Effect of the Neel temperature, TN, on martensitic transformation in Fe–Mn–Si-based shape memory alloys

Internal friction and elastic modulus of Fe–30.30 Mn–6.10 Si, Fe–29.05 Mn–6.27 Si–0.024 RE (rare earth elements) and Fe–26.40 Mn–6.02 Si–5.20 Cr shape memory alloys were measured as a function of temperature from 150 to 600 K using an electrostatic audio-frequency internal friction instrument. The Neel temperature, TN, and Ms temperature of these alloys were determined. By calculating the area covering the internal friction peak of the ε→γ reversion transformation, effects of the Neel temperature, TN, on the γ→ε martensitic transformation were investigated. The results show that alloy compositions evidently affect the TN temperature, and RE and Cr reduce the TN temperature. With the decrease of the TN temperature and the increase of Ms–TN, the repressive effect of the TN temperature on the γ→ε martensitic transformation decreases, and the amount of the martensitic ε phase and the area of the internal friction peak of the ε→γ transformation increase.