Molecular dynamics simulations to the pseudo-elasticity of NiTi shape memory alloy nano-pillar subjected to cyclic compression

The pseudo-elasticity of equiatomic NiTi shape memory alloy (SMA) nano-pillar subjected to a uniaxial cyclic compression is investigated by molecular dynamics (MD) simulation. By analyzing the local atomic structure, the nucleation sites and propagation paths of martensite transformation and its reverse, the degeneration of pseudo-elasticity and the interaction between martensitic transformation and defects at nano-scale during cyclic compressive deformation are discussed. It is indicated that the nucleation sites and propagation paths of the reverse transformation in the process of unloading are different from that observed in the process of loading (i.e., compression), and the dislocation and twinning are responsible for the changes in the atomic structure and mechanical response, the accumulated irreversible strain and the degeneration of pseudo-elasticity.