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<p>The austenite–martensite (A–M) interface is found to influence the formation and evolution of martensite variants during austenite to martensite phase transformation, which can help achieve a stress-free two-way memory in Ni–Mn–Ga shape memory alloys (SMAs). However, the underlying mechanism of the interface effects on phase transformation requires further research. This study investigates the A–M interface-dependent martensite states during temperature-driven complete transformation (CT) and incomplete transformation (IT) of the most popular NiTi SMA using molecular dynamics simulation. It is found that, in the IT case, the residual A–M interface in NiTi single crystal after IT heating can serve as the backward transformation interface, promoting the formation of a single martensite variant during cooling and enabling stress-free two-way memory. In contrast, this is not always observed in the CT case. This phenomenon can be attributed to the higher stress gradient of the residual A–M interface induced strong constraint and the formation of non-self-accommodating single martensite variant in cooling of the IT case. The results indicate that modulating the properties of the transformation interface could be a promising approach for achieving robust stress-free two-way memory in NiTi SMAs.</p>

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Transformation interface effect on shape memory behavior of single-crystal NiTi: a molecular dynamics study

  • 期刊论文

  • 发表日期：

    2025年1月7日

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  • Aimeng Zhang,
  • Su Chen,
  • Fa Wu,
  • Chun Li,
  • Shaobin Zhang

摘要

The austenite–martensite (A–M) interface is found to influence the formation and evolution of martensite variants during austenite to martensite phase transformation, which can help achieve a stress-free two-way memory in Ni–Mn–Ga shape memory alloys (SMAs). However, the underlying mechanism of the interface effects on phase transformation requires further research. This study investigates the A–M interface-dependent martensite states during temperature-driven complete transformation (CT) and incomplete transformation (IT) of the most popular NiTi SMA using molecular dynamics simulation. It is found that, in the IT case, the residual A–M interface in NiTi single crystal after IT heating can serve as the backward transformation interface, promoting the formation of a single martensite variant during cooling and enabling stress-free two-way memory. In contrast, this is not always observed in the CT case. This phenomenon can be attributed to the higher stress gradient of the residual A–M interface induced strong constraint and the formation of non-self-accommodating single martensite variant in cooling of the IT case. The results indicate that modulating the properties of the transformation interface could be a promising approach for achieving robust stress-free two-way memory in NiTi SMAs.