Atomic-scale strengthening mechanism of dislocation-obstacle interaction in silicon carbide particle-reinforced copper matrix nanocomposites

Using molecular dynamics (MD) simulations, the strengthening mechanism of silicon carbide (SiC) particle acted as barrier for the motion of edge dislocation in copper (Cu) matrix nanocomposites under shear loading is investigated. The dislocation glide behavior and the dislocation-particle interaction accounting for the effect of the temperature and the particle size are discussed in terms of the stress-strain relationship, the crystal energy change, the stress distribution and the dislocation evaluation. The results show that the critical depinning stress and the critical depinning strain are found to vary significantly depending upon the temperature and the particle size, consistent with previous studies. Higher temperature or smaller particle results in lower critical depinning stress to allow dislocation to bypass particle. Moreover, the critical depinning stress from the current atomic study is lower than the theoretical value due to the presence of cross-slip and thermal activation. At low temperature the mechanical activation controls the depinning stress of the dislocation bypassing particle, while at high temperature the thermal activation dominates that. In addition, the trapping sites of dislocations for the dislocation multiplication are observed at high temperature or large particle, due to the lattice mismatch of particle taken as the dislocation source. Compared to the dislocation interacting with void or metal-particle, the interaction of dislocation and SiC-particle in Cu + SiC nanocomposite reveals much complex factors, such as the multiple glide planes, the nanosize effect, as well as the coupling effect of mechanical and thermal activation, on the strengthening mechanism. It maybe apply these results to a high throughput experimental design which provides the dense and targeted material data, to accelerate material discovery with the large-scale and low-cost fabrication strategies.