Significant improvements of the relative density, microhardness, and fracture toughness of SiC via the addition of Ni3Al and Mg2Si

Abstract SiC ceramics were sintered with Mg2Si and Ni3Al additives at 900–1300 °C. Densification was achieved at temperatures as low as 1300 °C, and the microhardness and fracture toughness were significantly improved from 4.95 GPa to 8.17 MPa m1/2 for the ceramic without Ni3Al to 13.59 GPa and 10.40 MPa m1/2 for the ceramic sintered with 10 wt% Ni3Al, representing improvements of 174.55% and 27.29%, respectively. Some of the Ni3Al was converted into Ni with a (110)Ni3Al || (002)Ni crystal morphology, and the SiC bonded to Ni3Al with a (103)SiC || (112)Ni3Al crystal morphology. These well-matched crystal morphologies led to perfect lattice coherence. The Ni-rich regions prevented the elongation of cracks, resulting in improved fracture toughness.