Experimental results on classical plasticity of steels subjected to structural transformations

This work deals with the analyses of the behavior of a 16MND5 steel (French norm) subjected to temperature variations, which generate solid–solid metallurgical structural changes. Two mechanical phenomena related to phase transformations are particularly studied: the possible recovery of strain hardening of the parent phase and the classical elastoplastic behavior of mixtures composed of two different phases. These phenomena are analyzed considering two phase transformations: austenite→bainite and austenite→martensite. Contrary to the martensitic phase, the bainitic one, seems inherit a large part of the austenitic strain hardening. The obtained results show that a simple linear mixture rule enables satisfactory description of the behavior of the mixtures martensite–bainite while a non linear mixture rule (parabolic) is necessary to represent the behavior of austenite–martensite and austenite–bainite mixtures. This last result confirms the theoretical and numerical micromechanical studies performed by Leblond et al. 15 years ago [J. Mech. Phys. Solids 34 (1986) 395 and 411].