Showing papers on "Powder metallurgy published in 1981"

Aluminium powder metallurgy technology for high-strength applications

Abstract: A literature survey of aluminium powder metallurgy (PM) for high-strength applications was undertaken. Improvements in aluminium—base alloys made via ingot metallurgy (IM) are reaching the point of diminishing returns. PM offers an alternative technology, capable of producing alloys having improved fatigue, corrosion, and stress-corrosion resistance, as well as improved strength and toughness at room or elevated temperatures. The steps involved in powder metallurgy: powder manufacture, powder processing, de-gassing, and consolidation, are described. The merits and deficiencies of the various processes for each step are compared. The key to successful application of Al powder metallurgy alloys appears to be the de-gassing and consolidation of the powder. The properties of several new PM alloys are compared, with particular emphasis on highstrength, corrosion-resistant alloys and alloys developed for use at elevated temperatures.

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.

New Approaches to Alloy Development in the Al-Li System

Abstract: This paper describes the approach and results of recent work in our laboratories on identifying and solving the ductility problems which have plagued Al-Li alloys. In addition, specific property goals for developing new Al-Li alloys have been established. These include a) a 30% increase in modulus:density ratio, compared to 7075-T76, without significant loss in other properties, and b) a 20% increase in modulus:density ratio and a 20% increase in strength:density ratio compared to 7075-T76, without significant loss in other properties. Two approaches are being pursued, one using conventional ingot metallurgy (I/M) and the other using rapid solidification of fine particulate plus powder metallurgy (P/M) consolidation. The rapid solidification approach is designed to reduce or eliminate segregation effects, reduce the grain size, extend solid solubility of additional elements, and refine the dispersoid particle size. In some cases, we have made a comparison of the structure and properties of similar alloys fabricated by the two methods.

Fabrication of multifilamentary Nb-Al by a powder metallurgy process

Abstract: Fabrication of multifilamentary Nb-Al superconducting wires with high overall critical current densities at high fields is discussed. Powder metallurgy processed materials have been made with low reaction temperatures and with J c > 104A/cm2at 14 T. The effects of variations of Nb and Al powder size, composition, reduction ratio, reaction temperature, and reaction time on J c vs appiied field are presented. All the Nb-Al materials show good strain tolerance at high J c and high field. The results also show that scaleup is promising.

Cold forced sintered powder metal annular bearing ring blanks

Abstract: A method and material for the manufacture of improved bearing elements such as annular inner and outer bearing ring blanks for ball, roller and needle bearing assemblies comprising the steps of mixing a powder consisting substantially of iron with ferro-alloy powders of substantially smaller size, each ferro-alloy containing at least 80% iron and the balance being an alloying element, together with graphite powder and a lubricant, compacting the resulting mixture to form a preform, pre-sintering the preform, and then coating the sintered preform with a stop-off and lubricant The preform is subjected to a plastic deformation of at least 50% in a cold (room temperature) forging operation to produce an article which is at least 98% dense and has approximately the shape of the finished article This cold forged shape is resintered and annealed, after which the annealed and resintered shape is roll formed into substantially final dimensions The article can be followed by a suitable heat treatment for hardening the shape

Atomization of Specialty Alloy Powders

Abstract: This article reviews powder making methods involving the atomization of liquid metal, with particular reference to specialty alloys. The methods are classified as commercial, pilot-scale, and laboratory-scale. Powder characteristics and properties are considered in relation to process parameters; where available, mechanisms of the break-up of the liquid metal stream or sheet are analyzed.

Powder Metallurgical Innovations for Improved Hot-Section Alloys in Aeroengine Applications

Abstract: Throughout the past decade a number of new powder metallurgy processes have appeared which offer con siderable promise for superior aeroengine combustor, blade, and disc alloys. Furthermore, several features of these processes can be exploited for improved material utilization such that total manufacturing costs are contained to combat steep increases in basic alloying element prices. The processes include gas atomization of superalloy powder for critical rotating parts, rotating electrode atomization for titanium powder in similar components, controlled thermomechanical processing of attrited powders to produce oxide dispersion strengthened superalloy sheet and airfoil parts, and finally plasma-sprayed gas-atomized powder for advanced hot-section overlay and thermal barrier coatings. Considerable alloy and process development work has already been undertaken on all these systems by aeroengine material suppliers and advantages accruing in terms of superior properties and/or lower processing costs ...

Effects of fine porosity on the fatigue behavior of a powder metallurgy superalloy

Abstract: Hot-isostatically-pressed powder-metallurgy Astroloy was obtained which contained 1.4 pct, fine porosity at the grain boundaries produced by argon entering the powder container during pressing. The pores averaged about 2μ,m diam and 20 μ m spacing. This material was tested at 650 °C in fatigue, creep-fatigue, tension, and stress-rupture and the results compared with previous data on sound Astroloy. The pores influenced fatigue crack initiation and produced a more intergranular mode of propagation. However, fatigue life was not drastically reduced. A large 25 μm pore in one specimen resulting from a hollow particle did reduce life by 60 pct, however. Fatigue behavior of the porous material showed typical correlation with tensile behavior. The plastic strain range-life relation was reduced proportionately with the reduction in tensile ductility, but the elastic strain range-life relation was little changed reflecting the small reduction in strength divided by modulus for the porous material.

Properties of High-Speed Steels Produced by Powder Metallurgy

Abstract: The ‘KHA process’ for producing PM high-speed steels using gas-atomizing equipment and the hot isostatic press has been developed by Kobe Steel Ltd. Measurement of the secondary dendrite arm spacing of gas-atomized powders indicated that the relation between the dendrite arm spacing S II (μm) and the powder particle diameter d (m) was described by S II= K□d where K is a constant. To establish suitable hot isostatic pressing (HIP) conditions with high productivity, density and bending strength were studied in relation to various HIP conditions. It was found that, for example, the combination of 1373K, 40MPa, 30 min was sufficient to obtain full density, but that 1473K, 40MPa, 30min was required to obtain the maximum bending strength. By studying various properties of KHA high-speed steels, it was found that they were superior to the conventional steels for toughness, grindability, and hot workability. Tools such as drills, end mills, hobs, etc. produced from KHA materials exhibited better cutting p...

High-temperature electrically conductive ceramic composite and method for making same

Abstract: The present invention relates to a metal-oxide ceramic composition useful in induction heating applications for treating uranium and uranium alloys The ceramic composition is electrically conductive at room temperature and is nonreactive with molten uranium The composition is prepared from a particulate admixture of 20 to 50 vol % niobium and zirconium oxide which may be stabilized with an addition of a further oxide such as magnesium oxide, calcium oxide, or yttria The composition is prepared by blending the powders, pressing or casting the blend into the desired product configuration, and then sintering the casting or compact in an inert atmosphere In the casting operation, calcium aluminate is preferably added to the admixture in place of a like quantity of zirconia for providing a cement to help maintain the integrity of the sintered product

Sintering furnace for powder metallurgy

Abstract: The present invention relates to a sintering furnace for powder metallurgy of cemented carbides, cermets and ceramics, which comprises a main furnace body, a heating chamber provided in the main body, a table having a moving means for carrying a workpiece in or out of the heating chamber and a means for cooling the interior of the furnace with a heat exchanger fitted to the exterior of the main furnace body, and a method for the sintering and heat treatment of cemented carbides in the sintering furnace as claimed in claim 1, which comprises sintering cemented carbides and cooling rapidly at a cooling rate of at least 30° C./min from the sintering temperature being at least a temperature at which a liquid phase appears to at most 1000° C. by the use of an inert gas as a coolant.

Steel-hard carbide macrostructured tools, compositions and methods of forming

Abstract: 57 Composition of matter composed of 30 to 80 weight per cent of a carbide material having a particle size greater than 400 mesh, and 20 to 70 weight per cent of a metallic matrix material, the carbide material which may be a cemented composite (30), being embedded in and bonded to said metallic matrix material (25) by powder metallurgical techniques of compaction and high temperature and high pressure diffusion bonding; and tools having a cemented carbide wear or cutting element (30), these tools also being formed by powder metallurgy techniques.

High-Temperature Alloys from Powders

Abstract: (1981) High-Temperature Alloys from Powders Powder Metallurgy: Vol 24, No 1, pp 32-40

Fe--Cr--Co Magnets by powder metallurgy processing

Abstract: Fe--Cr--Co alloys have found application in the manufacture of permanent magnets on account of magnetic properties such as, high coercive force, remanent magnetization, and energy product. A method is disclosed for producing magnetic articles comprising Fe, Cr, and Co from powders comprising elemental or pre-alloyed particles. A powder is mixed with an essentially noncarbonizing organic binder, compressed, heated to remove binder, sintered, and aged. Heating results in essentially complete removal of binder prior to sintering. Magnetic bodies produced according to the disclosed method typically comprise less than 1 weight percent of undesirable nonmagnetic phases and have a maximum energy product of at least 1 million gauss oersted.

Shape-memory alloy based on copper, zinc and aluminum and process for preparing it

Abstract: A fine-grained shape-memory alloy of the Cu/Zn/Al type, prepared by powder metallurgy, exhibiting the beta-high temperature phase, having dispersed in the matrix dispersoids in the form of Y2 O3 and or TiO2 particles which limit grain growth, and a process for preparing this alloy using mechanical alloying.

Mechanical Properties and Microstructure of Argon Atomized Aluminum-Lithium Powder Metallurgy Alloys

Abstract: Aluminum-lithium and aluminum-copper-lithium alloy powders were prepared by argon gas atomization. The powders were consolidated by hot pressing and extruded into flat bar. Tensile and impact properties were determined on the extrusions. Transmission electron microscopy was used to examine the extruded microstructures while scanning microscopy was used for the examination of fracture surfaces. The aluminum-lithium alloys showed higher moduli, lower densities, and reduced toughness and elongation compared to conventional aluminum alloys. The loss of toughness was particularly pronounced above 3 pct Li.

Further development of powder processed multifilamentary superconductors

Abstract: Progress in the development of powder metallurgy (P/M) processing of multifilamentary superconductors is discussed for 4 approaches: 1) Cu-Nb-Sn wires were fabricated using internal microscopic diffusion of Sn produced by Sn powder or prealloyed (SnCu) powder; 2) Cu-NbTa-Sn was produced with prealloyed Nb 4 wt % Ta and Nb 7 wt % Ta powders and external Sn diffusion; 3) hot processing was demonstrated using sintering or hydrostatic extrusions with Cu and Nb, or Cu and NbTa powders with or without Al as a function of particle size; and 4) Nb-Al material was develop ed with a (P/M) process. All show high overall critical currents at high field, good strain tolerance, and promise for scaleup processing.

Method of producing a memory alloy

Abstract: Cu/Al and Cu/Al/Ni memory alloys having improved mechanical properties are prepared by powder metallurgy from mixtures of pre-alloyed and/or pre-mixed powder ingredients. The mixture of powder ingredients is subjected successively to isostatic pressing, sintering in an inert atmospheric and subsequent multi-step hot working with intermediate annealing which serves to homogenize. Final annealing is carried out in the β-phase solid solution temperature range and the annealed article is quenched in water.

Oxidation and hot corrosion of coated and bare oxide dispersion strengthened superalloy MA-755E

Abstract: Cyclic hot corrosion and oxidation testing of an experimental oxide dispersion strengthened (ODS) superalloy MA-755E were conducted in a hot gas stream at Mach 0.3. The response of the ODS alloy, bare or with protective coatings, was similar to that of a conventional cast alloy, IN-792, in hot corrosion at 900°C. However, during oxidation at 1100 and 1150°C the ODS alloy differed from the cast alloy by developing a greater amount of subsurface porosity. Compared with a diffused aluminide coating, an electron beam vapor deposited NiCrAlY coating offered superior oxidation protection and decreased porosity formation. In additional testing, the tendency to form porosity was associated with the large grains of recrystallized powder metallurgy alloys but was independent of the presence of an oxide dispersion.

Temperature‐sensitive Nd‐Co compounds produced by powder metallurgy

Abstract: A powder metallurgical process has been developed to prepare Nd‐Co compounds which show the spin reorientation (SR) phenomenon. In this process, single crystals of the compounds in fine powder form are aligned in a magnetic field at a temperature more than 50 °C above the SR temperature. Complete uniformity is especially important in the chemical composition of the powders. As a result of studying many elements as substituents in NdCo5, an Nd (Co1−x−yAlxFey)5 system has been developed. The SR temperature of this compound system can be extended beyond 150 °C by controlling composition of the compound as may be required for different applications.

Sintered powder metal friction material

Abstract: An iron-base, sintered powder metal friction material suitable for railroad braking is disclosed. The friction material comprises, by volume, 10-70% carbon; 0-2.5% sulfur; 0-10% alumina; 1-45% of a metal powder additive selected from the group consisting of copper, manganese, ferrochrome, chrome carbide compounds and mixtures thereof; and the balance iron. In preferred embodiments, the powder metal additives are 11-25% copper, or 9-15% manganese, or 5-20% ferrochrome.

Articles produced from iron powder compacts containing hypereutectic copper phosphide powder

Abstract: In the preferred embodiment, a method is presented for forming an iron-base article by powder metallurgy, which includes compacting a powder mixture comprising a major portion of iron particles and between about 2 to about 5 weight percent of a powder consisting of hypereutectic tricopper phosphide Cu 3 P compound. The compact is sintered at a temperature between about 970° C. to about 1100° C., whereupon the copper phosphide forms a liquid that flows and wets the iron particle surfaces. During sintering, phosphorus from the copper phosphide diffuses into the iron particles and resulting copper-enriched liquid forms a film coating pore surfaces in the compact. The sintered article displays an improved combination of ductility and strength, particularly in view of the relatively low sintering temperature.

Memory alloys based on copper or nickel solid solution alloys having oxide inclusions

Abstract: Fine grained copper-based or nickel-based memory alloys having a matrix of β-high temperature phase with metal oxide particles dispersed in the matrix which act to retard grain growth have improved mechanical characteristics such as elongation, toughness and workability, compared to cast and worked alloys. These alloys are produced by powder metallurgy.