Effect of the in-situ formed CuO additive on the fracture behaviour and failure mechanism of Ag-SnO2 composites

Oxide additives can significantly improve the mechanical properties of ceramic particle -reinforced metal matrix composites. In this study, the fracture behaviour and failure mecha-nism of the Ag-SnO2 composites without and with in-situ formed CuO additive are investigated using in-situ scanning electron microscope (SEM) and numerical simulation. The results show that the CuO additive significantly enhances the fracture toughness of the Ag-SnO2 composite. The initiation and propagation of secondary cracks near the primary crack tip are effectively inhibi-ted, and large dimples are formed around SnO2 particles. The improvement in the mechanical properties is attributed to the stress concentration relief in the Ag matrix and enhanced interfacial strength. Interface debonding at the sharp corners of the SnO2 particles initiates the formation of cracks in the Ag-SnO2 composite without CuO. The initiated cracks propagate through the high -stress concentration region at an angle of 45 degrees to the loading direction, resulting in a matrix fracture. For the Ag-SnO2 composite with CuO nanoparticles, the propagation rate of the primary cracks reduces significantly, and microcracks are primarily induced near clustered SnO2 particles. Moreover, the damage initiation shifts from the SnO2/Ag interface to the Ag metal matrix with reduced SnO2 particle aggregation in the Ag-SnO2(CuO) composite.