Molecular dynamics simulations of phase transformations in niti bicrystals

The influence of grain boundaries and grain misorientation on the nucleation and growth of martensite in an equi-atomic nickeltitanium (NiTi) shape memory alloy (SMA) is investigated by performing molecular dynamics (MD) simulations on bicrystals with a modified embedded atom method (MEAM) interatomic potential. Stress-induced martensitic transformations are simulated in bicrystals with mixed grain boundaries and the behavior of the bicrystal is compared to that of individual single crystals. Here, a particular bicrystal with < 110 > and < 111 > oriented austenite grains is chosen as an example. Results indicate that the mixed grain boundary in the austenite bicrystal acts as a nucleation site for stress-induced martensitic transformation in the grains. The deformation behavior and the transformation strain of the bicrystal fall in between those of the two corresponding single crystals.