Effect of alumina morphology on flash sintering and mechanical properties of 3YSZ/Alumina composites: whiskers vs powders

Abstract

In this paper, 3YSZ/alumina composites containing different content of alumina with different forms (powders and whiskers, respectively) were fabricated by flash sintering. The flash sintering behavior and mechanical properties of the composites were characterized and were compared with those prepared by conventional sintering. The onset temperature of the 3YSZ/alumina whiskers composites was lower than that of the 3YSZ/alumina powders composites with identical alumina content. The reason can be attributed to electrical conductivity; the conductivity of the former was lower than that of the latter. For the 3YSZ/alumina powders composites which can be densified by conventional sintering method, their relative density, Vickers hardness and fracture toughness were comparable to those prepared by flash sintering. While for the 3YSZ/alumina whiskers composites where constrained sintering existed, the flash sintering method revealed obvious advantage over the conventional sintering. A relative density of 94.5%, hardness of 13.77 GPa and fracture toughness of 5.36 MPa·m1/2 were obtained for the flash sintered 3YSZ/ 30 vol.% alumina whisker composites. In contrast, the relative density, hardness, and fracture toughness of the conventional sintered ones were 86.4%, 11.60 GPa and 4.82 MPa·m1/2, respectively.