In situ TEM observation of the martensite interface movement on heating-cooling-heating of the pre-deformed NiTi shape memory alloy

The aim of the study is the observation of the martensite interfaces movement in pre-deformed NiTi shape memory alloy in situ on temperature variation in transmission electron microscopy. The Ni50Ti50 alloy with a thickness of 0.12 mm was pre-deformed by 10 % tension in the martensite state and unloaded. The thin foils were prepared to study the movement of the martensite interfaces on heating - cooling - heating in-situ in TEM. It is found that during the first heating, the martensite interfaces start moving at high temperatures; hence, they lose their mobility during the pre-deformation procedure. The martensite plates that appear on the second cooling keep their orientation but consist of thin twins. The movement of martensite interfaces on the second heating starts at low temperatures, and it is observed to be inverse to movement during the second cooling. This shows that the interfaces can move easily on the second heating; hence, their mobility has been restored after the first heating.

Automated summary

The aim of this study was to observe the movement of martensite interfaces in pre-deformed NiTi shape memory alloy during temperature variation using transmission electron microscopy (TEM). The Ni50Ti50 alloy was pre-deformed by 10% tension in the martensite state and then unloaded. Thin foils were prepared for in-situ TEM analysis of the movement of martensite interfaces during heating-cooling-heating cycles. The results showed that the martensite interfaces started moving at high temperatures during the first heating, lost their mobility during pre-deformation, and regained their mobility after the first heating.