Improved superelastic stability by nanosegregation via low-temperature aging in Ti-50.9 at.% Ni shape memory alloy

ZH Zhao and JP Lin and Y Xiao and JY Min, SCRIPTA MATERIALIA, 245, 116050 (2024).

DOI: 10.1016/j.scriptamat.2024.116050

The effects of nanosegregation arising from low-temperature aging (LTA) on cyclic response of Ti-50.9 at.% Ni are investigated. Hybrid Monte Carlo/Molecular Dynamics (MC/MD) simulation indicates that the most pronounced nanosegregation is achieved by LTA at 523 K. MD simulation shows Ni cluster can impede the advancement of 011<100>(B2) dislocations, which prevail the slipping activity of NiTi, during both forward and reverse transformations due to pinning effect, so the resistance to functional degradation is promoted significantly. Experiments demonstrate that LTA at 523 K for 2 h and the resultant nanosegregation can greatly improve the superelastic stability of nanocrystalline Ti-50.9 at.% Ni, i.e. the residual strain is reduced by 50 % and the dissipation energy is increased by 200 % in LTAed sample after 50 loading-unloading cycles. These insights open possibilities for the design of SMA with outstanding cyclic stability via the combination of nanocrystalization and nanosegregation.

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