Experimental analysis of the correlation between martensitic transformation plasticity and the austenitic grain size in steels

This work investigates the effect of the Austenite Grain Size (AGS) on the thermo-mechanical behavior of 35NiCrMo16 steel during the martensitic transformation under complex loading. Particularly in view of some thermal cycles, we analyzed the evolution of the austenite grain size under different austenitizing conditions. Using the same temperature-holding time parameters, we performed a series of experiments to assess the Transformation-Induced Plasticity (TRIP) under uniaxial (tension or torsion) and biaxial (tension + torsion) loading. The results suggest that the uniaxial torsion loading case, Transformation-Induced Plasticity does not depend on the prior Austenite Grain Size (AGS) whereas, in the uniaxial tension loading case, it is a “slightly” increasing function of the AGS.