Enhanced tensile properties of Al matrix composites reinforced with β-Si3N4 whiskers

Al matrix composites reinforced with β-Si3N4 whiskers (β-Si3N4w) were fabricated by hot pressing method. The microstructures showed that the whiskers were uniformly dispersed in the matrix and the Al/β-Si3N4 interface was well bonded without interface reaction. Effects of β-Si3N4w content and sintering parameters on the densification and tensile behavior of composites were investigated. The results indicated that β-Si3N4w could both enhance the ultimate tensile strength (UTS) and maintain the ductility of Al matrix when the whisker content was 5 vol%, corresponding to an elongation at break and an UTS of 21.2% and 239 MPa, respectively. However, higher whisker content could improve UTS of composites to the maximum value of 312 MPa, which was 158 MPa higher than pure Al, while reducing elongation of composites. The fracture mechanism changed from ductile fracture to a combination of both ductile and brittle fracture mechanism with the increase of whisker content.