Investigations of morphological and crystallographic properties of thermally and deformation-induced martensitic phase transformations in the Fe-31.5Ni-10Mn alloy

Abstract

Martensitic transformations are diffusionless shear transformations. The transformation is usually driven by mechanical deformation or by a change in temperature. This study investigated morphological and crystallographic properties of thermally and deformation-induced austenite–martensite phase transformations in the Fe-31.5Ni-10Mn (wt%) alloy. Microstructural characterization was carried out by using a transmission electron microscope (TEM). It was seen that austenite–martensite phase transformation was $$\gamma \to \alpha ^{\prime}$$ (fcc→bcc) and the morphology of martensite was lath type. It was also determined that the habit plane of martensite was $${\left( {2~5~9} \right)_\alpha }$$ and the orientation relationship between the main and product crystal structures was Kurdjumov–Sachs type. The dilatation parameter of martensite was calculated to be $$\delta ^{\prime} \cong 0.91$$ . Accordingly, it was found that martensitic phase transformations in the Fe-31.5Ni-10Mn alloy had the isothermal kinetics. Moreover, it was revealed that thermally and deformation-induced martensitic transformations had similar characteristics in terms of morphological and crystallographic aspects.