Atomistic simulation of martensitic phase transformation at the crack tip in B2 NiAl

Mechanisms of low-temperature deformation at the crack tip in B2 NiAl are studied by molecular dynamics simulations. The stress-induced martensitic transformation is found to occur at the crack tip when a sufficiently high stress concentration exists. For cracks with 〈1 0 0〉 crack fronts, the layered structures of martensites are formed at the crack tip, which is caused by the atoms’ relative displacement on a basal plane due to the shear stress at the crack tip. The mechanism of the martensitic transformation from the B2 to the L1₀ structures occurs along the Bain path. For cracks with 〈1 1 0〉 crack fronts, the martensitic transformation occurs without any layered structures existing. The phase transformation is caused by the atoms’ relative displacements at different atoms layers in the entire martensite formed region.