Influence of Annealing Time and Thermo-Mechanical Cycling on Constrained Recovery Properties of a Cold-Worked NiTi Wire

摘要

In this work, the influence of parameters such as annealing time, pre-strain and thermo-mechanical cycling on recovery stresses of NiTi wires has been investigated by using a dynamic mechanical analyzer. The results show that the maximum recovery stress decreases with increasing annealing time and increases with increasing pre-strain except for 60-min annealed sample with 4 pre-strain, which has a higher recovery stress than 45-min annealed sample with the same pre-strain. The recovery stresses drastically increase during the first two thermo-mechanical cycles for all samples, regardless of annealing time. The observed changes of recovery stress could be attributed to different transformation temperatures and mechanical properties induced by different annealing times and/or thermo-mechanical cycling.