Showing papers on "Alloy published in 1981"

Structure and properties of engineering alloys

Abstract: 1 Iron-Carbon Alloys I 2 Iron-Carbon Alloys II 3 Carbon Steels 4 Alloy Steels 5 Aluminum Alloys 6 Copper Alloys 7 Stainless Steels 8 Cast Irons 9 Tool Steels 10 Titanium Alloys 11 Nickel and Cobalt Alloys 12 Magnesium and Zinc Alloys 13 Refractory Alloys 14 Surface Hardening and Modification of Metals

Preparation and properties of cast aluminium-ceramic particle composites

Abstract: A casting technique for preparing aluminium-alumina, aluminium-illite and aluminium-silicon carbide particle composites has been developed. The method essentially consists of stirring uncoated but suitably heat-treated ceramic particles of sizes varying from 10 to 200 μm in molten aluminium alloys (above their liquidus temperature) using the vortex method of dispersion of particles, followed by casting of the composite melts. Recoveries and microscopic distribution of variously pretreated ceramic particles in the castings have been reported. Mechanical properties and wear of these composites have been investigated. Ultimate tensile strength (UTS) and hardness of aluminium increased from 75.50 MN m−2 and 27 Brinell hardness number (BHN) to 93.15 MN m−2 and 37 BHN respectively due to additions of 3 wt % alumina particles of 100 μm size. As a contrast, the tensile strength of aluminium-11.8 wt % Si alloy decreased from 156.89 MN m−2 to 122.57 MN m−2 due to the addition of 3 wt % alumina particles of the same size. Adhesive wear rates of aluminium, aluminium-11.8 wt % Si and aluminium-16 wt % Si alloys decreased from 3.62×10−8, 1.75×10−8 and 1.59×10−8 cm3 cm−1 to 2.0×10−8, 0.87×10−8 and 0.70×10−8 cm3 cm−1, respectively, due to the additions of 3 wt % alumina particles.

Mechanism of the Electrodeposition of Zinc Alloys Containing a Small Amount of Cobalt

Abstract: Corrosion resistant Zn‐Co alloys were electrodeposited on the steel sheet cathode from an acid galvanizing bath containing a small amount of cobalt sulfate. Under most of the plating conditions studied, the anomalous codeposition and, hence, the preferential deposition of electrochemically less noble Zn occurred. The electrodeposition process of the alloy including the Zn hydroxide formation resulting from the rise in pH in the vicinity of the cathode was estimated by electrochemical and spectroscopic studies.

Fabrication and characterization of SiC-AIN alloys

Abstract: SiC-AIN alloys were prepared by the carbothermal reduction of silica and alumina, derived from an intimate mixture of silica, aluminium chloride and starch. The resulting single-phase SiC-AIN powder was hot-pressed without additives to a high density. The dense bodies had a fine-grained uniform microstructure. The Young's elastic modulus, microhardness, fracture toughness, thermal expansion and thermal conductivity were measured as functions of composition. The creep behaviour of the SiC-AIN alloy was compared with that of silicon carbide.

Infiltrated powdered metal composite article.

Abstract: Precision molded articles, such as die cavities, pertaining to the field of powder metallurgy, and having high hardness and impact resistance, are made by combining granules of refractory and granules of a first metal or alloy which has a homogeneous crystalline appearance at a temperature below its melting point and a lower Rockwell Hardness than the refractory, mixing the granules with organic binder, molding the granule-binder mixture into a green molded preform, thermally degrading and removing the binder to form a skeletal preform, and infiltrating the preform with a second metal or alloy which will wet the first metal or alloy and has a lower Rockwell Hardness than the first metal or alloy, thereby forming a molded article having refractory granules fully enveloped within a single skeleton of the first metal or alloy, the refractory granules and skeleton being surrounded by layers or matrices of softer metals.

Structu re-property relationships in commercial low-alloy bainitic-austenitic steel with high strength, ductility, and toughness

Abstract: A commercial low-alloy steel exhibiting combinations of mechanical properties superior to those of many other highly alloyed steels has been designed. The good properties are achieved by a carbide-free bainitic–austenitic structure, which can be produced by isothermal heat treatment of high-carbon silicon-alloyed steels in the upper bainite temperature range. Structure–property relationships are evaluated in order to find the optimum combination of heat treatment and alloy content. The effective grain size, the austenite volume fraction, and the austenite morphology are important factors controlling the properties. The mechanical stability of the austenite is of little importance.

Influence of oxygen-rich inclusions on the ??? phase transformation in high-strength low-alloy (HSLA) steel weld metals

Abstract: Reducing the oxygen content of two submerged-arc, high-strength, low-alloy (HSLA) steel weld metals has been shown to depress γ→α transformation temperatures and produce a marked change in the resultant microstructures. In weld metal of composition 0.12wt% C, 1.35wt% Mn, 0.29 wt% Si, 0.03 wt% Nb reducing the oxygen content from about 300 ppm to about 60 ppm decreased the transformation initiation temperature by about 30° C and changed the microstructure from acicular ferrite to parallel lath ferrite. In weld metal of composition 0.1 wt% C, 0.8 wt% Mn, 0.1 wt% Si, 0.01 wt% Nb reducing the oxygen content from about 600 ppm to about 300 ppm decreased the transformation initiation temperature by approximately 20° C and favoured the development of ferrite side-plates and acicular ferrite at the expense of the polygonal ferrite microstructure. In both weld metals the depressed transformation temperature is thought to be due to the larger γ-phase grain size developed when the volume fraction of small de-oxidation products is reduced. The marked microstructural change from fine-grained acicular ferrite to parallel lath ferrite which occurred when virtually all the de-oxidation products were removed suggests that these small de-oxidation products may also be of fundamental importance to the nucleation of acicular ferrite.

Electrodes for Alkaline Water Electrolysis

Abstract: Electrodes for alkaline water electrolysis have been made by applying high specific surface area coatings of nickel or nickel‐iron alloy to steel or nickel substrates. The coatings are applied as polysilicate‐based paints containing particles of the desired metals. The coating is sintered into a porous structure which is bonded firmly to the substrate. The present electrode preparation method has been used to coat a variety of substrate forms, such as flat plates or wire screens, and is compatible with commercial alkaline electrolysis equipment. The resulting electrodes were found to be particularly effective as anodes for oxygen evolution. The efficiency of the electrodes was greatly influenced by coating microstructure. This microstructure, in turn, could be controlled by adjusting the sintering conditions. Electrochemical operating characteristics of the electrodes in at 80°C were determined. Comparable oxygen evolution efficiencies were obtained with coatings made from nickel powders, nickel flake, and nickel‐iron alloy powder.

The advantages of titanium alloy over stainless steel plates for the internal fixation of fractures. An experimental study in dogs

Abstract: An experimental study is reported of fracture healing in the femora of 36 Beagle dogs, comparing the results of using stainless steel plates with those of using less rigid titanium alloy plates. The alloy plates led to the appearance of a small amount of periosteal callus without any histological evidence of fracture instability, thus allowing the radiological assessment of fracture union. This also produced less bone loss during the remodelling phase. Radiological measurements 24 weeks after osteotomy showed cortical thickness to be reduced by six per cent under titanium alloy and by 19 per cent under stainless steel, while histological measurements showed a total bone loss of 3.7 per cent under titanium alloy and of 11 per cent under stainless steel plates. Removal of the titanium alloy plates after eight weeks followed by a recovery period of 16 weeks produced an increase of cortical thickness of 69 per cent and a gain in total bone mass of 30 per cent. Titanium alloy plates also produced less soft-tissue reaction than stainless steel plates. It is concluded that this alloy is a promising material for internal fixation devices.

Amorphous yttrium-iron alloys. I. Magnetic properties

Abstract: The magnetic properties of amorphous yttrium-iron alloys Y1-xFex have been studied over a wide concentration range 0.32

The UPAL process: a direct method of preparing cast aluminium alloy-graphite particle composites

Abstract: A direct method of preparing cast aluminium alloy-graphite particle composites using uncoated graphite particles is reported. The method consists of introducing and dispersing uncoated but suitably pretreated graphite particles in aluminium alloy melts, and casting the resulting composite melts in suitable permanent moulds. The optical pretreatment required for the dispersion of the uncoated graphite particles in aluminium alloy melts consists of heating the graphite particles to 400° C in air for 1 h just prior to their dispersion in the melts. The effects of alloying elements such as Si, Cu and Mg on the dispersability of pretreated graphite in molten aluminium have also been reported. It was found that additions of about 0.5% Mg or 5% Si significantly improve the dispersability of graphite particles in aluminium alloy melts as indicated by the high recoveries of graphite in the castings of these composites. It was also possible to disperse upto 3% graphite in LM 13 alloy melts and retain the graphite particles in a well distributed fashion in the castings using the pre-heat-treated graphite particles. The observations in this study have been related to the information presently available on wetting between graphite and molten aluminium in the presence of different elements and our own thermogravimetric analysis studies on graphite particles. Physical and mechanical properties of LM 13-3% graphite composite made using pre-heat-treated graphite powder, were found to be adequate for many applications, including pistons which have been successfully used in internal combustion engines.

Phase Diagram of Amorphous and Crystallized Fe-B Alloy System

Abstract: A study of the structure change with temperature for Fe100-xBx alloys (x=2~33 at.%B) fabricated by a rapid quenching technique has been carried out by measuring magnetization, electrical resistivity and thermal expansion and also by structural analysis by X-ray diffraction. The amorphous alloys with 11x13 at.%B transform into α-Fe(B) around 300°C which has a smaller lattice constant than that of α-Fe. Then α-Fe(B) decomposes into two stable α-Fe and Fe2B at about 450°C. For the amorphous alloys with 14x25 at.%B, the amorphous phase transforms into both α-Fe and tetragonal Fe3B compound at about 400°C. With further heating, an orthorhombic Fe3B compound can be observed clearly in addition to these 2 phases for 17x25 at.%B. For temperatures beyond 600~700°C, they transform to the equilibrium phases of α-Fe and Fe2B compound.

Metastable Au-Si alloy formation induced by ion-beam interface mixing

Abstract: An amorphous Au-Si alloy with composition Au-28·5 at. % Si (Au5Si2) has been formed by inplanting energetic Xe, Ar or Ne ions through a thin layer of Au deposited on a Si substrate. The ion-induced amorphous Au-Si alloy is uniform in composition and in thickness as indicated by 4He+ backscattering measurement. The Au-Si alloys so obtained were studied by resistivity measurements and by transmission electron microscopy and diffraction. Two distinct stages of phase transformation are observed as revealed by a sudden change of resistivity with increasing annealing temperature. In the first stage, a transformation from amorphous to a metastable crystalline Au5Si2 phase occurs in a narrow temperature range around 100°C. The second stage, which appears broader near 180°C, involves the transformation to the equilibrium two-phase state of Au and Si. The kinetics of the amorphous to metastable crystalline transformation has been determined by isothermal annealing over the temperature interval 85-101°C. An...

Glass formation and crystallization in highly undercooled Te-Cu alloys

Abstract: The large undercoolings required for glass formation have been achieved by the slow cooling (10-20°C/min) of liquid Te-Cu alloys in the form of a fine droplet emulsion. Within the region of glass formation, between 19 and 39 at.% Cu, DTA measurements indicate that the glass ( T g ) and crystallization ( T c ) temperatures during heating exhibit a broad maximum at the eutectic. During slow cooling of Te-rich alloy droplets, the maximum undercooling for nucleation increases from 213°C for pure Te to 264°C for Te-12.5 at.% Cu. An enhanced depression of the nucleation ( T n ) temperature compared with the change of the liquidus develops in Te-rich alloys upon approaching the glass forming composition range and can be a useful feature in assessing the glass forming tendency. Thermal cycling experiments indicate that even at an undercooling of 181°C crystallization in an eutectic Te-29 at.% Cu alloy is limited by an inadequate nucleation rate in clean droplet samples. For a eutectic alloy, at undercoolings in excess of 200°C crystal nucleation does develop in the droplet samples, but complete crystallization is hindered by a rapidly rising liquid viscosity with increased undercooling.

Hard magnetic alloys of a transition metal and lanthanide

Abstract: A hard magnetic alloy comprises iron, boron, lanthanum, and a lanthanide is prepared by heating the corresponding amorphous alloy to a temperature from about 850 to 1200 K. in an inert atmosphere until a polycrystalline multiphase alloy with an average grain size not exceeding 400 A is formed.

Growth of Alloy Carbide Particles in Austenite

Abstract: The growth of Cr7C3, Mo6C, VC and NbC carbides in austenite was examined in the ranges of temperature from 1173 to 1473K, and time from 10 to 200h. The growth rate decreases in the order Cr7C3, Mo6C, VC and NbC. It was found that the carbides grew in two stages. The growth of carbides occurs initially by taking the solute from the matrix until an equilibrium is attained, and later by Ostwald ripening. For the carbides with lower growth rates, higher heating temperatures and/or longer times were required to reach the equilibrium. The rate equation in the stage of Ostwald ripening of alloy carbides in ternary Fe-GM alloys was derived in the case in which the lattice diffusion of M atoms controlled the growth rate. The equation well described the growth rates of the alloy carbides in the latter stage. (Received June 1, 1981)

Casting with Zinc Alloys

Abstract: Zinc-based alloys have been used for pressure die-casting applications for decades because of their excellent mechanical properties and economic advantages as compared to other pressure die-casting alloys, such as copper-, magnesium-, and aluminum-based alloys However, recently there has been a growing interest in the use of zinc-based alloys as a general purpose foundry alloy In this article the metallurgy of the zinc-aluminum based family of alloys is discussed; the pressure die casting and gravity casting zinc alloys are fully described in terms of chemical composition and mechanical properties Casting with zinc alloys can offer material, processing, and economic advantages; these are covered and examples of applications are given Though the superiority of zinc-based alloys for pressure die-casting applications vis-a-vis other die casting alloys has always been realized, this has not been the case for the foundry (gravity cast) alloys It is shown that the zinc-based alloys are viable engineering materials; that they possess distinct processing and economic advantages, and exhibit mechanical properties which are competitive with other traditional casting alloys — both ferrous and nonferrous

Long-term ageing characteristics of some commercial nickel-chromium-molybdenum alloys

Abstract: The long-term ageing characteristics of some commercial Ni-Mo-Cr alloys (the high-temperature HASTELLOY alloy S and the corrosion resistant HASTELLOY alloys C-4 and C-276) at 810 K were investigated. It was found that the three alloys undergo the following long-range ordering reaction: disordered f c c lattice → ordered orthorhombic, Pt2Mo-type superlattice. Ordering was found to cause considerable strengthening without severe loss of tensile elongation. Deformation in the ordered state occurred predominantly by twinning. The corrosion rates of alloys C-4 and C-276 in boiling sulphuric-ferric sulphate solution did not seem to be greatly affected by the long-range ordering reaction. In addition to ordering, the three alloys were also found to undergo grain boundary reactions. The resulting phase in alloys S and C-4 assumed a dispersed morphology and was identified as carbide, probably of the Type M12C. In alloy C-276, however, which contains higher amounts of iron and tungsten, the boundary precipitate was in the form of a continuous layer consisting of M12C and Mu-phase. This could account for the reduced tensile elongation of alloy C-276 relative to alloys S and C-4 and also to its high corrosion rate.