Constrained recovery properties of NiTi shape memory alloy wire during thermal cycling

• The self-assembled setup used for testing in this research is novelty.
• Increasing pre-strain will increase recovery stress, especially from 4% to 8%.
• The first partial thermal cycle had less effect on the second full thermal cycle.

The present research aims to better understand the influence of pre-strain and thermo cycling on recovery stress and transformation temperatures of Ni50.2Ti49.8 (at.%) shape memory alloy wire. A self-assembled setup was used to perform the experiments. The amount of detwinned martensite and dislocations result in an increase of recovery stress and the As′ with increasing pre-strain. With 8% pre-strain, the recovery stress and As′ sharply decreased in the initial thermal cycles, and then slowly decreased before reaching a steady state with increasing thermal cycle number. The first partial thermal cycle had less effect on the recovery behavior of second full thermal cycle.