Effect of Volume Expansion on Transformation Plasticity during Ferrite and Martensite Transformation of Steel

Several kinds of carbon steels and Invar alloys are applied to identify the dependence of transformation volume expansion on transformation plasticity for both diffusive and non-diffusive transformation. It is confirmed by the experiments that the notion of Leblond's model (transformation volume expansion over yield stress of mother phase and transformation plastic coefficient has proportional relationship) appears to be good for both ferrite and martensite transformation. In addition, the experimental results of Invar alloys also support the idea that if the transformation volume expansion is significantly small, the transformation plastic strain becomes small accordingly. It is commonly said that Magee effect (selective martensite variant) plays a main role during martensite transformation. However, for steel treated in this paper, Greenwood-Johnson effect (transformation volume expansion) is also significant for martensite transformation.