Influence of pre-strain on recovery stress of annealed NiTi thin wire during isothermal holding

The present research aims to understand the recovery stress of NiTi wires generated during heating and isothermal holding under constrained condition. Both pre-strain and isothermal holding temperature have significant effects on the evolution of recovery stress during heating and isothermal holding. In general, increasing isothermal holding temperature and/or pre-strain causes an increase of recovery stress reduction or relaxation. This effect can be attributed to different dislocation densities and mobility of dislocations generated in those conditions.

Research highlights▶ The generation and evolution of recovery stress in annealed NiTi wires depend on the pre-strain level and isothermal holding temperature. ▶ Increasing isothermal holding temperature and/or pre-strain causes the increase of recovery stress reduction. ▶ This effect can be attributed to a different dislocation density and mobility of dislocations generated in different conditions.