New investigations on transformation induced plasticity and its interaction with classical plasticity

In this paper, transformation induced plasticity (TRIP) in anisothermal single as well as double transformations (austenite → bainite and austenite → bainite + Martensite) in 16MND5 steel is experimentally analyzed. Several investigations have been performed related mainly on: (a) the evaluation of the physical mechanism responsible of the TRIP in bainitic transformation; (b) the kinetics of TRIP and its specificity in a double transformation; (c) the consequence when the load is applied during only a part of phase transformation; (d) the interaction between TRIP and classical plasticity and so on. The results seem indicate that Greenwood and Johnson mechanism is dominant compared to Magee mechanism. The interaction between classical plasticity and TRIP is clearly demonstrated and it seems that the strain hardening state of the parent phase plays an important role in the TRIP progress. Due to such interaction, TRIP appears even in the absence of external applied load; the behavior depends strongly on the transformation under consideration (bainitic or martensitic). From a modeling point of view, it is shown that Leblond’s model that is the only one “industrial” model which enables qualitatively to account for such interactions, fails to predict the observed phenomena especially in martensitic transformation.