Atomistic study on the phase transformation in NiTi under thermal cycling

- Completely reversible phase transformations in NiTi alloy are observed.
- The various martensitic twins are found at low temperature.
- Three types of detwinning manners in NiTi have been discussed.

In this work, the phase transformations induced by thermal cycling between 500 K and 4 K in NiTi are investigated based on molecular dynamics simulations. Completely reversible phase transformations are observed. The B2 phase is found to be always a single crystal at high temperature while single crystal and twinned martensitic phases are observed at low temperature. The martensitic phase transformation completes at about 300 K while various types of martensitic phases are found during the cooling process. In the reverse martensitic transformation, twins are found to be able to decrease the austenite start temperature. Furthermore, three types of detwinning manners related to the thermal hysteresis of NiTi have been discussed.

214