Causes of Partial or Complete Reversibility of Martensitic Transformation in Alloys of Iron

Abstract
Martensitic transformation implies a change in crystal structure by lattice variant shear as well as the formation of lattice defects by various amounts of lattice invariant shear. Crystallographic reversibility defines conditions under which the reverse reaction leads to the restoration of a defect-free high temperature phase (γ). This requires a lattice variant shear in opposite direction to the previous martensitic transformation. As alloys of iron are usually non-reversible a systematic study has been conducted to define the parameters which favour reversibility. Different Fe-Ni-based alloys have been studied to explore the effects of heating rates and alloying elements. The course of the retransformation is followed by DSC investigations. Optical and TEM investigations have been done to describe the change of macro- and microstructure after retransformation.