Abstract:

Effect of multiple direct and reverse martensitic transformations on fragmentation of austenitic grains in FeeNi alloys have been studied by X-ray diffraction and scanning electron microscopy. An ultra-fine structure was formed by fragmentation inside austenitic grains due to progressing misorientation of austenitic sub-grains during multiple γ-α-γ-martensitic phase transitions. An increase in the number of  γ-α-γ-transformations increases misorientation angle between austenitic sub-grains and leads to transformation of an austenitic single crystal into a textured polycrystal. It has been shown that multiple  γ-α-γ-martensitic phase transitions change the mechanism of internal stress relaxation from dislocation-based to deformation twinning.

Key words: Austenite, Crystal lattice, Ultra-fine structure, Martensitic transformation