Effects of matrix powder size and heat treatment after forming on the strength of SiC whisker reinforced aluminum composites produced by combined extrusion.

For each matrix powder size, the tensile strength of composite increased proportionally with increasing volume fraction of the whisker, Vf, up to a critical value, (Vf)c, beyond which the strength was holded. (Vf)c increased with decreasing powder size. Thus, the composite produced with finer matrix powder was effectively strengthened by the whisker up to higher Vf. The amount of whisker per unit surface area of matrix powder calculated for each size of powder at (Vf)c coincided approximately with each other. The specific amount of whisker was considered to be a limitation to effectively reinforce the matrix. As for the effect of heat treatment on the strength of composite, it was 20% increased by heating at 913 K for about 30ks. On the other hand, the prolonged heat treatment reduced the strength by causing remarkable reaction between the whisker and the matrix.