Ni nanosegregation reduces temperature dependence of stress-induced martensitic transformation in Ni50.9Ti49.1 shape memory alloy

HC Chu and ZH Zhao and JY Fang and Y Xiao and JP Lin and JY Min, JOURNAL OF MATERIALS RESEARCH AND TECHNOLOGY-JMR&T, 35, 4996-5003 (2025).

DOI: 10.1016/j.jmrt.2025.02.175

Temperature dependence of stress-induced martensitic transformation (SIMT) is crucial to the thermomechanical response of superelastic NiTi shape memory alloy. We experimentally verified that the temperature dependence of the critical stress for SIMT reduces from 6.8 +/- 0.2 MPa K- 1 to 5.0 +/- 0.1 MPa K- 1 in superelastic Ni50.9Ti49.1 after aging at 523 K for 24 h. Systematic atomistic simulation indicates that a strong lattice distortion induced by age-induced Ni nanosegregation can inhibit growth of martensite embryo during SIMT. This effect is more pronounced as temperature decreases and therefore the critical stress for SIMT is increased more at low temperature than high temperature, which is the underlying mechanism for the reduced temperature dependence of SIMT. Our finding paves a new way to regulate the thermomechanical performance of superelastic NiTi through low-temperature aging.

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