EFFECTS OF RECRYSTALLIZATION AND GRAIN-SIZE ON THE MARTENSITIC-TRANSFORMATION IN FE-31-PERCENT-MN-5-PERCENT-SI ALLOY

The effects of recrystallization and grain size have been studied in a n 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 homogen ized 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 homogeniz ed in the same way as the former followed by a compression and a subse quent recrystallization at 1323 K for 30 min. The only difference betw een the samples is the plastic deformation induced by the compression. We thus conclude that some effect of the compressive deformation rema ins despite the recrystallization and suppresses the subsequent marten site formation. However, we have not yet been able to identify this ef fect. This matter will be subject to further investigations. No signif icant change is found in the M(S) and A(S) temperatures for the gamma <---->epsilon transformations determined by DSC. When the grain size v aries between 40 and 160 mu m in completely recrystallized samples the variation in transformation temperatures is small, less than 10 K.