Experimental analysis and modelling of Fe-Mn-Al-C duplex steel mechanical behaviour

A new variety of duplex steels with high content of manganese and aluminum has been elaborated in Arcelor Research. These steels contain two phases: austenite and ferrite combining the best features of austenitic and ferritic steels. In this work four duplex steels with different chemical composition and phase volume fraction are studied. The evolution of internal stresses for the two phases has been determined by X-ray diffraction during an in situ tensile test. These measurements results were used to determine the mechanical behaviour of the duplex steel using a micromechanical approach by scale transition for tensile tests. Though a good agreement between experiments and simulations is found at the macroscopic level, the calculated internal stresses of the austenitic phase do not match experimental results. These discrepancies are attributed to (i) a bad estimation of the austenite yield stress or (ii) the presence of kinematic hardening in the austenitic phase. A new step is then proposed to test these two hypotheses.