Abstract
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 transformation 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 μs the transformation is undetectable. Then, a rapid transformation occurs near the surface and saturates after 9 μs. The evolution of the transformation in the bulk becomes discernible only after the transformation near the surface completes and lasts for approximately 40 μs.
Original language | English |
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Journal | Journal of Alloys and Compounds |
DOIs | |
State | E-pub ahead of print - 1 Nov 2020 |
Keywords
- large-driving-force
- Shape memory alloys
- Reverse martensitic transformation
- synchrotron
- X-ray diffraction