AusIMM Mill OperatorsÆ Conference, pp 383-388 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Oct 29, 2012

By T. M. Girdler

INDUSTRIAL progress and development in this country from the earliest daps to the present has proceeded at an ever-quickening pace. Yet during recent decades the nature of our industrial progress and development has undergone a change of great significance. The earlier days were a period of tremendous expansion. Population was increasing by leaps and bounds. Vast areas of new land were being .2 opened to settlement. And almost boundless new sources of timber, coal, oil, ores, and power were being opened to ever-expanding markets. Today, however, that picture has al- most completely changed. Today, with population increase tapered way off and the opportunity for free expansion into western frontiers gone, the great industrial development of our country continues on a vastly different front. Industrial progress and development today rest on a foundation of technology. The key- stone is research. Our frontiers to- day are frontiers of sciencec

Jan 1, 1939

By G. H. Hope, A. R. Maycock

"La Mine Doyon is a gold mining operation located in northwestern Quebec, approximately 35 km east of Rouyn-Noranda and 85 km west of Val d'Or. The mine is jointly owned by Lac Minerals Ltd. and Cambior Inc. with Lac Minerals as the manager. Production statistics as of February 1987 are 6.4 million tonnes milled at an average grade of5.8 g/t Au. Current reserves of9.9 million tonnes at 5. 7 g/ t Au to a depth of400m have been outlined. Indicated reserves below this horizon could considerably increase this reserve.The mine currently consists of two open pit and two underground mine operations, producing approximately 3600 tonnes per day of ore at an average grade of6 g/t. The ore is currently processed at the La Mine Doyon mill at a rate of1400tid and at Lac's East Malartic mill at 1950 t/d. Ore is also processed intermittently at Lac's Les Terrains Auriferes mill and at Noranda's Horne Division.La Mine Doyon is currently in the midst of a program to expand and upgrade the mill at La Mine Doyon. The expansion to 3000 t/day includes the conversion of the existing crushing and grinding circuits to a SAG (semi-autogenous grinding) mill circuit and the existing filter wash plant to a CIP (carbon-in-pulp) recovery plant. The economics of this project are based on reduced operating costs (milling and trucking) and improved recovery due to updated technology. HistoryThe area between Noranda and Val d'Or has a long history of mining activity in both base metals and gold, dating back to the early 1930s. More recently, several new orebodies have been discovered and exploited in the area including La Mine Doyon, Lac's Mine de Bousquet, Dumagami, and the Kiena operation.La Mine Doyon was discovered in the early 1970s, and brought into limited production in late 1979. The mine was started on are reserves of 2.75 million tonnes at 6.2 g/t and was, thus, considered a small, short-term operation. Mining started at an initial rate of 550 tI d with all the ore being shipped to Noranda's Horne smelter as flux. When Lac's East Malartic mill became available for custom milling, Doyon commenced shipping to that facility at a rate of 650 t/d. As a result of some equipment additions and an improved understanding of the ore, the East Malartic mill throughput was gradually increased from 650 t/d to the current rate of 1950 t/d."

Jan 1, 1988

Ninetecn papers and a round table. as follows: The Future of the American Iron and Steel Industry (Howe memorial Lecture), by Zay Jeffries; Rote of Carbon Elimination and Degree of Oxidation of metal Hath in Isasic Open-hearth Practice. 11, by ,Alexander L. Feild; A New Method for determining lron Oxide in Liquid Steel, by C. H. Herty. Jr., J. M. Gaines. Jr., H. Freeman and M. W. Lightner; I'racticsl Obarrvntions on Manufacture of basic Open-hearth, High-carbon Killed Steel, by W. J. Itcagan; Production of Gray lron from steel Scrap in the Electric Furnace, by T. F. Baily; reclaim ing Steel-foundry Sanda, by A. H. Dierker; Influence of Rate of Cooling on Dendritic Structure and Microstructure of Some Hypocutectoid Steel, by Albert Sauveur and C. H. Chou; Transformation of Austcnite at Constant Subcritiral Temprratures, by I?. S. Dnvenport and E. C. Bain; Progress Notes on the Iron-silicon Equilibrium Diagram, by Bradley stoughton and S. Greiner; Influence of Nitrogen on Special Steels and Some Experiments on Case-hardening with Nitrogen; by Shun-ichi Satoh; Production and Some properties of Large Iron Crystals, by N. A. Ziegler: Tensile Properties of Rail and Other Steels at Elevated Temperatures, by John R. Freeman, Jr. and G. Willard Quick; Endurance Properties of Steel in Steam, by T. S. Fullcr; Development of Casing for Deep Wells; a Study of Structural Alloy Steels, by F. W. Bremmer; Electrolytic Iron from Sulfide Ores. by Robert D. Pike, George H. West, L. V. Steek, Ross Cummings and B. P. Littlc; Sintering Limonitic Iron Ores at Ironton, Minnesota, by Perry G. Harrison; Concentration of the mesabi Ilematites, by E. W. Davia; Resistance of Iron Ores to Decrepitation and Mechanical Work, by T. L. Joseph and E. P. Barrett; Experiments Demonstrate Method of Producing Artificial Manganese Ore, by T. L. Joseph, E. P. Barrett and C. E. Wood; Iron Ore Round Table.

Jan 1, 1930

By C Delwig

ThyssenKrupp specialises in the manufacture of high-grade steel-sheet products. Its main customers include the automotive, construction, household appliance, energy and packaging industries.At its works in Duisburg, Germany, ThyssenKrupp Steel Europe produces 12 Mt of crude steel annually, making Duisburg one of the world’s largest steel hubs.ThyssenKrupp have installed an online elemental analyser and limestone dosing control System on one of three Sinter strands at Duisburg in an attempt to control the sinter raw mix with better precision. Traditionally, set point changes to the raw mixture were made after sampling and laboratory analysis of the sinter product. The analyser chosen uses prompt gamma neutron activation analysis to determine the elemental content of moving material on a conveyor each minute and was supplied by Thermo Fisher Scientific. The project goal was to control the CaO/SiO2 ratio (basicity) and reduce its variability in the sinter feed.Evaluation of the system has shown that the addition of the online analyser reduces the time lag related to the former method, therefore upset conditions can be reacted more quickly by the control system, and this has resulted in a more stable sintering process. As a result, the sinter feed variability in case of the basicity has been reduced by half. While CaO/SiO2 control was the initial aim of the project, a number of other benefi ts have been realised, such as a reduction in return fi nes and a financial benefi t of 0.11 €/ton of sinter attributed to the reduction of coke breeze and limestone. ThyssenKrupp Steel Europe has identifi ed that additional information available from the analyser could be used to optimise the complete sinter process.The project was carried out with a financial grant of the research program of the ‘Research Fund for Coal and Steel’.

Jul 11, 2011

By Roshan B. Bhappu

Although the economic importance of recovering copper by leaching of mine work dumps from open-pit operations has been realized for some time, serious attempts to understand and to improve such operations through scientific research has been made only in recent years. This progress report covers the results of chemical, physical, and biological studies pertaining to the dump leaching process and discusses salient features and parameters that may be helpful in improving such operations.

Jan 1, 1968

By Sami Kara, Yunseok Park, Seung-Joong Lee, Namsun Hwang, Michael Laing

This study conducts a comparative analysis of construction efficiency. In the first part we compared electronic and non-electric initiation systems, focusing on tunnel contour holes. Field blasting operations were executed across a variety of delays to identify the optimal delay time. This delay for the in-situ rock mass was determined through regression analysis of blasting vibration in contour holes and for overbreak/underbreak. The blasting results with the electronic initiation system using the obtained optimal delay, applied to contour holes, were compared with the results of the non-electric initiation system. The overbreak and underbreak decreased by an average of 2.7 cm and 5.8 cm respectively, by using the electronic initiation system. Moreover, the vibration reduction rate in contour holes region was reduced by 11.9% based on the blasting vibration estimation equation proposed by the Ministry of Land, Infrastructure, and Transport (MOLIT). Underground construction projects have become increasing popular as cities grow in both size and density. This growth severely limits the amount of useable space for new project on the surface, resulting in the decision to build them underground. This new policy however brings into focus the challenge of managing and reducing blasting related vibration due to the proximity of these projects to sensitive structures, utilities and foundations often present in urban environments. For this purpose, we have been required to manage the vibration by reducing the quantity of explosives used per round. Inspired by surface blasting techniques, we applied a decking mode to address and work around this challenge. We present in this paper the first attempt to blast a tunnel face using a decking method and reduce the charging per hole from 6 kg to 3 kg per hole and keep the same advance rate for this tunnel. The results are presented in the third part of this paper. In the second part we present the results of the decking mode in shaft. The use of the electronic initiation system in tunnel construction provides the users an effective tool to improve the overbreak/underbreak and keep the vibration at a low level with a large gain on the overall project schedule and budget. This what we want to demonstrate in this paper.

Jan 21, 2025

By Richard L. Ashbrook, John F. Wallace

Several high-temperature eutectics of cobalt and nickel alloys were modified by small additions of selected elements. Thes-e alloys were compared to unmodified melts for microstructural variations. A few modified compositions were selected on the basis of structure and their tensile and stress-rupture behavior determined. The results of stress-rupture tests in air at 1800 F and room-temperature tensile tests of four high-temperature eutectics showed modification capable of producing substantial improvements in properties. The microstructures were altered and mechanical properties improved by: a.) dispersing a subordinate phase more uniformly throughout the matrix; b) replacing large continuous -network or platelike constituents with small equiaxed discontinuous phases; and c) by forming new, finely divided phases. tHE term "modification" is most commonly used to describe the refinement in microstructure of the Al-Si eutectic that occurs as a result of rapid cooling from the melt or on slow cooling after treatment with small amounts of sodium.1 "Modification" has also been used to describe the change from flake to spheroidal graphite in the austenite-graphite eutectic of cast iron.2 This change of graphite shape is accomplished by small additions of cerium or magnesium.3 Other systems have also been shown to be capable of modification, for example: Pb-Sn by copper;4 Al-Cu by sodium;5 Al-Mn by sodium;5 and Pb-Sb by aluminum.5 Although modification of Al-Si alloys and cast irons is usually accompanied by improved mechanical properties, a general definition of modification has been suggested to include the effect of small quantities of impurity elements on the microstructures of all eutectic alloys, regardless of the effect on the mechanical properties.6 In this paper, the term "modification" is employed in a broad sense to include the formation of third phases or even the supplanting of one of the binary eutectic phases by a third phase. The mechanism of modification, as for any solidification phenomenon, must be considered primarily in terms of nucleation and growth. Although both nuclea-tion and growth mechanisms are required to explain all the phenomena observed in connection with the solidification of modified eutectics, various investigators have usually favored one or the other.7"16 It has been shown that modification of a binary eutectic can be effected by addition of a solute element that has greatly different distribution coefficients or k values in the two phases of the eutectic. Under these conditions, differences in the temperatures at the solid-liquid interfaces of the two phases retard the growth of one phase with respect to the other.4 It has also been shown that increased undercooling favors a transition from a rodlike eutectic to a globular eutectic.17 A mechanism proposed for the transition from lamellar to rodlike eutectics depends on the concept of constitutional super cooling.18 The modification of eutectic alloys may be of interest for high-temperature service as well as at room temperature. Although "high-temperature eutectic alloys" may appear to be a contradiction in terms, many eutectic systems, including those studied in this work, have melting points in excess of 2400°F. One of the mechanisms by which high-temperature alloys are strengthened is dispersion of a relatively brittle phase such as an oxide, carbide, or an inter-metallic compound throughout a ductile matrix. For a given volume fraction of dispersed phase, strength is increased by decreasing the size and spacing of the dispersed particles.19'20 Furthermore, room-temperature ductility may also be increased by changing the shape of a brittle dispersed phase from platelike to equiaxed or spheroidal.8 Overaging and redissolving of the secondary phase limit the maximum temperature to which precipitation-hardened alloys can be used. However, in a binary eutectic system, both phases coexist up to the melting point. Although all eutectic structures are not completely stable,21 a dispersion-hardened cast high-temperature alloy might result if a fine distribution of one of the eutectic phases could be obtained during solidification. An additional reason for interest in eutectic alloys is their excellent castability.22 Since eutectic alloys, like pure metals, freeze at a single temperature rather than over a range of temperatures, their castability is superior to solid-solution alloys with long liquidus to solidus ranges. The purpose of this research was to study the effects of small solute additions on the microstructure and mechanical properties of a number of high-melting-point eutectic compositions.

Jan 1, 1967