摘要:

AbstractThe binder phase of WC-Co cemented carbide is a Co-rich alloy in which tungsten and carbon are in solid solution. The binder phase is supersaturated with respect to tungsten even after slow cooling from the sintering temperature. In this study the binder phase contained 6% W in solid solution before heat-treatment at 650°C (923 K). Transmission electron microscopy on thin foils of binder phase showed that a finely dispersed. phase,α′, precipitated in the cubic binder phase. After long ageing times Co3W could be identified by X-ray diffraction methods. As no discontinuous ,‘cells’of Co3W and∊-Co could be observed, the following reaction is suggested.α-Co(W, C)→α-Co+α′→α-Co (C)+Co3W (needles)The precipitation ofα′was accompanied by an increase in hardness and a decrease in transverse rupture strength. The effects observed are consistent with those found during annealing of Co-rich cobalt-tungsten-carbon alloys (>85% Co).

ISSN:0032-5899    

DOI:10.1179/pom.1972.15.29.001

出版商:Taylor&Francis    

年代:1972

数据来源: Taylor

摘要:

AbstractA flotation method is described that enables the density and porosity of small specimens to be measured accurately by comparing their densities with those of reference specimens. The method uses the subtle, but accurately known, variation of the density of water with temperature to bring about neutral buoyancy of a specimen-float composite. Measurements can be made easily and quickly and the expressions derived for density and porosity are readily evaluated numerically.

ISSN:0032-5899    

DOI:10.1179/pom.1972.15.29.002

出版商:Taylor&Francis    

年代:1972

数据来源: Taylor

摘要:

AbstractMore than a hundred experiments have been performed to investigate the extrusion mechanism involved and the effect of process variables on the structure, substructure, and mechanical properties of the extrude when processing atomized aluminium powder of varying mesh size. It is demonstrated that extrusion pressure is largely independent of the final properties and that the ductility of the extrude may be controlled by the process variables. A mechanism that agrees with experimental observations is suggested to explain the extrusion mechanics. Transmission and scanning electron microscopy results also support the theses presented.

ISSN:0032-5899    

DOI:10.1179/pom.1972.15.29.003

出版商:Taylor&Francis    

年代:1972

数据来源: Taylor

摘要:

AbstractThe structure of porous nickel plaques produced by the following routes has been examined using scanning electron microscopy: (a) pressure-less sintering of nickel powder; (b) slurry sintering of powder; (c) roll-compaction and sintering of powder; (d) pyrolysis of cloth impregnated with nickel chloride. The observations show that measurements of pore-size distribution with a mercury porosimeter can be misleading, and also reveal the existence of fine closed porosity in plaques made from impregnated cloth. The relation of the observed porosity characteristics and inter-particle bond diameters to the mechanical and electrical properties of the plaques is discussed.

ISSN:0032-5899    

DOI:10.1179/pom.1972.15.29.004

出版商:Taylor&Francis    

年代:1972

数据来源: Taylor

摘要:

AbstractA study of the sintering behaviour of iron compacts containing additions of tin up to 1 wt.-% has been made. A tensile strength of 234 MN/m2(34 x 103lbf/in2) has been achieved with an optimum tin addition of 0·5 wt.-%, sintering being carried out for 10 min at 1100°C (1373 K) in a reactive halide atmosphere. Combination of the two‘activating’techniques (addition of tin and sintering in a reactive atmosphere) permits current properties to be attained at considerably lower sintering temperatures or sintered densities, and is much more effective than when they are applied individually. A tensile strength of 165·3 MN/m2(24 x 103lbf/in2), achieved by sintering at 1200°C (1473 K) for 10 min with an addition of 0·5 wt.-% tin can be obtained by reactive-sintering the same composition at 900°C (1173 K) for 10 min. Alternatively, the density of the part can be reduced from 6·7 to 6·2 g/cm3with no loss of strength or elongation. Tin in excess of 0·5 wt.-% causes deterioration in properties under the sintering conditions studied and a reason for this is cited. The improvements in properties are lost also if admixed lubricant is used in the compactionprocess.

ISSN:0032-5899    

DOI:10.1179/pom.1972.15.29.005

出版商:Taylor&Francis    

年代:1972

数据来源: Taylor

摘要:

AbstractReduced iron, copper-base, and refractory metal powders have dominated the raw-material field during the rapid growth of the PM industry in the last 30 years. Emphasis has been on the economic mass production of structural parts, rather than on properties. New material concepts have brought about the need for new and improved powders possessing enhanced properties and performance reliability, i.e. atomized powders. Modern atomizing techniques and parameters are reviewed in terms of their economics and influence on powder properties, chemistry, ultimate structural control, property reliability, and alloy and process flexibility, especially with materials difficult to fabricate.

ISSN:0032-5899    

DOI:10.1179/pom.1972.15.29.006

出版商:Taylor&Francis    

年代:1972

数据来源: Taylor

ISSN:0032-5899    

DOI:10.1179/pom.1972.15.29.007

出版商:Taylor&Francis    

年代:1972

数据来源: Taylor