Influence of Composition and Thermomechanical Training Process on the Transformation Behavior and Shape Memory Properties of NiTi Based Alloys

The effects of composition, specially the Cu element and thermomechanical training process on the transformation and one way shape memory behavior (OWSM) of NiTi based alloys were investigated using differential scanning calorimetry and microstructural analysis. The hot rolled strips with different compositions were trained under various applied pre-strains by bending test at martensitic state. It was found that the presence of Cu in the NiTi alloy results in an improvement of the OWSM effect by reducing the transformation hysteresis and forming the longer martensitic variants with lower interfacial energy than the NiTi binary alloys. Increasing the applied pre-strain and the number of thermomechanical training cycles caused OWSM effect to decrease. Although the transformation temperature increased at the higher applied pre-strain, it was reduced during the thermomechanical training process.