Strain glass in Sn-doped NiTi shape memory alloys

Abstract

In this study, we presented the discovery of strain glass (STG) in Ni49.4Ti50.6−xSnx shape memory alloys (SMAs). The findings highlighted a significant advancement in the understanding of the structural and functional properties of NiTi-based SMAs. A phase diagram was established based on experimental results, demonstrating the occurrence of a crossover from martensitic state to STG state in Ni49.4Ti50.6−xSnx alloys, with transition temperature depending on the Sn content. For an Sn content x < 2.5, the Ni49.4Ti50.6−xSnx alloys underwent conventional B2 → B19′ martensitic transformation, and the transformation temperatures decreased with increasing the Sn content. When x ≥ 2.5, the STG transition appeared. Additionally, the shape memory effect (SME) and wide-temperature-range superelasticity (SE) were found in the NiTiSn STG alloy at sub-room temperatures. This finding broadens the scope of SME and SE and holds potential for applications in low-temperature space environments.