The evolution of the martensitic transformation at the high-driving-force regime: A microsecond-scale time-resolved X-ray diffraction study

The reverse martensitic transformation proceeds through several sub-processes at various length and time scales. We study the transformation kinetics at the high thermodynamic driving force regime, by inducing a rapid heating-pulse in a shape memory alloy wire. We track the evolution of the trans formation at the microsecond scale by multi-frame time-resolved X-ray diffraction at synchrotron radiation with simultaneous high-bandwidth force measurements. The x-ray probed a narrow region at the periphery of the wire, while the force was a measure for the transformation-induced stress in the bulk of the wire. We reveal three stages occurring at different times and length-scales in the material. During the first 5 mu s the transformation is undetectable. Then, a rapid transformation occurs near the surface and saturates after 9 mu s. The evolution of the transformation in the bulk becomes discernible only after the transformation near the surface completes and lasts for approximately 40 mu s. (C) 2020 Elsevier B.V. All rights reserved.

Automated summary

Researchers studied the reverse martensitic transformation in a shape memory alloy under high thermodynamic driving force regime, tracking the evolution of the transformation at microsecond scale using time-resolved X-ray diffraction and force measurements.