Relationships between martensite transformation temperatures and compositions in Fe-Mn-Si-based shape memory alloys

摘要

The correlation between γ ↔ ϵ martensite transformation temperatures (M_s, A_s), the thermal hysteresis (A_s - M_s) and the alloy compositions has been determined by using the multiple linear regression method based on existing experimental data for Fe-Mn-Si-based shape memory alloys. The empirical quantitative equations are: M_s (K) = 282 - 6.3Mn + 37.2Si - 8.1Cr - 6.3Ni; A_s (K) = 502 - 5.1Mn + 7.8Si - 4.3Cr - 9.2Ni; A_s - M_s (K) = 220 + 1.2Mn - 29.4Si + 3.8Cr - 2.9Ni (the alloy compositions are in weight per cent.) It has been demonstrated that the addition of Mn, Cr and Ni tends to lower the martensite transformation temperatures, but Si tends to increase them markedly. This agrees quite well with previous results which indicate that Mn, Cr and Ni increase the stacking fault energy of these alloys while Si decreases it. Moreover, the transformation thermal hysteresis decreases with increasing Si and Ni concentration but increases with increasing Cr and Mn content. The above-mentioned results are very useful for the composition design of this type of alloy.