Critical point of martensitic transformation under stress in an Fe-31.2Pd (at.%) shape memory alloy

Abstract

We have examined the transformation strain, Δε, in the [0 0 1] direction of an Fe-31.2Pd (at.%) shape memory alloy under compressive stress applied in the same direction. When the stress is absent, the alloy exhibits a cubic to tetragonal martensitic transformation at 230 K with |Δε| of 1.4%. As the stress increases, the transformation temperature increases linearly and |Δε| decreases linearly and vanishes at 40 MPa (280 K). This point is the critical point of this transformation at which the first-order nature disappears, and the critical exponent β is evaluated to be 0.47 ± 0.04.

Keywords:

• phase diagrams
• mechanical properties
• diffusionless transformations
• Fe-based alloys
• martensitic transformations
• solid-state transformation
• structural transitions
• thermal expansion

Disclosure statement

No potential conflict of interest was reported by the authors.

Acknowledgements

One of the authors, F.X., expresses gratitude to Prof. Xuejun Jin in Shanghai Jiao Tong University.

Additional information

Funding

This work was supported by the Japan Society for the Promotion of Science [grant number 23360280], [grant number 26289230].