Atomistic simulation on the generation of defects in Cu/SiC composites during cooling

Abstract

The coefficient of thermal expansion (CTE) mismatch between the reinforcement and the matrix results in thermal residual stresses and defects within metal-matrix composites (MMCs) upon cooling from the processing temperature to ambient temperature. The residual stresses and thermally induced defects play an important role in the mechanical properties of MMCs, it is critical to understand the mechanism of defect formation and evolution. This study provides atomistic simulations to reveal the generation of thermal residual stresses, dislocation and incomplete stacking fault tetrahedron (ISFT) during cooling in the idealized Cu/SiC composites. We found that dislocations are generated explosively in a certain temperature range during cooling, which results in a non-linear relationship between dislocation density and temperature. The combined effect of the stresses induced by CTE mismatch and the thermodynamic state of the metal leads to the rapid generation of dislocations. The Shockley partial and the highly stable stair rod are the two dominant dislocation structures. The immobile stair-rod dislocations and the highly stable ISFTs formed in the initial high temperature stage inhibit further development of plastic deformation. The present results provide new insights into the defect formation mechanism and the dislocation strengthening mechanism of MMCs caused by thermal mismatch between constituents.