Effect of Cu addition on the high temperature shape memory properties of Ti50Ni25Pd25 alloy

The effects of Cu addition, replacing Ni in a Ti50Ni25Pd25 alloy, on the microstructure, mechanical properties and shape memory characteristics are investigated. The addition of Cu slightly enhances the strength of B19 martensite through solid solution strengthening mechanism, without deteriorating the strain to fracture. The addition of Cu slightly increases the transformation temperatures but does not affect the thermal hysteresis (13 K). Results of thermal cycling tests under various constant stress levels reveal that the addition of Cu significantly increases the resistance against plastic deformation at high temperatures and at high stress levels (i.e. >450 MPa) indicating a relatively better creep resistance and stable cyclic response. TiNiPdCu alloys show better dimensional stability and demonstrate better recovery ratio upon thermal cycling as compared to that of ternary TiNiPd alloys.

► The addition of Cu increased the transformation temperatures while maintaining a small thermal hysteresis. ► The addition of Cu increased the strength without affecting the inherited ductility of TiNiPd alloys. ► The addition of Cu increased the dimensional stability and improved the recovery strain.