Insights into the martensitic transformation kinetics and mechanical properties of quaternary Ti–Ni–Nb–V shape memory alloys

Abstract

The effect of V addition on the microstructural evolution, martensitic transformation behaviors and mechanical performances of Ti–Ni–Nb shape memory alloys was systematically investigated. The results reveal that the phase remains almost equal in Ti–Ni–Nb–V shape memory alloys, irrespective of the V content. With increasing V content, the amount of β-Nb phase is increased, which further leads to a reduction in the interspace and width of the β-Nb phase. When the V content changes, Ti–Ni–Nb–V shape memory alloys possess a single stage B2⇌B19´ martensitic transformation. In addition, the martensitic transformation temperatures first increase and then decrease owing to the variation in the chemical composition of the TiNi matrix and microstructural features as the V content increases. The higher yield strength of Ti–Ni–Nb shape memory alloys can be obtained by adding a moderate V content. In conclusion, the lower martensitic transformation temperature and the higher yield strength can be tailored by optimizing the V content in Ti–Ni–Nb shape memory alloys, which would further widen their application fields.