Carbon diffusivity and kinetics of spinodal decomposition of martensite in a model Fe-Ni-C alloy

International audienceFrom direct observations and measurements at the atomic scale by atom probe tomography coupled with calculations using a mean-field approach, the kinetics of low temperature carbon redistribution in martensite of a Fe-Ni-C alloy was investigated for duration up to 4.5 years. The results suggest that the ordered phase α″-Fe16C2 forms via a spinodal decomposition mechanism, in the range of a few days at room-temperature. The approach proposed allows us to retrieve the diffusivity of carbon in a large composition range during decomposition kinetics of martensite into α-Fe and α″-Fe16C2