Forced chemical mixing in immiscible alloys during severe plastic deformation at elevated temperatures

The forced chemical mixing of atoms in model immiscible alloys during severe plastic deformation (SPD) has been investigated as a function of temperature and the heat of mixing using molecular dynamics computer simulations. At low temperatures, A₇₅B₂₅ alloys form solid solutions during SPD for heats of mixing less than ∼20 kJ mol^-1, but tend to phase separate at larger values. At high temperatures these alloys show more extensive precipitation, with the precipitate morphology dependent on the heat of mixing. Analysis of the high-temperature mixing kinetics reveals that the precipitation process involves two separate mechanisms. The first derives from long-range diffusion mediated by shear-induced vacancies, while the second is due to local rearrangements of atoms induced by the forced mixing of atoms.