The influence of thermal cycling on the transition temperatures of a Fe-Mn-Si shape memory alloy

• Published in: Materials science & engineering. A, Structural materials : properties, microstructure and processing Structural materials : properties, microstructure and processing, 1999-12, Vol.273, p.512-516
• Main Authors: Andrade, M.S, Osthues, R.M, Arruda, G.J
• Format: Article
• Language: English
• Subjects: Fe-Mn-Si alloys; Magnetic transition; Martensitic transformation; Microstructure; Shape memory alloys; Thermal cycling
• ISSN: 0921-5093; 1873-4936
• DOI: 10.1016/S0921-5093(99)00390-1

Depending on their composition, Fe-Mn-Si based alloys can exhibit, upon cooling, a martensitic transformation, γ (FCC) ↔ ε (HCP), and a magnetic transition from paramagnetic to antiferromagnetic, at the Néel temperature, T N. is said to increase the stability of the γ phase, depressing M S to quite lower temperatures. In this work, the phase transition temperatures were measured on a Fe-27 wt.% Mn-2.5 wt.% Si alloy by differential scanning calorimetry and by dilatometry after thermal cycles performed in the range 77 up to 623 K. The aim was to study the effects of thermal cycling on the transformation temperatures M S, M F, A S, A F and T N. It was observed that, although T N was above and close to M S, the martensitic transformation was not suppressed on cooling. Besides that, depending on the temperature and time, the alloy remained above A F, the M S temperature was lowered, the A F was slightly increased, while T N remained constant. It was also observed that thermal cycling below M S and above A F can suppress further martensitic transformation, which can be recovered after heating to 1323 K. These observations are discussed in terms of composition and elastic strain changes generated during thermal cycling.