Mechanical response of nitrogen ion implanted NiTi shape memory alloy

• The effect of ion implantation process on shape memory alloy was investigated.
• In the implantation process both surface layer and bulk material are modified.
• The microstructure is modified and superelastic effect is destroyed in surface layer.
• The parameters of superelastic phenomena are changed in bulk material.

In the paper a change of material (mechanical) parameters of NiTi shape memory alloy subjected to ion implantation treatment is investigated. The spherical indentation tests in micro- and nano-scale and tension test have been performed to study an evolution of local superelastic effect in different volumes of nonimplanted and nitrogen ion implanted NiTi alloy. The differential scanning calorimetry has been applied to measure the change of characteristic temperatures due to ion implantation treatment. The structure of implanted material has been investigated using electron microscopy technique. It has been found that the ion implantation process changes the properties not only in a thin surface layer but also in bulk material. In the layer the pseudoelastic effect is destroyed, and in the substrate is preserved, however its parameters are changed. The characteristic phase transformation temperatures in substrate are also modified.