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By Erik Q. Dahl

The strength of green and sintered pellets during reduction under various conditions in a laboratory kiln has been investigated. Equipment and test methods are described, together with the results obtained. The strength of sintered pellets drops sharply when the reduction starts, and goes through a minimum at the 70 per cent oxidation level. At more advanced reduction, the strength increases with increasing metallization. Successful use of green pellets as kiln feed requires that more attention be paid to the pellet preparation than is necessary when producing pellets for separate sintering. In particular, the ores have to be ground to a greater fineness. The initial strength of green pellets is low. Below the 70 per cent oxidation level, however, the strength of these pellets is about the same as the strength of sintered ones. Additions of such materials as silica, limestone and anthracite coal; within reasonable limits, affect the strength only slightly.

Jan 1, 1966

By M. H. Haycock

Introduction The property of Rouyn Merger Gold Mines, Limited, is in Rouyn and Joannès townships, Western Quebec, seven miles east of the town of Rouyn. Traversing it is the east-west trending Cadillac-Bouzan fault. Diamond drilling in 1944 and 1945 along a shear zone south of the fault indicated an ore deposit lying at the contact between sedimentary and volcanic rocks and dipping approximately 60° to the northwest. In the summer of 1945 it was decided to sink a shaft to investigate the indicated ore zone. In the immediate vicinity of the deposit, bed-rock is overlain by clay beds, in some places as much as 70 feet thick. Consequently, possible shaft sites were limited to those locations where overburden would not be excessive. The most favourable site was about 125 feet to the south of the ore zone as projected vertically from bed-rock to the surface. Accordingly, it was decided to sink the shaft at this point, with an inclination of 60° N. W., paralleling the dip of the ore zone.

Jan 1, 1948

By Gerrit V. R. Goodman

In This Chapter [Design and operation of machine-mounted scrubbers Dust control with scrubbers and blowing ventilation Dust control with scrubbers and exhaust ventilation Dust control with exhaust ventilation and no scrubber Dust control methods common to all continuous miner sections Dust control for roof bolters] This chapter explains how to control dust at continuous miner sections in coal mines where the main dust sources are continuous miners and roof bolters. In relation to dust, there are three categories of continuous miner faces depending on the type of ventilation and whether or not a machine-mounted dust scrubber is used. These are— 1. Mining machines with dust scrubbers used with blowing face ventilation 2. Mining machines with dust scrubbers used with exhaust face ventilation 3. Mining machines without scrubbers used with exhaust face ventilation The approach to dust control is somewhat different in all three of these. However, there are many dust control features (such as the need to provide adequate airflow) common to all continuous miner sections. For workers at roof bolter faces, there are two dust sources: 1. Dust from the continuous miner when it is upwind. 2. A malfunctioning dust collector on the bolter, which allows dust to escape DESIGN AND OPERATION OF MACHINE-MOUNTED SCRUBBERS [Almost all new continuous miners are equipped with scrubbers. When the dust is excessive, it is possible that the scrubber needs some maintenance.]

Jan 6, 2003

By T. W. Peglas, J. Doherty, R. A. Day

The South East Transit Project is a $520 million project in Brisbane, Australia which includes the construction of a 32 km Busway to access the south-eastern suburbs. Close to the centre of Brisbane, tunneling techniques have been used to minimise surface disruption. This paper describes some of the features of the longest driven tunnel on the project, the Vulture Street Tunnel. The Busway is a two lane expressway for buses which requires a 10.2 m finished width and a 12.6 m excavated span of driven tunnel. The Vulture Street Tunnel carries the Busway at minimal cover beneath the operating Vulture Street Railway Station, beneath a three storey office building and beneath the roadway to the Mater Hill Busway station. Halfway along the route, a Y-junction has been constructed to enable future connection with a light rail route. Key features in the design and construction of the Vulture Street Tunnel include: Use of canopy tubes to drive a 12 m wide tunnel beneath operating railway tracks with less than two metres of cover in highly weathered rock. Underpinning the office building in the route of the tunnel construction from within the building carpark. Construction of a 24 m span Y-junction with 7 metres cover of weathered and faulted rock. Use of predictive analysis as an adjunct to traditional back analysis to estimate the tunnel settlements from pressuremeter test results. This paper describes the design methodology with particular reference to settlement prediction, as well as construction innovations used to complete the tunnel. This paper will be of interest to all designers who have to create large spans in minimal cover in weak rock in urban areas and who have to predict the settlement

Jan 1, 2001

By D. Larouche, M. Mardan

Hot tearing is a complex defect in aluminium castings which is produced during solidification when a certain amount of liquid phase remains and weakens tensile resistance of the alloy. In direct chill casting of aluminium alloys, hot tears initiate at the surface of sheet ingots just after the primary cooling zone, where the microstructure is particularly vulnerable. In order to study the hot tearing susceptibility of these alloys, and the effect of grain refiners on their thermo-mechanical behavior , tensile tests were carried out in the semi-solid state ( ~95% solid) and at low strain rates using an apparatus called DCSS, for Direct Chill Surface Simulator. This apparatus, originally developed at Alcan Arvida R&D Centre (ARDC), is an instrumented rig test reproducing the conditions prevailing during the primary cooling stage of the DC casting process. The mechanical behavior of solidifying shells and the hot tear formation under applied tensile loads were measured and the occurrence of hot tearing was observed. Temperature in different locations of the casting, applied load and surface strain were monitored during the tensile tests conducted on aluminum alloys AA5182, AA6111 and AA3104. The microstructure of the tested samples was examined using the optical microscope to evaluate their columnar or equiaxed aspect and their effect on the mechanical response of the alloy. A special emphasis has been given to the evaluation of fractions solid existing in the castings at the start of the tensile tests, taking into account the local temperature, thermal gradient and cooling rates experienced. It was found that excessive grain refiner additions decreased the strength of solidifying shells because of the increased level of porosity induced by easier nucleation of new phases (gas included). It was also observed that cooling rates increased with the level of grain refiner, a phenomenon that was associated to the higher number of contact points obtained with small equiaxed grains. Finally, the concept of a stress based criterion for hot tearing was reinforced by the strengths obtained on not grain refined AA5182 and AA6111 showing similar fraction solid near the surface, but significantly different grain sizes.

Jan 1, 2006

By Wai Ng, Fluquer Peña, Elvis Sanchez, Inés Trinidad

Las unidades sedimentarias mesozoicas que afloran en las subcuencas Apurímac, Vilcabamba y Santo Tomás se encuentran asociadas a una clasificación hidrogeológica (acuíferos o acuitardos fisurados sedimentarios). La caracterización litogeoquímica de estas unidades sedimentarias se basó en los 15 elementos (As, Cr, Cu, Fe, Mn, Ni, Se, Zn, Be, Cd, Hg, Pb, Sb, Sn, Ti) que utilizan los estudios de línea base geoambiental del Ingenmet. Los resultados han sido comparados con los valores de la UCC (Wedepohl, 1995), lo cual ha permitido caracterizar el comportamiento químico de las unidades hidrogeológicas asociadas a las unidades sedimentarias. Se determinó que son tres los factores que controlan el comportamiento químico de las unidades hidrogeológicas: tiempo geológico, espacio y litología. Estos factores son importantes para la integración de información con los análisis de sedimentos y aguas de los estudios de línea base geoambiental, porque permitirán comprender el origen de posibles zonas anómalas de los elementos descritos en los sedimentos y aguas.

Sep 20, 2019

By Ahmad Abdollahi

Many factors affect mechanical properties of hypoeutectic Al-Si alloys. As examples the presence of impurities such as Mn and Fe due to the formation of intermetallic phases, additions of small amounts of alkaline earth metals and cooling rate in consideration of Si formation, they all have an impact on mechanical properties of hypoeutectic Al-Si alloys. In this investigation, the effect of Fe content into the specification range of A357 alloy, the addition of different modifiers consisting of Na, Sr and Ca for the alloy of A356 and different mounting techniques for separately cast test coupons of hypoeutectic Al-Si alloys using the lost wax method were studied. The results showed that using material with lower Fe content and addition of modifiers improve mechanical properties. Also different mounting techniques resulted in different mechanical properties.

Jan 1, 2004

By Etienne Audibert

No satisfactory theory has yet been advanced to explain what takes place when an explosive is fired in a mixture of firedamp and air. The only means of measuring the danger is to fire the explosive into the gas mixture and note the effect, but the conditions of firing must be chosen carefully. This report is presented in the hope that it will assist in determining what method to use. The experiments have been designed to show the effect of the principal factors involved in the conditions of firing, and the results give information that seems to have some value.

Jan 1, 1940

By Nixon C. A

The exploration of Mount Isa Mines' new copper source will require the development of a five kilometre 4.7 x 5.5 metre blind decline commencing 1000m below the surface and extending to 1600m below the surface. With virgin rock temperatures approaching 60¦C, the ventilation strategy represents a complete departure from any previously used at this mine, in that refrigeration becomes essential. The use of direct water to air cooling techniques has become commonplace in mines throughout the world and their application is being adopted at Mount Isa Mines. A heat load simulation routine has been implemented to allow for the design of refrigeration requirements, as well as to aid in the selection of diesel or electric equipment. This enabled planners to determine the size of a surface based refrigeration plant. Future refrigeration demand for expansion into the ore production stage has also been investigated.

Jan 1, 1988

By P Shen, K Hattori, H Pan, E Seitmuratova

"An EXTENDED ABSTRACT is available for download. A full-length paper was not prepared for this presentation. Ore-bearing intrusions in the Central Asian Orogenic Belt (CAOB) were examined from nine mines: Boshekul, Nurkazgan, Kounrad, Borly, Aktogai, Koksai, Baogutu, Tuwu and Erdenet. The intrusions are diorite, granodiorite and tonalite with SiO2 contents ranging from 58 to 75 wt per cent, and show mildly fractionated rare earth elements (REE) ([LREE]N/[HREE]N = 2.7–4.7) – light REE and heavy REE – and varying Eu anomalies ([Eu]/[Eu]* = 0.58–1.4). The ratios of Sr/Y vary from 7.9 to 115 and the contents of Y from 4.6 to 23.9 ppm. The parental magmas of the intrusions are intrinsically oxidised. Zircon grains in the ore-bearing rocks from large- and intermediate-sized porphyry Cu deposits show high Ce4+/Ce3+ ratios characterised by 65–422 at Boshekul (>4.1 Mt Cu), 76–480 at Kounrad (>4.8 Mt Cu), 90–280 at Aktogai (>12 Mt Cu), 80–250 at Erdenet (>11 Mt Cu) 74–370 at Nurkazgan (>3.9 Mt Cu), 100–210 at Koksai (>1.6 Mt Cu), and 71–340 at Tuwu (~2.0 Mt Cu). In two small deposits, the ore-bearing rocks display low values of Ce4+/Ce3+; Borly (0.6 Mt Cu) ranging from 28 to 158, and Baogutu (0.6 Mt Cu) from 29 to 113. The Ce4+/Ce3+ ratio of 120 distinguishes large intermediate-size deposits from small-size deposits. This information is potentially useful in exploration for porphyry Cu deposits in the belt.CITATION:Shen, P, Hattori, K, Pan, H, Jackson, S and Seitmuratova, E, 2015. Granitoids associated with porphyry Cu deposits in the Central Asian Orogenic Belt – characteristics and oxygen fugacity, in Proceedings PACRIM 2015 Congress, pp 377–382 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Mar 18, 2015

By Jiang Diao, Yong Qiao, Xuan Liu, Tao Zhang, Bing Xie

Adding CaO into the vanadium extraction converter is an effective way to decrease the dephosphorization burden in subsequent steelmaking process. The crystallisation process of spinel is one of the most decisive factors in the subsequent extraction. The theoretical calculation results show that the temperature of the peak total crystallization rate will decrease 5K with basicity increasing 0.1. The relation between cooling conditions and grain size of spinels is also discussed. It is found that low cooling rate and high basicity benefit spinel crystal growth. And the non-isothermal crystallization kinetics results indicated that the restriction factors of spinel growth is that solid crystals accept new components from liquid-solid interfacial. While the sample was cooled down to 1250 (1523K) at cooling rate of 5K/min, the crystal growth is consistent with Ostwald coarsening grew up law, and controlled by diffusion of particle.

Jan 1, 2016

By D. E. Larson

The U.S. Bureau of Mines investigated Fe-base alloys containing 8 pet Crwith Ni, AI, and Si additions as substitutes for standard AISI Type 304 stainless steel (SS) in high-temperature oxidizing applications. The objective of this study was to reduce the amount of Cr required to make an austenitic stainless steel while retaining satisfactory workability, mechanical properties, and oxidation resistance. Alloys prepared in this investigation had a composition of Fe-8Cr-lMn-0.07C with varying amounts of Ni, AI, and Si. A minimum of 10 pet Ni was required to achieve an austenitic composition. The microstructures of the austenitic alloys were very susceptible to room-temperature, deformation-induced martensitic transformations. When the alloys were cold worked or stressed, the materials had far greater tensile strengths than Type 304 SS at room temperature. At higher temperatures, tensile strengths and workability of several of the alloys were comparable to that of Type 304 SS. Although martensitic transformation caused the room-temperature properties of the experimental alloys to be quite different than those of Type 304 SS, the superior oxidation resistance and similar hot workability of several alloys encourage their use as replacements for Type 304 SS.

Jan 1, 1989

In several European countries, including Russia, it has become economically attractive to utilize peat as a fuel for power generation, the production of metallurgical coke, the production of fuel briquettes for the domestic market and low-Btu gas. Although the economic base and availability of energy supplies in Europe is much different than it is in Canada, regional economics here may warrant the development of peat as an alternative source of energy. Canadian peatlands cover several thousands of square miles and have historically been considered as waste land. Now, with the increasing costs of other energy sources, it is apparent that fuel peat should be re-evaluated as a potential energy resource. A nation-wide inventory of peat deposits has been prepared and reserves evaluated for some of these areas where field surveys have been carried out. The paper describes alternative mining methods developed to meet some of the various conditions encountered on virgin peatland . These mining techniques are generally based on current peat technology exercised in other parts of the world and would be applicable in some of the peat regions of Canada. Cost estimates have been prepared for peat production in regions of Canada, and the socio-economic aspects of a large-scale fuel peat operation are discussed. Several potential utilization schemes have been described, with particular emphasis on electric power generation. The paper makes recommendations for steps to be taken in the development of a fuel peat industry in Canada.

Jan 1, 1978

By Renate Wellen, Olgun Guven, Mariane Y. T. Oide, Julyana Satana, Francisco Valenzuela-Díaz, Esperidiana Moura

Poly[(ethylene)-co-(vinylacetate)] (EVA) is a thermoplastic copolymer composed of randomly distributed polyethylene and polyvinyl acetate sequences within the molecular chain. EVA combines toughness with excellent flexibility, impact and puncture resistance. Because of these properties, this material is largely used for foam production as padding in equipment for various sports and as a shock absorber in sport’s shoes. This work aims to study the influence of clay reinforcement on the performance of recycled polymer foams. The blend containing recycled HDPE (high density polyethylene) and recycled EVA (70/30 wt%, respectively) reinforced with 2 wt%of clays were prepared by melt extrusion, using a twin-screw extruder to obtain the composites. The composites and foaming agent were fed into a special single screw extruder for foaming. The samples of HDPE/ EVA/Clay foams were characterized by tensile test, Field Emission Scanning Electron Microscopy (FE-SEM), Thermogravimetric Analysis (TG), Differential Scanning Calorimetry (DSC), X-ray Diffraction (XRD), density measurement and the correlation between the results was evaluated.

Mar 1, 2018

By Keith A. Heasley

Numerous different instruments and techniques have been developed for the purpose of measuring rock stress and stress changes around excavations. The interpretation of the output from many of these instruments has often been problematic. This paper covers the research performed in attempting to analyze one particular stress measuring instrument called the Borehole Platened Flatjack (BPF) . The approach used in this analysis was to combine the analytical solution for the displacements around a borehole and the analytical solution for the bore- hole-platen interaction with the empirical stiffness behavior of the flatjack. The resulting model of the BPF response was then verified using measured laboratory data with very good results. In addition, techniques for applying the method to the field are briefly discussed. The major accomplishments of this comprehensive modeling and testing program are; 1) the establishment of the critical installation and site parameters of the hydraulic pressure cell and 2) the development of a systematic procedure for calibrating the cell based on the given values of these critical parameters.

Jan 1, 1989

By Tasuku Fuwa, John Chipman, David H. Kirkwood

Fe-C-Si alloys in silica crucibles were held at 1600°C in a controlled atmosphere of CO and Co2 and the approach to equilibrium was obsertsed. Results were not of sufficient precision to establish the activity and interaction coefficients. Observations 012 the equilibrium provided an average value for the standard free-energy change which differed by + 1.1 kcal from the earlier accepted value. The C-SL relation at other temperatures is calculated and shown graphically. IN the refining of steel in an acid-lined furnace, it is well known that, unlike in basic refining, a very significant amount of silicon may remain dissolved in the metal even when the carbon content approaches a final endpoint. Further, it is known that the residual silicon increases with increasing temperature. The quantitative relation between silicon and carbon can be calculated for equilibrium conditions from data already available on the Fe-C-O and the Fe-Si-O systems. Such equilibrium calculations could show us approximately the limitations within which the reaction would be expected to operate in practice. In the oxidation of a bath containing both carbon and silicon it is well known that at low temperatures silicon is preferentially oxidized first. It can be shown by calculation that at high temperatures carbon will be oxidized preferentially. It is the purpose of this paper to record direct observations on the Si-C relation by means of experiments carried out in an atmosphere of carbon monoxide for Fe-C-Si alloys contained in silica crucibles. When such a system is brought into equilibrium, at a fixed temperature, the composition of the liquid metal is governed by the following equations: Both K1 and K2 are known with a fair degree of accuracy, and may be calculated from the tabulated In general the percentage of CO2 is extremely small compared to that of CO and in the experiments to be described the partial pressure of the latter was generally only slightly below 1 atm. EXPERIMENTAL METHOD The induction furnace employed was the same as that described by Rist and chipman' and by Fuwa and chipman.2 It was modified slightly in view of the change from alumina to silica crucibles. The small silica crucible was surrounded by a thin susceptor of molybdenum sheet which in turn rested inside a zirconia crucible. Since the zirconia was subject to breakage, it was supported inside an alumina crucible. The charge consisted of 30 to 35 g of electrolytic iron along with the required amounts of refined silicon and graphite to produce a melt of required composition. Purified carbon monoxide and carbon dioxide were passed into the furnace through carefully calibrated flow meters. Two separate and independent series of experiments were carried out. In Series I (D.H.K.) the melt was held in the furnace at 1600°C for periods of time up to 6 hr. Samples were taken at intervals in silica tubes and were analyzed for carbon and silicon. The results of the last one or two samples taken from each experiment and the direction in which equilibrium appeared to be approached are shown in Table I. In Series II (T.F.) the silica crucibles were of less satisfactory strength and the melts were held at 1600° C for periods of only 2 to 4 hr. In heats number 29 to 45 inclusive, the metal was cooled in the furnace and the ingot itself served as a sample for analysis. In heat 46 and all subsequent heats, samples were withdrawn in silica tubes at the termination of the heat, and these samples were analyzed. The results of all of these experiments in which equilibrium appeared to be approached are listed in Table II.

Jan 1, 1965

By Iam Pou Ng

Combustion aerosols consist mainly of elemental and organic carbon (EC and OC). Since EC strongly absorbs light and thus affects atmospheric visibility and radiation balance, there is great interest in its measurement. To this end, the National Institute for Occupational Safety and Health (NIOSH) published a standard method to determine the mass of EC and OC on filter samples. Another common method of measuring carbon in aerosols is the aethalometer, which uses light extinction to measure "black carbon" or BC, which is considered to approximate EC. A third method sometimes used for estimating carbon in submicron combustion aerosols, is to measure particle size distributions using a scanning mobility particle sizer (SMPS) and calculate mass using the assumptions that the particles are spherical, carbonaceous and of known density. With an eye toward evaluating the use of these methods for measuring carbon in freshly emitted diesel aerosols, the objective of this paper is to compare the results among these methods and to investigate the role of OC when measuring the mass concentration of elemental carbon (or black carbon) in aerosols emitted by a medium-duty Diesel engine. Results indicate that the aethalometer response correlates well with the data from filter samples (R2 = 0.99), with a very slight positive interference at high levels of OC.

Jan 1, 2008

By K. Narayan Prabhu, W. D. Griffiths

"Heat transfer during the unidirectional solidification of a cast iron alloy against cast iron chills was investigated using an inverse modelling approach. Chills of thickness 100 mm and 10 mm were used, to simulate gravity die cruiting conditions and the use of chills in sand moulds. In both cases transient heat transfer, measured by the interfacial heat flux and heat transfer coeffieient; declined from initially high values in the first few seconds of solidification, to values about an order of magnitude lower which persisted for the remainder of the experiments. In the case of the thin chill it became saturated with heat until it was no longer in a position to extract further heat from ·the casting. These results were interpreted by studying the resistance to heat transfer from the casting offered by the ·casting-chill interface and the chill itself for example, the thermal resistance of the casting-chill interface can be influenced by the deformation of their respective surfaces and their subsequent relationship.IntroductionDie casting cast iron offers several advantages such as energy savings, higher mould yield, and better surface quality over the sand casting process1 • The process is· environmentally' friendly because of the elimination of the sand. However the design and construction of metallic moulds is expensive and a faulty die design may result in a defective casting: A simulation based process design of die castings would enable die designers and solidification modellings to try better designs of dies on the computer and arrive at a cost effective solution more quickly. This has numerous benefits for the die caster, as he would be able to produce sound castings with very short lead times.The success of a solidification model to predict accurately the thermal history and the location of hot, spots inside a solidifying casting depends to a large extent on the heat transfer data prescribed at the metal/mould interface. Many measurements of the heat transfer coeffident (or the heat flux) between a solidifying aluminum alloy and a chill have shown that the heat transfer coefficient is a function of most of the variables of the casting process2 - 8. However heat transfer studies during the solidification of ferrous alloys are rather limited. The high temperatures involved suggest that the contribution due to radiation heat transfer cannot be neglected."

Jan 1, 2000

By J. F. Colinet, W. R. Reed, J. D. Potts

Dust surveys were conducted at six underground coal mines to determine if deep-cutting practices expose face workers to higher levels of respirable dust. The surveyed mines were able to successfully mine deep cuts without significantly increasing the dust exposures of face workers. In general, all of the selected mines exercised good dust control practices by maintaining water sprays, scrubber airflows, proper curtain setback distances and providing sufficient airflow to the active faces. For exhausting face ventilation, field data indicate that scrubber airflow is the most important factor for controlling dust. Data collected for this study indicate that 20-mesh screens should be cleaned for every 12.2 m (40 ft) of advance, because 22% of the deep cuts surveyed for this study experienced a 20% to 35% decrease in scrubber airflow over the course of the cut. For blowing face ventilation, field data and past research indicate that dust control is aided by maintaining a proper curtain-to-scrubber airflow ratio of 1.0 (measured before scrubber activation), as well as a curtain setback distance that allows the miner operator to stand at the mouth of the curtain for the entire cut. Dust levels on the bolting faces did not appear to be affected by the longer cycles associated with deep-cut mining when good ventilation practices were used.

Jan 1, 2011

By E. J. Ripling, M. W. Toaz

Tensile tests were conducted on pure magnesium and on four commercial alloys over a variety of temperatures and strain rates. The high positive slope of the ductility vs testing temperature curves that is found over a short range of testing temperatures for these materaturerials was shown to result from the fact that the microstructure was not stable at these testing temperatures. Pure magnesium did not display a transition temperature, although its sub-room temperature ductility was low. This poor ductility resulted from a grain boundary weakness. The aluminum-bearing commercial magnesium alloys had a higher ductility than the pure magnesium. ness.Thealuminum-bearingcommercialThese alloys did exhibit a transition temperature and grain boundaries that were stronger than the grain material. Both pure magnesium and the commercial alloys began initiating cracks at strains equal to one half of their fracture strain. MAGNESIUM base alloys' enormous potential as structural materials lies in their high strength to weight ratios. At present, the high strength magnesium base alloys such as AZ-80, which will be discussed later, have about as high a tensile strength to specific gravity ratio as the highest strength wrought aluminum alloy, 75s-T6, and, of course, a much higher strength to weight ratio than structural steel. Further, since the magnesium base alloys develop their high strength to weight ratios with moderate strengths and extremely light weights, the ratio of load carrying capacity to the weight of many structures is relatively higher for the magnesium base alloys than their strength to weight ratios would indicate. This results because judicious increases in section size, such as increasing the depth of bending members or adding reinforcing ribs, can frequently increase the weight of a structure linearly while the strength and stiffness increase as the second or third power of the added weight. Strength and rigidity must be designed into lightweight structures by those techniques which establish multiaxial stress states. Consequently, strong, lightweight structures frequently also possess a greater propensity toward brittle failures. In order to insure against these catastrophic failures, an extra premium must be placed on ductility and toughness in light alloys. Current knowledge of the ductility and toughness behaviors—notched behaviors—of magnesium base alloys is limited.* Most of the magnesium base alloys * The state of present knowledge regarding the effect of testing temperature on mechanical properties has recently been summar-ized by Pritchard.' crystallize in the hexagonal system, so that they are expected to exhibit a tough and ductile to brittle transition temperature. Actually, a transition temperature behavior has been reported for commercially pure magnesium in the literature, but the characteristics of this transition temperatureh uggest that it may not be a transition in the usual meaning, but simply the onset of some thermal softening, a performance much like that which face-centered-cubic lead might exhibit slightly below room temperature. If transition temperatures do exist, such important questions as the manner in which they are affected by internal variables such as chemical composition and grain size, or the effect of external variables such as rate of straining or notch severity have never been investigated. The investigation reported upon herein was undertaken in order to define some of the mechanical behaviors of the magnesium base alloys better, to gain a better understanding of the influence of some of the above listed variables, and particularly to understand their effect on ductility and toughness better. Material and Procedure Material-—Pure magnesium and four commercial alloys were used in this investigation. The alloys were selected so that chemically they made up a series with approximately the same minor alloying

Jan 1, 1957