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By W. A. Haley

Wheel loaders were first introduced shortly after World War II as small machines designed for handling loose materials in various industrial and processing applications. It was not until the early 1950?s, however, that machine size permitted widespread loading of loose or stockpiled material into on-highway type trucks. An ever increasing number of machines continue to be used for this purpose today. In fact, it is by far the major use for wheel loaders in mining and quarrying. Many of these loaders were working at mines or quarries handling in-process or finished material and some were doing shovel clean-up. It was quite natural then, when the primary pit loading shovel was down, to attempt to maintain some production by replacing it temporarily with the wheel loaders. Most of these attempts were not very successful, however, until the really large wheel loaders, 4- to 6-yd. size were introduced in the early 1960's. Since that time these machines have proven they can be productive and economical primary pit loading tools, a job that was once the exclusive domain of the power shovel. To be competitive with the shovel however, conditions must exist or be made to exist, that will be favorable for the wheel loader.

Jan 1, 1967

By Raul A. Deju

A theoretical and experimental study was made of the surface phenomena occurring in a silicate - sulfonate system and a silicate -amine system, Experiments were conducted varying the collector concentration to examine its effect both on the total surface sorption and the rate of sorption. The results were compared to a theoretical model based on a Langmuir-type isotherm, Finally, the flotation behavior of selected silicate minerals was predicted from the sorption results and an explanation for the flotation of silicates postulated on the basis of both the theoretical predictions and experimental data.

Jan 1, 1967

By J. G. Walters

This report presents the results of an investigation in Which the chloroform solubilities of coals and chars are related to rank, temperature of thermal treatment, time at a given temperature, vacuum thermal treatment, plasticity, oxidation, blending, and mass spectral analyses and molecular weights of the extracts. It was found that the quantity of chloroform extract obtained from chars can be altered by creating a vacuum above the charge during preparation of the char, increasing the time at temperatures within the plastic temperature range, and by utilizing different rates of heating to attain a given temperature. Relationships found between the chloroform solubilities of chars produced at temperatures within the plastic temperature range and the relative fluidities in this temperature range indicate that the chloroform-soluble portion of the char is a significant component of the plastic mass. Chloroform-extract yields from chars made from blends of coals cannot be calculated from chloroform-extract yields obtained from chars made from the component coals.

Jan 1, 1967

By Alexander E. McHugh

A study of some variables affecting the recovery of molybdenum from oxidized molybdenum minerals was made. The effects of variations in contact time, temperature, pulp density, particle size, and solvent concentration on the recovery of molybdenum using acid and alkaline solvents were investigated. Chemical analyses, screen analyses and microscopic examinations were made and the presence of important elements determined. A hydrometallurgical method was developed to recover the molybdenum from the oxidized molybdenum ore by simultaneous dissolution of the molybdenum with sulfuric acid, adsorption on activated charcoal and flotation of the charcoal. The molybdenum was extracted from the activated charcoal with sodium hydroxide, precipitated with calcium hydroxide as calcium molybdate and this regenerated sodium hydroxide for additional stripping. A solvent extraction method, using mines, was also studied to recover molybdenum from both alkaline and acid molybdenum solutions. Satisfactory results were obtained.

Jan 1, 1967

Jan 1, 1967

By R. D. Hagni

The following is a case study illustrating the use of thin sections and polished sections of crude ore to predict metallurgical response. By examining polished sections of the metallurgical products, the textural and mineralogical reasons for unsatisfactory separation can be explained. An area of oxidized Negaunee Iron-Formation located south of Negaunee, Michigan, in the Marquette Iron Range, has been considered for roast reduction-magnetic separation. Preliminary metallurgical studies and subsequent pilot plant testing produced varied results. These results prompted this microscopic study which began with an examination of 126 thin sections and 82 polished sections prepared from 126

Jan 1, 1967

By A. H. Larson, T. P. McNulty

RECENTLY, an investigation of the absorption of sulfur dioxide gas in molten binary copper alloys was conducted. A Sieverts-type apparatus, consisting of a mercury-filled gas dispensing buret and a mercury manometer, was used initially for determining the volume of gas absorbed as a function of pressure. The equilibration behavior of the alloys studied indicated that the mercury in the gas measuring system was absorbing sulfur dioxide. Owing to the widespread use of mercury as a displacement medium in absorption studies, an investigation was made to determine the nature and magnitude of the mercury - sulfur dioxide absorption effect. The gas measuring system was modified by substituting a Worden Quartz Products Type PDHV fused-quartz-spiral pressure gage for the mercury-filled dispenser and manometer. The dispensed gas volume at known temperature and atmospheric pressure was measured by evacuating a Pyrex vessel of known volume and by admitting sulfur dioxide into the vessel until the attached quartz pressure gage registered atmospheric pressure. Atmospheric pressure was measured concurrently with a separate mercury barometer. The volume of the empty sample chamber and its attendant apparatus was determined by measuring the equilibrium pressure accompanying the addition of a measured volume of sulfur dioxide into the initially evacuated system. The volume of the mercury sample was calculated from the density of mercury at the temperature of the study (25°C). Measured volumes of sulfur dioxide were then dispensed into the system and the equilibrium pressure accompanying each gas addition was determined. From the difference between the system volume and the mercury volume, the number of moles of gaseous sulfur dioxide remaining in the system at each pressure was calculated. The difference between the number of moles of gas dispensed into the system, denoted Enso2: and the number of moles of gas remaining in the system after absorption equilibrium had been attained, denoted nso2(g), was equal to the number of moles of absorbed gas, denoted nSO2. The number of moles of absorbed gas was then converted to absorbed volume, denoted VSo2, in cu cm at stp conditions of (PC and 760 mm Hg. Table I contains calculated values of Snso2, nSo2(g), and VSo2 for different sulfur dioxide pressures. In the original system, denoted Run I, volume limitations of the gas dispensing system prevented absorption studies at equilibrium pressures near atmospheric pressure, so a different gas dispensing system, denoted Run 11, was used for determining the last pressure reading in Table I. The data in Table I are expressed in terms of the absorption of sulfur dioxide in 49.68 cu cm of mercury. In Fig. 1, these data are expressed in terms of the absorption of sulfur dioxide in 100 cu cm of mercury. Since the absorption data plotted in Fig. 1 show a linear relationship, the volume of sulfur dioxide absorbed in mercury is a function of the first power of pressure. The absorption reaction is So2(gas) = SO2 (in Hg) The first-power pressure dependence, coupled with the fact that the sulfur dioxide could be removed from the mercury by applying vacuum, indicated reversible

Jan 1, 1967

By Robert W. Ageton

The Bureau of Mines investigated the in situ vertical component of the rock stress in the rib of the haulage drift on the 6100-level of the Star mine, Burke, Idaho, using the flatjack and borehole deformation methods. The estimate of the vertical component of stress about 2 feet into the rib at a station along the haulage drift on the 6100-level of the Star mine by the flatjack method is approximately 5,875 psi, whereas the borehole deformation procedure at this station yielded a value of 5,500 psi for the same depth into the rib. The test zone is approximately 5,625 feet below the surface.No attempt was made to extrapolate stress estimates beyond the depth of the flatjack installation.

Jan 1, 1967

By D. W. Agers

This paper is an extension of previous work evaluating a new extractant, LIX®-64, for recovery of copper from dilute acidic solutions. Large scale pilot plant operations have confirmed the technical and economic feasibility of the process and, with minor exceptions, scale up parameters obtained by previous laboratory work. Operating problems encountered in the pilot plants are discussed. Design parameters for-scale-up to commercial plants are presented and discussed along with a revised capital cost estimate. The future pilot program is discussed, including minor design changes and the effect of entrained organic on dump leaching efficiency.

Jan 1, 1967

By F. A. Loving

This paper describes experiments which represent an effort to measure preciscly the pressure-time history in detonating condensed commercial explosives. The performance of explosives in mining has been a favorite subject for experimentalists and theorists for many decades. Much useful empirical information has been developed; but it has not yet been possible to predict, or even to account for, the behavior of explosives in mining on the basis of fundamental physical principals. A basic piece of information that would appear necessary for any rigorous analysis is the pressure-time history in the detonating condensed explosive. The experiments described here represent an effort to measure this relationship precisely in commercial explosives. THE EXPERIMENTAL METHOD The experimental method, first described by Cowan and Jacksonl has been extensively evaluated by Cowan and Balchan for relatively simple explosives. The experimental procedure involves the detonation of a layer of explosive between metal plates whose external surfaces are polished to a mirror finish (Fig. 1). Precise measurements of the deflection of

Jan 1, 1967

By R. B. Tippin, J. S. Browning

Inasmuch as the higher grade potash deposits are rapidly being depleted, it is important that economic beneficiation techniques be developed for recovering potassium compounds from lower grade sylvite ores and deposits containing clay materials. The Federal Bureau of Mines has conducted research to develop processes for heavy liquid concentration of potash ores, This method of concentration is discussed, and results of tests made on potash ores from New Mexico are presented. The tests demonstrated the technical feasibility of producing near commercial-grade potash concentrates, with a high recovery of the contained sylvite. The concentration of minerals based on their differences in specific gravity dates back to the very beginning of mineral dressing, and the use of heavy liquids in the laboratory to achieve optimum mineral separations has been utilized for many years. With the advent of froth flotation and its success, the incentive to develop new processes has remained relatively dormant. However, flotation refinements in the nonmetallic ores have not progressed as rapidly as in metallic (sulfide) ores because of the complexity of the deposits and the chemical similarities of the minerals.

Jan 1, 1967

By Robert E. Green, T. Hinton

Expressions are derived for tke orientation factors appearing in the Grana to -Lucke theory of dislocation damping, for fcc crystals. The factors are given as functions of the elastic constants, the direction cosines of the specimen axis, atld the direction cosines of the particle displacemeizts, for darnping due to dislocation motion on each of the twelve possible slip systems as ixell as lor simultaneous dislocation rnotion on all twelve systems. RECENTLY Green' has outlined the general procedure for calculation of the modes of wave propagation in a single crystal possessing a given crystallo-graphic orientation. In addition he has suggested how the results of such calculations along with calculations of the resolved shear-stress factors for slip enable the orientation-dependent factors (orientation factors) appearing in the Granato-Lucke theory of dislocation damping to be calculated. However, reen' assumed that the maximum stress on dislocations was in the direction of the particle displacement of the elastic wave giving rise to the dislocation damping. The present cal'culations show that this is an oversimplified approach appropriate only to special cases of high crystallographic symmetry. The exact calculation of stress on the dislocations can only be obtained by resolving the nine components of stress associated with the elastic wave into the appropriate slip direction and then summing. In this paper the general expressions for orientation factors are derived for fcc crystals in terms of the elastic constants, the direction cosines of the particle displacements, and the direction cosines of the specimen axis, bearing in mind the point mentioned above. Equations are presented which give the orientation factors for damping due to dislocation motion on each of the twelve possible slip systems as well as for simultaneous dislocation motion on all twelve systems arising from elastic-wave propagation. These orientation factors are appropriate to attenuation measurements made by the pulse-echo technique, where the elastic wave is a traveling wave. They will be compared with those for the case of a standing wave as derived by Granato and Lucke which are appropriate to measurements of internal friction by the resonance technique. The expressions for the orientation factors are compared with the five values given by insruch,' based on unpublished work of Granato and Liicke, for positions of highest symmetry in the stereographic triangle. The various equations derived for modes of wave propagation and orientation factors have been evaluated for the case of aluminum crystals at 1-deg intervals throughout the stereographic triangle. These results will be presented in the form of contour diagrams in a subsequent paper3 and their relevance to ultrasonic measurements discussed. ORIENTATION FACTORS The coordinate system used for the calculations is shown in Fig. 1 and all specimen axes are taken to lie in the shaded standard triangle. The twelve slip systems are indexed according to Table I. Following the suggestion of lers, we may define the orientation factor Ok in the Granato-Liicke theory5 by the equation

Jan 1, 1967

By D. A. Keyes

International Minerals & Chemical Corp. (Canada) Ltd. is presently exploiting by underground mining a potash-rich zone in the middle Devonian Prairie Evaporite formation near Esterhazy, Saskatchewan. Of the three main potash-bearing horizons denoted by Goudie as zones 1, 2 and 3 only the 1ower. two are present at Esterhazy and mining is confined to the lower or zone 1 horizon. The area in which the evaporites were deposited, although flanked on the west by a zone of geosynclinal deposition and tectonic activity, has been subjected to only very gentle epeirogenic activity. The sylvinite ore is coarsely crystalline and occurs in well-defined beds. The halite, sylvite and insoluble content of the ore bears a direct relationship to the lithological units, but the carnallite cuts across the beds. Local concentrations of salt produce blank spots in the ore horizon. Some of these appear to be salt-filled, post-ore channels and cracks while others have been formed by brines emanating upward from below the ore. INTRODUCTION International Minerals & Chemical Corporation (Canada) Ltd. is operating an underground potash mine near the town of Esterhazy in eastern Saskatchewan. The deposit was discovered by IMC in 1955. Subsequent drilling outlined extensive high-grade reserves, and in 1957 shaft sinking and plant construction began. Production from Yarbo No. 1 Shaft commenced in September, 1962 and quickly reached the initial capacity of one million tons of muriate product per year. Production is currently being expanded to 1.6 million tpy. The single mining level is 3140 ft below the surface at No. 1 Shaft. GENERAL GEOLOGY The Esterhazy district lies within the Interior Plains region of Canada and on the northeast rim of the Williston Basin (Fig. 1). Average dip of the rock formations in this area is about 40 ft per mile to the southwest. The potash ore occurs in the Prairie Evaporite formation of the Middle-Devonian Elk Point Group. The Prairie Evaporites are overlain by 3000 ft of Paleozoic shales and limestones and by Jurassic and Cretaceous sandstones and shales (Fig. 2).

Jan 1, 1967

By Stewart W. Daniel

"Increasing labour costs, the trend to larger mills, the processing of lower grade ores and a diminishing sup-ply of well-trained and experienced mill operators contribute to the necessity of automating a grinding circuit. With sophisticated process control techniques, supervision of the mill line is reduced to an occasional inspection by the shift supervisor. Process operating decisions and/or adjustments are quickly and accurately performed by the electronic devices to be described. When the variables in the grinding circuit are stabilized using the sensors and controllers as discussed, the over-all grinding circuit is maintained at its optimum grinding load level, with ample protection against under-and overloading."

Jan 1, 1967

By G. G. Hancock, H. H. Johnson

Hydrogen gas at atmospheric pressure is shown to cause substantial embrittlement in a martettsitic high-stretzgth steel. Subcritical crack growth is observed at very lom stresses and with high growth rates. It is suggested that an adsorbed layer of hydrogen atoms at the crack-tip surface provides the damaging hydrogen. Oxygen in small quantity, as little as O.7 pct by volume, is shown to eliminate subcritical crack growth in gas environments caused by hydrogen or water vapor. However, dissolved oxygen in water has little or no influence upon crack-growth rates. Oxygen-stopped cracks may be restarted by water, or by hydvogen or water vapor if oxygen is removed from the environment. These observations are interpreted in terms of preferential adsorption of oxygen at the crack tip and the formation of an oxide barrier. RECENT investigations1-3 have demonstrated that environmental factors are frequently responsible for delayed failure in martensitic high-strength steels. The environment causes crack initiation from preexisting cracklike flaws at unexpectedly low stresses, often far below the uniaxial yield strength. The crack then propagates at a rate controlled by the environment and the crack-tip stress-field intensity; during this period crack propagation will cease if either the stress or the aggressive environment is removed, and this may be considered a definition of subcritical crack growth. Fracture occurs when the crack has grown to a critical length, such that the fracture toughness of the steel is exceeded. Several liquids are known to cause delayed failure, but water and water vapor are the most severely damaging of the environments investigated to date.'-3 It has been suggested that hydrogen produced during corrosion reactions may be the actual embrittling agent2 The severe embrittlement caused by water vapor inevitably raises the question as to whether other gas environments are damaging. Previous work4'5 has demonstrated that high-pressure hydrogen (2250 psi or greater) is an effective embrittling medium, as measured by such criteria as reduction in area, notch tensile strength, and time to failure. Moreover, the embrittlement was eliminated by the addition of small quantities of air or oxygen to the high-pressure hydrogen, but it was not influenced by additions of nitrogen or argon.4 In the present study attention is focused upon gas environments at atmospheric pressure, in particular hydrogen and oxygen. The influence of these constituents upon the initiation and growth of a crack from a pre-existing cracklike flaw in a high-strength steel was determined directly by the electric-potential method of monitoring crack growth. MATERIALS AND PROCEDURE The H-11 steel was supplied by the U.S. Naval Research Laboratory as 3 by 12 by 0.065 in. sheet specimens with 1-in. transverse center slots. The slot tips were finished by Elox machining to a radius of 0.001 in. or less. The yield strength was 230,000 psi; chemical composition and heat-treatment schedule are given in Table I. The experimental apparatus, precracking procedure, and incremental loading sequence have been described previously.3 In the only significant change, precracking was sometimes carried out by a hydrogen embrittlement and baking technique. All experiments were conducted at room temperature; the hydrogen gas environment was purified by a commercial palladium purifier. Crack initiation and propagation were followed by the electric-potential method,'-3 using a calibration that has been recently dicussed. Stress-field intensities at the crack tip were computed by the conventional Irwin frmula; the plasticity correction was negligible and therefore not included. EXPERIMENTAL RESULTS A striking brittleness associated with molecular hydrogen at atmospheric pressure is demonstrated by the data in Table I1 and Fig. 1, which indicate that subcritical cracks in hydrogen initiate at lower stress-field intensities and propagate more rapidly than in fully humid argon. Ki and Kf are the crack-tip stress-field intensities at initiation and termination of subcritical crack growth, respectively. Termination, of course, corresponds to fracture. In both hydrogen and humid argon Ki is less than Kf

Jan 1, 1967

By R. W. Thompkins

In order to evaluate the impact of air quality control on mine design, a few examples are given of cases in wh.ich ventilation has affected the economics of the total design problem. Principles for the drainage of gas contaminants are shown, and the contamination control problems created by differential pressures in complicated booster fan installations are discussed. The paper also deals with the use of advanced mathematics for solving some of the ventilation problems likely to be encountered.

Jan 1, 1967

Jan 1, 1967

By Gerard C. Gambs

The electric utility industry is the largest customer of the U.S. coal industry, consuming nearly 50% of present coal production. By 1980, the electric utilities are expected to burn over 500 million tpy of coal or 75% of total coal production. When coal is burned in electric utility plants, ash is produced in one of several forms. These include fly ash, bottom ash and bottom slag. At the present time, approximately 20 million tons of these ashes are produced and must be disposed of by the utilities at a cost of 50[c] to $2 per ton. In 15 years, more than double this quantity will be produced. Only a small quantity of this ash is put to any practical use. Much remains to be done about expanding uses for fly ash and bottom slag.

Jan 1, 1967

By L. Weyher, H. L. Lovell

This discussion is restricted to a very specific application of the cyclone - its use as a hydro-cyclone in the cleaning of fine coal. It is hoped that the development of the present data will assist in the further elucidation of existing qualitative models, and also in an enhanced application of the hydrocyclone and provide a base for further research. Discussed are the mechanisms of gravity separation in hydro-cyclones, test procedures, experimental observations, and industrial applications from these studies. Within the general area of unit operations, a considerable effort has been expended in theoretical and empirical research associated with cyclone operations. The motivation involves the industrial requirement for devices and techniques to manipulate small particles at low operating costs, a situation required in coal preparation. There are good reasons why the cyclone helps to satisfy this demand, because it combines operational simplicity (no moving parts) with versatility and high throughput capacity per unit area. The cyclone is one of the most widely applied tools in the process technologies. There are areas for potential cyclone application which have been only meagerly explored or not considered at all. This discussion is restricted to a very specific application of the cyclone - its use as a hydrocyclone in the cleaning of fine coal. It represents an initial presentation of a more comprehensive report. Coal preparation can appropriately claim the hydrocyclone since most of its predominant industrial uses have originated in this area and have spread into other applications, including the broad field of ore dressing, the petroleum industry, chemical processing, nuclear engineering and food technology. There is one operational principle common in all cyclones: A fluid is tangentially introduced into a cylindrical or conical container under pressure. A predominantly irrotational flow field1 is established within the cyclone (Fig. 1). The uniqueness of this flow is indicated by the variation in tangential velocity across the cyclone radius, which reaches a maximum a short distance from the center and decays toward the cyclone wall. In contrast, the tangential velocity in a centrifuge increases uniformly toward the wall. Usually two products are discharged from the cyclone. They differ in that one discharge consists predominantly of that portion of the feed fluid which moves along the wall axially away from the feed inlet, while the other consists predominantly of fluid spiralling along the central regions of the cyclone, in an axial direction opposite to that of the wall current. Fig. 2 indicates these discharge points schematically. The latter product may be termed the vortex-product, since it is discharged with the central vortex-current. In the case of conical cyclones, the former product may be referred to as the apex-product. Although the names "over- and underflow" are widely used, many cyclones are operated from extreme angular positions thus the proposed terms are less ambiguous. The cyclone feed fluid can be laden with solid particles or nonmiscible fluid drops. Such a feed component is discharged from the cyclone, after some residence time, into the one or the other product. Yet, the orifice through which a particle will leave the cyclone is dependent upon a number of factors. These factors, in a statistical sense, determine the path of the particle within the cyclone. Thus, different separation phenomena are possible and different process results attainable by the controllable variation of the particle path. It is then, to attain a fuller understanding of this particle path, to which this study is ultimately directed. It is anticipated that the detailed study of the data being developed will allow further elucidation of existing qualitative models. However, the development of a quantitative description of cyclone operation in terms of a mechanism is not currently feasible. The flow conditions in a cyclone are not fully understood even for a pure fluid, without the added complexity of the inclusion of multiple size-density particles. It is hoped that the development of the present data will also assist in an enhanced application of the hydro-cyclone and provide a base for further research. Some practical applications drawn from the data are suggested. Cyclone operations have been classified according

Jan 1, 1967

By B. W. Roberts, V. A. Phillips

A copper alloy containing- 25.5 at, pct Zn and 19.0 at. pct Ni, which was previously found to show an anoma1old.s hardening effect on quenching- from 600 "C and aging- at 400oc, has now been examined by neutron diffraction. No evidence of long-range order was found. The aged sample showed diffuse scattering- consistent with clustering. The anomalous hardening effect is now attributed to lattice strains caused by clustering rather than (long-range) order hardening. SOLID-solution Cu-Ni-Zn alloys (the commercial 'nickel silvers") have been reported to show anomalies in: change of resistivity on cold working,1-6 temperature coefficient of resistance,2-12 resistivity at low temperatures,13,14 parameter (vs temperature),2"4 calorimetric data,2,4 specific heat,15,16 dilation,2-4 and elastic modulus.17 The structure responsible for the anomalies is produced by annealing typically near 400°C and is rather loosely referred to as the ('K-Zustands" (K state), a term coined by Thomas1' who apparently meant simply that the arrangement of atoms on the sites deviated from that expected statistically. Thomas proposed that the K state occurred in a variety of (solid-solution) alloys such as Cu-Ni-Zn, Ni-Cr, Ni-A1, Ni-Cu, Fe-A1, and Fe-Si and is recognized because its formation is strongly temperature-dependent and results in an increase in electrical resistance which can then be decreased by cold working. Later workers on ('nickel silver" have interpreted the K state variously as short-range order, long-range order. or a combination. The present work was prompted by the discovery by Phillips and Jones19 of a substantial hardening effect when an 18 pct "nickel silver" alloy which is fairly close to the Cu2NiZn composition, was reheated in the range 150" to 450 C after previously quenching from 600°C or, alternatively. was slow-cooled from 600°C or above. The phenomenon was attributed to (long-range) order hardening. Due to the similarity in the atomic scattering factors of copper. nickel, and zinc atoms, the ''nickel silvers" are unfavorable for X-ray diffraction studies aimed at detecting ordering. Nevertheless Bialas et a1.,20 using a powder sample containing 47.96 wt pct Cu, 24.03 wt pct Ni, and 27.98 wt pct Zn, slow-cooled from 400" to 200°C taking 500 hr, observed weak super lattice lines. Further unpublished work" using an anomalous dispersion X-ray technique indicates that zinc atoms are regularly ordered at the corner points of the lattice cell, while the nickel and copper atoms are statistically distributed on the remaining sites. Köster 17 also observed X-ray superlattice lines, for example, in an alloy containing 43.5 wt pct Cu, 28.6 wt pct Ni, and 27.9 wt pct Zn superimposed on the basic fcc cell with a = 3.62 kX. He proposed a Cu3Au-type superlattice with the Ll2 structure in which the A sites were statistically occupied by copper and nickel atoms and the B sites by zinc. He adds that substitution must be possible so that zinc atoms partly occupy A sites. Below about 35 pct Cu, Koster had some evidence for a CuAu-type superlattice with the Llo tetragonal fcc structure with a = 3.82 kX, c/a = 0.88 which could be preserved by quenching. This is suggested17722 to correspond to CuNiZn. While the present work was in progress Hirabaya-shi et a1.23 made an independent comprehensive neutron-diffraction study of a single crystal containing 50.05 at. pct Cu, 26.57 at. pct Ni, 0.25 at. pct Mn, 0.13 at. pct Fe, balance zinc. The presence of manganese and iron is surprising since the crystal was supposedly grown from high-purity metals. The homogenized crystal showed evidence of long-range ordering after an anneal of 5 months at about 300°C. Three possible crystal models were proposed. A curious feature of their results23 is that they could not find any neutron-diffraction evidence of ordering in a powdered polycrystalline near-stoichiometric Cu2NiZn alloy. There appears to be some essential difference between a near-stoichiometric Cu2NiZn alloy and one somewhat further off stoichiometry as used by the present authors. Thus Sato14 was able to reproduce the low-temperature resistivity anomaly reported by one of the authors13 on the present alloy if he used a similar composition, but found the normal behavior of the residual resistivity in a near-stoichiometric alloy. satol2 found that the resistivity of a cold-drawn slightly off-stoichiometric alloy increased to a maximum on isothermally annealing at 300°C and then decreased ("over-aged"). Since he could not explain this on the basis of ordering phenomenon, he proposed that zinc atoms were segregating to stacking faults (Suzuki effect) and found etching bands on the surface by replication which were attributed to the widening of faults. Sato suggested14 that the hardening effect observed by Phillips and Jones19 is partly due to the Suzuki effect. EXPERIMENTAL The starting material was 1/4-in.-diam hard-drawn rod of a commercial 18 pct "nickel silver" alloy identical with that used in a previous study by Phillips

Jan 1, 1967