Strain glass transition of NiTi alloy induced by selective laser melting technology

The 3D printing of martensite NiTi alloys has gained popularity because the resulting shape memory effect advances technology from 3D to 4D printing. In this study, we report an interesting phenomenon: a martensite NiTi alloy transforms into a strain glass alloy (STG) after 3D printing via selective laser melting (SLM). The long-range strain order of the martensite disappeared in the SLM-printed NiTi alloy during cooling. Instead, the SLM-printed NiTi alloy exhibited typical strain glass signatures, including invariance of the average structure, dynamical freezing, non-ergodicity, and local symmetry breaking. The origin of the strain glass transition in the SLM-printed NiTi alloy was attributed to point defect doping caused by composition variation. This study enriches our understanding of phase transformation through 3D printing.