Effects of the CuO additive nanoparticles on the internal strain homogenization and microstructure evolution in Ag-SnO2 composites

Abstract

Stress concentration caused by reinforcements has very unfavorable effects on the metal matrix composites, which will inevitably induce localized strains and crack initiation. In this paper, an effective approach is presented to relieve stress concentrations near the reinforcements in metallic composites. The Ag-SnO2 contact materials with CuO additive are prepared by electroless plating combined with powder metallurgy method. The CuO nanoparticles in-situ formed on the SnO2 reinforcements are adopted to relieve local stress concentrations near the Ag/SnO2 interfaces and promote strain homogenization. The mechanical properties, deformation characteristics and microstructure evolution of the Ag-SnO2 composites without and with CuO additive are systematically studied by experiments and numerical simulations. The results show that the CuO nanoparticles formed on the surfaces of the SnO2 reinforcements dramatically improve the mechanical properties of the Ag-SnO2 composites, particularly the plasticity at a higher loading rate. The ultimate strength of the Ag-SnO2(CuO) tensile specimens is increased from 104 to 127 MPa, and the uniform elongation is increased by 83% compared with that without CuO. It is demonstrated that the dislocation tangle around the CuO nanoparticles effectively relieves the adverse effect of the stress concentration near the SnO2 and results in the strain homogenization in the Ag matrix. Furthermore, the damage evolution of the Ag-SnO2 composites without and with CuO nanoparticles is investigated by the Gurson-Tvergaard-Needleman (GTN) models under uniaxial tension. The error range of the simulated stress-strain curves is lower than 4%. The nucleation and growth of voids at the interfaces of the Ag-SnO2 composites are numerically simulated and discussed. This study provides a fundamental basis for developing novel high-performance metal matrix composites.