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By Gaither H. Kitchell

Introduction Fire assaying is an ancient method of determining the amount of gold and silver in geological materials. Today's commercial, mining, school, and private fire assaying laboratories still use this basic assaying method. One of the primary reagents used to collect gold and silver from the ore is litharge (PbO), or lead oxide. The Federal Occupational Safety and Health Administration's (OSHA) and the Nevada Division of Occupational Safety and Health's (OSH) have a lead standard. It states that a person exposed to airborne lead at concentrations greater than 50 µg/m3 (1.4 µg per cu ft) of air over an eight-hour period has gone beyond the permissible limit for health safety. It is not uncommon to get airborne lead concentrations of 1400 µg/m3 (40 µg per cu ft) in the flux/sampling area or 900 µg/m3 (25 µg per cu ft) around the gas/ electric furnaces during the fusion and cupelling phases. Therefore, any individual working in these areas for more than 30 days per year without proper protection is a likely candidate for lead poisoning. Lead In A Human Lead enters the body as a toxic substance by breathing it into the lungs and upper respiratory tract and by getting lead particles into the digestive system through ingestion. Smoking, eating, drinking, chewing tobacco and gum, or wiping a lead-contaminated hand across the mouth are all potential ways forgetting lead into the body. Lead taken in large quantities can actually kill a person in a matter of days. This is rare, however. The real hazard of lead overexposure is for the unsuspecting person who works in an unsafe lead environment for months or years. This individual can slowly receive damage, sometimes permanent, to the central nervous system, gastrointestinal tract, kidneys, blood, gums, and reproductive system. Safe Blood-Lead Level The Lead Standard states that the maximum safe blood-lead level is 40 µg/100 g (40 µg per 3.5 oz) of whole blood. It recommends 30 µg/100 g (30 µg per 3.5 oz) if a person is of child-bearing age. People not working around lead products normally have a blood level of less than 10 µg/100 g (10 µg per 3.5 oz). A person not adequately protected can exceed 40 µg/100 g (40 µg per 3.5 oz) in a few weeks by fire assaying only 100 samples per day per week. Studies show that some individuals have developed lead-related diseases with blood-lead levels less than 80 µg/m3 (2.3 µg per cu ft). Lead Poisoning Symptoms There is a long list of symptoms associated with lead poisoning. The most common are: a prolonged, sweet, metallic taste in the mouth; loss of appetite; anxiety and irritability; weakness and dizziness; nausea and tremors; and insomnia. Preventive Measures Based on the lead standard, a number of preventive measures can be taken to ensure that fire assay laboratory personnel frequently exposed to lead are protected against overexposure. First, the actual lead concentration within the assaying area should be determined. In Nevada, one can contact the Department of Industrial Relations, Division of Occupational Safety and Health for assistance in monitoring any laboratory. The agency will also recommend ways to protect against lead. This agency does the monitoring and provides an educational class on lead safety. This type of agency can be found in other states. Commercial consulting firms are also available, but they are expensive. Regardless of the technique used to determine lead concentrations, it is most likely that the average fire assay area exceeds the 50 µg/m3 (1.4 µg per cu ft) lead concentration limit. This is considered unsafe.

Jan 8, 1985

By William Gleason

"It is safe to say that the coal industry, in the United States and globally, is currently suffering through one of the hardest times in its history.A perfect storm of competition, changing energy demands, politics and public perceptions have collided, inflicting significant harm to the industry that many say is irreparable. This, in turn, has led to massive job losses in some regions, heavy cuts in production and even bankruptcy filings from two of the largest coal mining companies in the nation.Cheaper natural gas can certainly take a large share of the blame for the struggle of coal, as utility companies switch from coal to natural gas for power generation. According to the U.S. Energy Information Administration (EIA) the amount of coal used for electricity generation in the United States is at a 45-year low.November 2015 marked the fifth consecutive month that natural gas was the leading source of power generation in the United States. EIA said generators produced 101,866 thousand megawatt hours (MWh) of electricity with gas in November versus just 87,789 thousand MWh with coal, the lowest monthly level since May 1980 when monthly coal use was 84,884 thousand MWh.According to Robert Godby, director of the Center for Energy Economics and Public Policy at the University of Wyoming, there are a number of factors playing a role in the decline of coal, but he points to the advances in fracking as the tipping point.“A lot of people will argue that regulation is the cause of the decline, and it has played a part, for sure, but the story of the recent past is more about what competition has done to the energy market,” Godby told Mining Engineering. “The war on coal was originally declared by natural gas in 2008.”The price of natural gas, which was at $13 per million Btu before the gas fracking boom, has fallen to as low as $1.68 in December 2015. Likewise, Godby said the cost of wind generation is now lower than the cost of generation from coal and the cost of solar generation is coming down as well. In addition to that, the demand for energy has changed in the past five years with more efficiencies in everything from building design to lightbulbs."

Jan 1, 2015

By Thomas T. Read

EVERYONE engaged in the teaching of mining engineering will, I suppose, agree that the most difficult subject to teach is "Mining Methods." One primary difficulty is that the students taking the course have either had no previous experience in mining, or else they have had; either seeming to be somewhat of a drawback. The students who are unfamiliar with mines find it difficult to visualize underground conditions, as described and illustrated with sketches and maps, while those who have had underground experience seem to 'find it difficult to visualize anything much different from that which they have already seen. This reminds one of the remark about the Presbyterian doctrine of predestination, to the effect that "you are damned ,if you do; and damned if you don't."

Jan 1, 1930

By Md. Amanullah

A novel triple action load cell assembly (LCA) was developed to determine three index parameters reflecting compressive, tensile and shear characteristics of mudcakes. The results indicate that the tensile, compressive and torsional behaviour of mudcakes are strongly influenced by the physics and chemistry of the mud additives. Eine neuartige dreifach wirkende Druckkammer zur Bestimmung der drei Indexparameter Druck, Zug, und Scherung von Spülungskuchen wurde entwickelt. Die Ergebnisse weisen auf einen starken Einfluss der physikalischen und chemischen Spülungszusätze auf Druck, Zug, Scherung hin. Un assemblage d'une nouvelle cellule a triple action (LCA) a été développée pour déterminer trois paramètres caractérisant la compression, la contrainte en traction et la résistance á la fracture des cakes. Les résultats indiquent que les comportements tensile, compressif et de torsion des argiles sont fortement influencés par la chimie et la physique des additifs des boues.

Jan 1, 2003

By S. Floreen

Seven iron alloys ranging from 5 to 12 pct Ni and 5 to 14 pct Cr were studied. All alloys transformed to bcc massive martensites. Tempering increased the strengths , probably because of relief of residual stresses generated by the martensite transformation. The major strengthening mechanism appeared to be solid-solution hardening by nickel and chromium. Studies of the work-hardening behaviw, of the effects of prior austenite grain size, and of the effects of changing strain rate and test temperature gaue results very similar to iron or low-alloy steels. Increasing nickel contents markedly improved the toughness at subzero temperatures. Studies of the flow properties did not, however, indicate the reason for the beneficial effect of nickel on toughness. The marine atmosphere corrosion resistance of the alloys was improved primarily by chromium additions, but increasing nickel contents were also beneficial at low levels of chromium. J\ number of maraging and PH stainless steels are strengthened by precipitation hardening in a low-carbon Fe-Ni-Cr martensite matrix. To some extent the resultant properties of these steels must depend upon the properties of this matrix. The present study therefore was conducted to evaluate the transformation characteristics and mechanical properties of a series of Fe-Ni-Cr martensitic ternary alloys. A limited evaluation of the corrosion resistance of the alloys in marine atmosphere was also made. ALLOY PREPARATION Seven 100-lb air induction melts were prepared using electrolytic iron, nickel, and chromium metal additions. The initial Fe-Ni charge also contained 0.05 wt pct graphite to produce a carbon boil during melt down. After melting of the base charge, the heats were refined with 0.1 wt pct additions of manganese, silicon, aluminum and titanium and poured into cast-iron molds. The ingots were homogenized at 1250°C and uni-directionally hot-rolled to 2-in. plate. They were then homogenized another hour at 1250°C, and unidirection-ally hot-rolled to %-in. plate at a finishing temperature of approximately 1050°C. The compositions of the heats are given in Table I. Two additional heats were prepared as 40-lb vacuum-induction melts using electrolytic iron, nickel, and chromium metals, and commercially pure molybdenum chips. A carbon boil, and 0.1 wt pct additions of aluminum and titanium were again employed, but manganese and silicon were not added. The heats were converted to %-in. plate using the procedure described above. The compositions of these heats are included in Table I.

Jan 1, 1967

By B. Cousins

Flotation reagents are critical to the optimum performance of flotation circuits. How a flotation reagent performs within the first few cells of a flotation train is a key indicator of how well it will perform throughout the entire circuit. A method to compare reagent performance was recently developed by Ashland Water Technologies. The procedure involves collecting a timed sample of concentrate from each cell and then measuring the volume of the settled solids. An estimate of the percentage of concentrate collected from each cell can then be mathematically determined, providing an understanding of the recovery changes in each cell. Data from trials at a coal flotation circuit are used to demonstrate the method's validity.

Feb 27, 2013

By R. L. Virta

Common clay is a natural, fine-grained material composed of hydrous aluminum silicates. Shale is a laminated sedimentary rock that is formed by the consolidation of clay, mud or silt. Production About 160 companies produced common clay and shale in 41 states. In states not reporting production, common clay and shale probably was mined and sold for construction applications by companies not participating in the U.S. Geological Survey’s canvass of producers.

Jan 1, 2005

Mineral Processing Education in China

Sep 13, 2010

By Mary Ellen Bruce

Let me first address the issue of the wet grab samples. The wet grab samples that were attempted to take on the Central Artery were hindered by the fact that the way the mixing was being done was only by injecting grout on the way out, during withdrawal of the mixing tools. They would auger down to the required depth (usually with some water being injected), which took anywhere from 45 minutes to an hour, and then when coming out, the grout would be injected with grout. That was leaving a column of grout in the center where the shaft had been (i.e. inside of the blades of the mixing tools), which would end up being something like a foot in diameter because the pipe that was used for the drill shaft was a foot in diameter. So we had 10 inches to a foot of almost pure grout in the middle of our column and then we had 2 feet on either side that was mixed soil cement. So when they went down with the wet grab sampler not knowing where that was in the column sometimes they/we were getting strengths of 1500 psi, and sometimes they/we were getting strength of 500 psi or 100 psi. So what was it that we were taking into the wet grab sampler? In those cases you don't really know, but it wasn't representative of the core samples we were taking. We were purposely not coring in the center because we knew that was going to be high cement content, almost pure grout. So the issue of wet grab sampling particularly on this project, the Central Artery Project, was that we didn't really know what we were sampling. What becomes an issue with wet grab sampling in other projects is that you have to have another device (machine) in most cases, a cherry picker crane or something similar that can raise and lower with a beam that is used to forces the sampler down into the freshly mixed soil-cement. And regarding economics, is it more economical to have that crane standing by with its operator or to have a drill rig to come along later and do the coring and take the material out that's fairly identical to what you're finding in situ? The complaint of micro-fracturing in the core samples as you're taking the cores was raised by Seiko as causing large strength reductions. But, if you're doing it carefully, then I don't think that's much of an issue anymore, on research basis perhaps but not on a practical level.

Feb 10, 2003

The prime objective of geometallurgy is to improve the profitability of mines through the use of spatial models of rock properties that have a significant impact on value. Although a key property is the grade of the component of interest, because it directly influences the revenue from saleable material, increasingly attention is being focused on other attributes. These 'non-grade' variables may have a less direct, but equally profound impact on value, either by reducing potential revenue (eg lowering recovery, deleterious elements, etc) or increasing mining or treatment costs (eg comminution, grindability, throughput, reagent use, etc). Collectively, these variables have been described as 'geometallurgical'. There are three main areas of activity required to realise the value of geometallurgy: 1. acquisition of appropriate data through sampling and measurement, 2. building spatial models of geometallurgical variables, and 3. using these models to optimise value. Each of these is built on the foundation of the preceding step. In building reliable spatial models, it is critical that the amount of error introduced to data by the sampling and measurement processes is understood and quantified, in order that the inherent variability of the component of interest can also be properly understood. Management of the quality of grade variables is now applied (with different levels of diligence and success) across nearly all sectors of the mining industry, not least because of the necessity to adhere to Codes of practice (eg JORC, 2004). The necessity for quality management and at least the broad framework of what to do in practice is reasonably understood by many relevant professionals. There are also a number of tools, including software products, statistical analyses and presentation formats, available for those managing grade data. It is also abundantly clear, that in many cases people have little understanding of why they are doing particular quality control activities, or how to sensibly interpret the results. The same is not true for many geometallurgical variables. In almost all instances the authors have seen, the magnitude of sampling and analytical/measurement error variance embedded in geometallurgical test data is untested and unknown. This is partly because until relatively recently, metallurgical data has mainly been collected for the purpose of process and mill design, with few, expensive tests carried out on 'average' samples of the orebody. Increasingly however, there is a move towards collection of much larger data sets from spatially distributed sampling, and thus a growing necessity to understand the errors inherent in both sampling and analysis of these types of variables, and how to manage them. In order to understand how the quality management practices applied to grade variables can be extended to geometallurgical variables, it is essential to understand the theoretical foundation that supports these practices. This requires an analysis of the concepts that underpin the 'principles of additivity' (Matheron, 1963), the 'theory of sampling' (Gy, 1982, Pitard, 1993), and 'statistical process control' (Shewhart, 1930). Relevant concepts are then integrated to form a foundation to develop methods to improve the quality management of geometallurgical variables. Application of this framework will significantly increase the integrity of geometallurgical data, the reliability of geometallurgical models and ultimately the value derived from implementing geometallurgy. This is an ABSTRACT ONLY no paper was prepared for this presentation.

Mar 1, 2010

By J. Kemeny, R. Fuentealba, C. Rodriguez, F. Fernandez, M. Rocha, T. BoBo

"Mathematical modeling in conjunction with mineral characterization is widely used as a method for design and optimization of comminution circuits, to simulate the processes of crushing, grinding and classification. An important input parameter to the simulation models is the Run-of-Mine Particle Size Distribution (ROM PSD). The run-of-mine size distributions due to blasting have a great influence on the performance of a semi-autogenous grinding (SAG) mill. In this paper, a mine case study was conducted where there are four primary geologic units and the material properties between the four units vary considerably. Also, the mixture of the four unit that will be mined at any given time also vary considerably. This presents a challenge in terms of optimizing the blasting for mill production throughout the mine life. As part of the case study, field rock mass characterization, laboratory rock mechanics tests, and laboratory breakage tests were conducted. The field characterization and rock mechanics tests provide material properties used to simulate the effect of different blast designs on run of mine particle size distributions (ROM PSD). The JKSimBlast software was used for these simulations. The rock breakage tests provide material properties used to simulate crushing and grinding performance. The JKSimMet software was used for these simulations. The goal of the mine is a mill throughput of 95,000 tonnes (104,720 tons) per day (TPD). Based on this goal, run-of-mine fragmentation analysis was conducted for four blasting designs resulting in powder factors of 0.44, 0.54, 0.64, and 0.94 kg/t. The powder factor of 0.44 represents a standard blasting design, while the 0.54 and 0.64 kg/t designs are high-energy blasts specifically to assist with mill production. The 0.94 kg/t design was investigated for the one geologic unit with very high strength. The results of the run-of-mine fragmentation analysis was then input into a crushing and grinding simulation model to predict the mill throughput for the time periods of 1-5 years and 6-10 years. The results indicate that certain blast designs are able to achieve the 95,000 tonnes TPD (104,720 tons TPD) goal, while other blast designs were not. A standard blast design with a 0.44 kg/t powder factor, for example, was not able to achieve the throughput goal, while a design with a 0.64 kg/t powder factor was able to achieve the goal in both the 1-5 and 5-10 year time periods. INTRODUCTION In recent years, mathematical modeling in conjunction with mineral characterization has been widely used as a method for the design and optimization of comminution circuits. The Run-of-Mine Particle Size Distribution (ROM PSD) is a function of rock properties and design parameters of the blast and has a significant impact on the crushing and grinding treatment circuit. Traditionally, design of the grinding treatment is estimated using only the F80 value instead of the full distribution of sizes in the feed, but the finer sizes have great influence on the treatment of a grinder, particularly in the SAG mill."

Jan 1, 2015

By Robert F. Randolph

Real-world levels of attenuation from hearing protection devices are usually much lower than the rated values obtained under near-ideal circumstances. The shortfall is even more extreme for earplugs than it is for earmuffs, primarily because of the complicated process of fitting the plugs within the ear canal. This study examines the use of a commercially-available lubricant for hearing aids to determine whether it would facilitate improved fit and attenuation for earplugs. In this experiment, ten participants inserted earplugs with and without using the lubricant. Average attenuation was assessed with the Real-Ear-Attenuation-at-Threshold (REAT) technique, and showed over 5 dB improvement when the lubricant was used. Participants obtained an 85% mastery rate using the lubricant versus a 50% mastery rate without. These results indicate several possible applications for improved earplug performance in real-world settings where hazardous noise is unavoidable and effective hearing protection is necessary.

Jan 1, 2008

By W. Chae

The influence of solution ionic strength (IS) and electrolyte valence on the flotation behavior of malachite has been investigated. The microflotation tests were conducted over a range of solution IS (1?300 mM) at a constant speed (340 rpm), pH (9.5), flotation time (10 min), and sodium oleate dosage (5.3×10-7 moles/g). The size of malachite ranged from 45 to 53 µm, and two different types of electrolytes (NaCl and CaCl2) were employed. Electrophoretic mobility was also measured over the same IS range employed in the microflotation study. Overall, strong coupled effect of solution IS and ion valence was observed. Specifically, the flotability of malachite increased with increasing IS in the presence of monovalent cation (Na+) while the flotability increased up to 30 mM and decreased with increasing IS in the presence of divalent cation (Ca2+). Notably, the flotability of malachite was greater with the presence of Na+ compared with Ca2+ under high IS conditions (IS>30 mM). Consistent trend for Na+ versus Ca2+ was observed from the flotation results with different SO dosages. The characterization and flotation results suggested that the trend was likely attributed to the increased unfavorable interaction between malachite and bubble via the charge reversal of bubbles and malachite at higher IS in the presence of Ca2+.

Feb 27, 2013

By Mark Abernathy

When most people think of a motor vehicle accident, the direct costs resulting from that accident, such as vehicle repair or towing charges, are generally easy to quantify. However, the indirect costs associated with an accident are often overlooked. These indirect costs can take a tremendous toll on a company in more ways than you might think.

Jan 1, 2006

The London Metal Exchange began its first official session of aluminum trading on Monday, October 2, LME prices based on 3-month forward contracts opened Monday at 52.4 cents per pound, fell midway through the week to 52.3 cents and ended Friday at a high of 52.7 cents. For the week, LME metal averaged 52.5 cents. Although Reynolds Metals Co. and Aluminum Co. of American continued in September to value unalloyed 99.5 percent aluminum ingot at 53 cents per pound, other producers were at higher positions of 55-57 cents. Alcan Aluminum Corp. of Alcan Aluminum, Ltd., a Canadian producer, increased prices for its U.S.-marketed ingot by 2 cents to 55 cents per pound, effective September 21. New York merchants increased ingot quotes by approximately 0.5 cents to 52.8-53.5 cents per pound.

Jan 1, 1978

By Martin Bouchard, Bruno Paillard, Jean-Claude Dubé, André L’Espérance

"A precise analysis of the noise emitted by an aluminum plant has shown that one of the main sources of noise is the noise emitted by an exhaust stack 40 m high and 1.8 m diametre, emitting a pure tone at 320 Hz. Because a classical cost effective solution is not available for this source, active noise control (ANC) solution was investigated.Commonly available ANC systems, how-ever, are not applicable to the chimney considered because the diameter of the stack (f) is too important compared to the wave length(?)of the frequency to control. In fact, until now, active noise control (ANC) has been successfully used to reduce the acoustical energy emitted at the end of ducts in the case of plane wave propagation, i.e. ?/f< 1.7 [1,4].When f> ?/1.7, high order modes propagate in the duct and a single canal active noise control system is not sufficient.This paper presents an ANC system developed to control higher modes in a circular duct. The controller used is based on a multiple-input, multiple-output adaptive filtered X-LMS and allows up to 11 error micro-phones and controls sources. The system has been used in a laboratory on a finite duct of3.5 m long and 0.30 m diameter which corresponds to the same ratio ?/f for the real stack. The efficiency of the system with different numbers and location of control sources and errors sensors has been analyzed. Noise reduction of 15 dB(A) could be obtained with some configurations. Actually, the system is being considered for installation on the real chimney stack."

Jan 1, 1997

On behalf of the Council and staff of The South African Institute of Mining and Metallurgy, it is my privilege to wish all members and subscribers a very Happy Christmas and a Prosperous New Year.

Jan 1, 1988

By D. A. Thomas, E. S. Meieran

Tungsten wires were examined by transmission electron microscopy after drawing and after high-temperature annealing. Drawn wire consists of highly elongated grains called fibers, whose long axis is parallel to [110]. Each fiber is ribbon-shaped, with the wide dimension of the ribbon parallel to (001) and the narrow dimension parallel to (110). Furthermore, most fibers are bent about [I10] and twisted along their length. The fibers are divided into cells, which in some cases contain a platelet substructure lying on (110) planes. The misorien-tations of these platelets accumulate to allow the macroscopic twist of the fibers. During annealing, several competing reactions occur, starting at different temperatures and progressing at different rates. Among these processes are fiber-boz~ndary migration, polygonization, dislocation rearrangement, and possibly impurity segregation. The fiber-boundary migration accompanied by the formation of transverse boundaries during polygonization leads to an equiaxed grain structure although recrystal-lization does not occur. There is a relationship between the flow stress of the wires and their average subgrain width in the form sy = s0 + kyd-1/2 . Also, there appears to be a relatio&apos;nship between wire ductility and the formation of transverse boundaries during annealing at about 800°C. THERE have been many investigations of the structures and properties of tungsten wires1-4 due to their commercial importance for use as lamp filaments. The structural studies have so far been limited to optical microscope and replica electron-microscope studies. due to the difficulty of .-me- paring from wires thin foils which can be examined by transmission electron microscopy. However, this difficulty has been recently overcome,5 and it is now possible to examine tungsten wires by transmission electron microscopy as well as by other techniques. In this paper, the structure of drawn tungsten wire is described, as are the changes in the structure during high-temperature annealing. Some discussion of the relationship between structures and properties is also given. EXPERIMENTAL MATERIALS AND PROCEDURES Commercial 0.030-in.-diam doped tungsten wires drawn at progressively decreasing temperatures between about 1400° and about 800°C were examined. The composition, mechanical properties, and optical microstructures are described in detail elsewhere.&apos; All experimental materials were vacuum-annealed for 10 ot 30 min at temperatures at 100°C intervals between 700° and 2000°C. Specimens were thinned for examination in the Siemens Elmiskop I electron microscope by the method of Meieran and Thomas.5 STRUCTURE OF AS-DRAWN WIRE The optical microstructure of as-drawn tungsten wire has been described by Peck and Thomas.7 They observed that wire in longitudinal section consists of highly elongated grains called fibers whose width varies between 1 and 10 µ, while in transverse section the fibers appear to be elliptical in cross section and bent about their common [110] wire axis. They explained this unusual appearance as being due to the drawing of a bcc material with a [110] texture, and predicted that the wide and narrow planes of the fiber cross section would be parallel to (001) and (110), respectively. The fibers apparently bend about the [110] axis during drawing to maintain grain boundary continuity during drawing. Transmission electron microscopy offers a way of checking these predictions as well as providing a more detailed picture of the wire structure. Figs. 1, 2, and 3 are typical electron micrographs of

Jan 1, 1965

By W. T. Wertman

LABORATORY research has been started at the Bureau of Mines Morgantown Petroleum Research Laboratory, Morgantown, Va., to investigate the possibilities thermal-recovery methods for producing crude oils of high API gravity found in oil reservoirs of the eastern United States. This bibliography on thermal methods of oil recovery was compiled as a part of the work. Crude oil discoveries to December 31, 1958, in the United States were estimated to exceed 270 billion barrels. Cumulative production of crude oil through 19.55 was about 60 billion barrels, and the American Petroleum Institute estimates that an additional 30.5 billion barrels are economically recoverable by present methods. On this basis, about two-thirds of the oil that has already been found can be classified as economically unrecoverable for lack of a satisfactory method. The rap icily rising costs of proving new deposit; of domestic petroleum, the lack of new discoveries of large oilfields in the united States, and I he growing demand for crude oil have caused an acceleration of research to develop new or improved methods fur producing "unrecoverable" oil in known reservoirs.

Jan 1, 1960

By J. B. Clark, A. S. Yue

The zone-melting technique can be adapted for the de-termination of the eutectic composition in complex metal systerrzs. The application of this method is demonstrated in a simple eutectic system, Mg-AE, in which the eutectic composition is known and in a complex ternary system, Mg-Al-Zn, in which the literature is uncertain as to the composition of the ternary eutectic. The advantages and limitations of this unique approach for the determirution of the eutectic composition are discussed. ThE eutectic composition in phase diagrams is usually determined by thermal analysis of a series of arbitarily selected alloy compositions. The temperatures of the liquidus and eutectic arrests for each alloy are plotted and the eutectic composition is estimated by extrapolation to the entectic temperature of the curve formed by the liquidus arrest temperatures for the series of alloys. Although this approach readily yields the eutectic temperatures, several dekrminations are needed to estimate the eutectic composition, even in a simple system. In a complex ternary system, a great many determinations are often necessary to estimate, even approximately, the ternary eutectic composition. Thus, the conventional method is inherently tedious and time consuming. The application of zone melting provides a relatively efficient method of determining the eutectic composition.&apos; As an illustration, consider the zone melting of an alloy composition C, in the simple eutectic system A-B, shown in Fig. 1, under the ideal conditions of infinitely rapid diffusion in the liquid, no diffusion in the solid, and ease of nucleation of both phases. As the zone moves along the bar, the composition of the zone is enriched by solute rejected during the freezing of the a phase and the zone composition approaches the eutectic composition CE.Once the zone composition attains the lowest melting composition, i.e., the eutectic composition, it remains at this composition as the zone moves along the bar and finally freezes as such at the end of the bar. Chemical analysis of the end of such a zone-melted bar then should yield the eutectic composition CE of the system A-B. A corresponding analysis can be made for a ternary eutectic system. Under the ideal conditions noted above, only one pass of the molten zone is required to yield the eutectic composition. Experimentally, however, a solute-rich layer forms at the solid-liquid interface2 and the composition of the zone does not attain the eutectic composition as rapidly or as uniformly as in the ideal case outlined above. But with agitation of the melt, the ideal conditions can be approximated experimentally. Also, as shown below, zone melting permits a cumulative build-up of the solute at the end of the bar to the eutectic composition. The purpose of this paper is to demonstrate this unique method for determining the eutectic composition. The method is here applied to two systems: first, to the binary Mg-A1 system, in which the composition is well established, and second, to the complex Mg-Al-Zn system in which there is doubt concerning the composition of the ternary eutectic. EXPERIMENTAL PROCEDURE The zone-melting apparatus used in this study is described in detail elsewhere.3 Briefly, the binary alloy rods (5/8 in. in diam and 9 in. long) and the ternary alloy rods (5/8 in. in diam and 6 in. long), with the compositions given in Table I, were zone

Jan 1, 1962