Influence of the Ti content, training cycles and pre-strain on the two-way shape memory effect in NiTi alloys

In this article, the effect of titanium content in the range of 49.9–50.8 at.%, number of training cycles and the amount of pre-strain on the two-way shape memory effect (TWSME) of TiNi shape memory alloy were investigated. So four ingots with compositions of Ni–49.9at%Ti, Ni–50.5at%Ti, Ni–50.7at%Ti and Ni–50.8at%Ti were prepared from technically pure metals by using vacuum induction melting. The transformation temperatures were obtained by DSC. The results showed that MS temperature increases slithery with increasing in Ti content. Optimum number of training cycle and pre-strain were obtained, 10–15 cycles and 16% respectively. Also it was found that TWSME increases with decreasing in Ti content.

► With increasing in Ti content of Ti-rich alloys, volume fraction of Ti2Ni precipitates increase.
► The maximum εtw decreases with increasing the amount of Ti in composition.
► The εtw increases rapidly in the first training cycles (1-5 cycles) and then almost does not change.
► The εtw increased with increasing pre-strain to a maximum value at 16% pre-strain, then decreased.