Mechanical properties and interfacial microstructure of SiC whisker-reinforced ZrO 2Y 2O 3 composites

Abstract

Mechanical properties and fracture mechanisms of 20 vol% SiC whisker-reinforced ZrO 2 (Y 2O 3) composites were investigated. The phase composition, fractography and the microstructure of the whisker-matrix interface were studied by XRD, SEM, TEM and HREM. The results show that flexural strength and fracture toughness of SiCw ZrO 2 (with 2 mol% Y 2O 3) composites increase by 453 MPa and 2.6 MPa m 1 2 , respectively. However, in the composites with 6 mol% Y 2O 3, the increment is only 17 MPa and 1.6 MPa m 1 2 , respectively. It reveals that the ZrO 2 (2 mol% Y 2O 3) composites have a good toughening effect by incorporating SiC whiskers. HREM observations indicate that the whiskers in ZrO 2 (2 mol% Y 2O 3) composites are directly bonded with the ZrO 2 matrix, only few atom disorder zones exist at the interface. In contrast, for ZrO 2 (6 mol% Y 2O 3) composites, there is a thin, uniform layer of amorphous phase at the interface between SiC whisker and ZrO 2 matrix, indicating that high Y 2O 3 content promotes the formation of an interfacial layer. The study of fracture surfaces by SEM indicates that the main toughening mechanisms in SiCw ZrO 2 (with 2 mol% Y 2O 3) composites are crack deflection, crack bridging, whisker pull-out and dynamic t→m transformation. Crack deflection is the main toughening mechanism in SiCw ZrO 2 (with 6 mol% Y 2O 3) composites.