Crystallographic and lattice point correlations of a new hcp-to-fco martensitic transformation observed in the Ni-Hf system

A hexagonal close-packed to face-centered orthorhombic (hcp-to-fco) martensitic transformation in the Hf lattice upon dissolving Ni atoms is observed by molecular dynamics simulations based on a proven realistic Ni-Hf potential. It is proposed that the mechanism of the phase transformation takes place through four simultaneous actions, i.e. sliding, shearing, stretching and lattice constant adjusting, with a speed in an order of 100 m/s. Based on an analytical deduction, the crystallographic and lattice point correlations between the initial hcp and final fco structures are obtained, respectively, and the deduced correlations may also be of relevance for another two phase transformations: the hexagonal close-packed to body-centered tetragonal, and hexagonal close-packed to face-centered cubic martensitic phase transformations.