LOAD-INDUCED MARTENSITIC TRANSFORMATIONS IN PSEUDO-ELASTIC LENNARD-JONES CRYSTALS

We present molecular dynamics (MD) simulations of a load-induced martensitic phase transformation in pseudo-elastic Lennard-Jones crystals. The model material exhibits martensitic transformations between cubic and hexagonal lattice structures in 2D which represent austenite and martensite. Under axial loading two martensite variants are favoured out of four generic variants possible with this model. In nucleation-and-growth processes the formation of martensite domains are observed in MD simulations and the reverse process upon unloading. Two possible re-transformation mechanisms are identified, a reversible and a reconstructive type. Reversible re-transformations conserve the reference unit cells, while the reconstructive mechanism involves the generation of dislocation motions which destroy the reference unit cells by slip. Both types re-establish the square lattice. While the reversible type represents the predominant reverse transformation mechanism, the reconstructive type is of special importance because it produces lattice defects, and plastic deformation which change both the evolution of subsequent transformation cycles and the magnitude of the phase transformation load.