Effects of recrystallization and grain size on the martensitic transformation in Fe-31%Mn-5%Si alloy

The effects of recrystallization and grain size have been studied in an Fe-31%Mn-5%Si shape memory alloy. The amount of martensite formed in samples which have been hot rolled at 1373 K and subsequently homogenized for 24 h at 1273 K followed by a final 30 min anneal at 1323 K is twice as large as in samples which have been hot rolled and homogenized in the same way as the former followed by a compression and a subsequent recrystallization at 1323 K for 30 min. The only difference between the samples is the plastic deformation induced by the compression. We thus conclude that some effect of the compressive deformation remains despite the recrystallization and suppresses the subsequent martensite formation. However, we have not yet been able to identify this effect. This matter will be subject to further investigations. No significant change is found in the M(S) and A(S) temperatures for the gamma <---->epsilon transformations determined by DSC. When the grain size varies between 40 and 160 mu m in completely recrystallized samples the variation in transformation temperatures is small, less than 10 K.