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

The β-Si3N4 whiskers (β-Si3N4w) reinforced A1 matrix com posites were first fabricated by hot pressing, then treated through hot extrusion. The microstructure characterization dem onstrated the preferred orientations of both β-Si3N4w and A1 grains in the as-extruded composites. It indicated th at β-Si3N4w were aligned along the extrusion direction and A1 grains exhibited a distinct <111>ai texture. The interface betw een β-Si3N4w and A1 was in a good bonding status without voids and reaction products. Effects of extrusion process on the mechanical properties of com posites were also investigated. The results indicated the extrusion process had a prom inent strengthening effect on the mechanical properties of composites. The maxim umyield strength and ultim ate tensile strength of com posites reached up to 170 and 289 MPa, respectively, accompanied by a 12.3% elongation at fracture w hen the w hisker fraction was 15 vol.%. This im provem ent 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.%β-Si3N4w corresponded well w ith the theoretical value from different strengthening mechanisms.

The β-Si3N4whiskers（β-Si3N4w） reinforced Al matrix composites were first fabricated by hot pressing,then treated through hot extrusion. The microstructure characterization demonstrated the preferred orientations of both β-Si3N4w and Al grains in the as-extruded composites. It indicated that β-Si3N4w were aligned along the extrusion direction and Al grains exhibited a distinct <111>Al texture. The interface between β-Si3N4w 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.% β-Si3N4w corresponded well with the theoretical value from different strengthening mechanisms.