Shear induced chemical mixing in heterogeneous systems

Shear-induced mixing in heterogeneous Cu alloy systems was investigated by molecular dynamics simulation. Each system, which comprised a single spherical particle within a Cu matrix, was subjected to cyclical shearing events to high strains at 100 K. The particles investigated were Cu, Ag, Ni, Fe, Nb, and V. fcc particles were observed to undergo "superdiffusive" mixing with dislocations crossing the particle-matrix interface. The initial rate of mixing in these systems increased quadratically with particle radius. bcc particles showed different behaviors. For Nb and V dislocations did not cross into the particles and the initial rates of mixing increased linearly with particle radius. The Nb particles remained spherical but developed amorphous Cu-Nb shells at the particle-matrix interface. The V particle showed some faceting, but it too formed amorphous layers on non-facetted interfaces. The Fe particle behaved similarly to Nb and V particles initially, but more like fcc particles at high strains. The molecular dynamics results are compared with experimental observations.