Comparison of thermally induced and deformation induced martensite in Fe-29% Ni-2% Mn alloy

The morphology and crystallography of maitensite either formed by cooling to subzero temperatures (thermal effect) or by compression deformation were compared for different austenite grain sizes of Fe-29% Ni-2% Mn alloy by transmission electron microscope (TEM). TEM observations revealed both epsilon and alpha' martensite formation within large grained austenite phases by thermal effect whereas only alpha' martensite formation was observed in small grained austenite phases. On the other hand, compression deformation effect caused only a' martensite formation in both small and large grained austenite phases of Fe-29% Ni-2% Mn alloy. Thermally induced alpha' martensite exhibited a lenticular morphology with partial twinnings that are peculiar to this kind of morphology. The crystallographic orientation relationship between austenite and thermally induced alpha' lenticular martensites was found to be as Kurdjumov-Sachs (K-S) type relationship. (c) 2006 Elsevier B.V. All rights reserved.