The improved mechanical properties of Al matrix composites reinforced with oriented β-Si3N4 whisker

The beta-Si3N4 whiskers (beta-Si(3)N(4)w) reinforced Al matrix composites were first fabricated by hot pressing, then treated through hot extrusion. The microstructure characterization demonstrated the preferred orientations of both beta-Si(3)N(4)w and Al grains in the as-extruded composites. It indicated that beta-Si(3)N(4)w were aligned along the extrusion direction and Al grains exhibited a distinct <111>(Al) texture. The interface between beta-Si(3)N(4)w and Al was in a good bonding status without voids and reaction products. Effects of extrusion process on the mechanical properties of composites were also investigated. The results indicated the extrusion process had a prominent strengthening effect on the mechanical properties of composites. The maximum yield strength and ultimate tensile strength of composites reached up to 170 and 289 MPa, respectively, accompanied by a 12.3% elongation at fracture when the whisker fraction was 15 vol.%. This improvement was collectively attributed to the densification of composites, the strong interface, and the preferred orientation inside composites. The yield strength of the composites reinforced with 5 vol.% beta-Si(3)N(4)w corresponded well with the theoretical value from different strengthening mechanisms. (C) 2019 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.