Abstract
The effects of mixing parameters on the microstructural homogeneity of green and sintered compacts composed of 80 wt-%Cu, 12 wt-%Pb, and 8 wt-%C powders has been studied by quantitative metallographic analysis of the distribution of the three phases. Mixing for up to 1 h in a cycloidal (Turbula) mixer and for up to 8 h in an intermittent (Sigma) mixer was investigated. In all cases, homogeneity increased with increasing mixing time, eventually reaching a steady state value. Optimum mixing times were found to be 30–60 min and 4–8 h for the cycloidal and spiral techniques respectively, although the copper distribution reached an optimal value after only 10 min with the former. Use of irregular rather that spheroidal lead powder. gave greater homogenisation in the green compacts pressed from spiral mixed powder, but these differences largely disappeared after sintering, which was generally found to increase homogenisation, as measured by coefficient of variation, by ∼20%. PM/0497
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