Brass-matrix silicon carbide whisker composites prepared by powder metallurgy

Brass (Cu-18Zn)-matrix and copper-matrix composites containing 0-50 vol% si licon carbide whiskers were fabricated by powder metallurgy using both the admixture method and the coated filler method, such that the fabrication of the copper-matrix composites did not involve a liquid phase whereas that o f the brass-matrix composites did during the sintering process. The coated filler method gave composites with lower porosity, greater hardness, higher compressive yield strength, lower coefficient of thermal expansion (CTE), higher thermal conductivity and lower electrical resistivity than the admix ture method, though the differences were much larger for copper-matrix comp osites than brass-matrix composites due to the liquid phase present during the fabrication of the brass-matrix composites. The mechanical properties o f the brass-matrix composites were similar to those of the copper-matrix co mposites (also made by the coated filler method) at >35 vol% SIG, but were superior to those of the copper-matrix composites at <35 vol% SIG. The CTE was lower for brass-matrix composites than copper-matrix composites at >35 vol% SIG. The thermal conductivity was lower and the electrical resistivity was higher in brass-matrix composites than copper-matrix composites at <50 vol% SiC. (C) 1999 Kluwer Academic Publishers.