Effect of graphene layers on the thermomechanical behaviour of a NiTi shape memory alloy during the nanoscale phase transition

Graphene layers (graphite) were deposited on the surface of a NiTi shape memory alloy to enhance the deformation and nanoscale phase transition volume. One highly polished NiTi and one with the graphite deposit were examined. The graphite-coated NiTi showed deeper nanoindentation depths during the solid-state phase transition, especially in rate-dependent zones. Larger superelastic deformation confirmed that nanoscale latent heat transfer through the deposited graphite allowed a larger phase transformed volume in the bulk and, therefore, greater stress relaxation and a greater indentation depth.