Powder Processing and Tensile Properties of SiC Whisker Reinforced Al Composites

Abstract

SiC whisker reinforced aluminum composites with whisker volume fraction ranging from 0 to 20% were fabricated by a powder metallurgy method, that is, a combination of hot pressing and hot extrusion. The relation between the microstructure and the tensile properties of the composites was discussed.
The main results obtained were as follows;
(1) The SiC/Al composites fabricated by the appropriate combination of hot pressing and hot extrusion had theoretical density. The deviation of whiskers from the extruded direction was within about ±4 degree.
(2) The tensile strength of SiC/Al composites increased with increasing the volume fraction of SiC whisker; for example, 20 v% SiC/Al composite had the tensile strength of 387MPa. The experimental tensile strength exceeded the predicted one. The possible reason was that the real value of shear yield stress of the matrix was larger than our estimate.
(3) The tensile fracture behavior of SiC/Al composites was as follows. At first the interfacial voids were formed at whiskers ends, then grew gradually and finally joined each other along the shear direction.
(4) The tensile strength of SiC/Al composites at elevated temperatures decreased with increasing temperature, but the tensile strength of 20 v% SiC/Al composite at 723K was two times as strong as that of pure aluminum.