Kinetics of deformation martensite formation in TRIP/transformation induced plasticity/steels

The kinetics in carbon and nitrogen alloyed austenite unstable steels are studied during formation of deformation martensite. The experimental results are interpreted from the view point of M.Cohen theory of deformation martensite formation. An assessment is made for the effect of the alloying elements on these processes. The ɛ-martensite formation kinetics is typical for the non-diffusion transformations, with no presence of incubation period. The α-martensite formation is characterized by incubation period at degrees of plastic deformation of the order of 3-5% after which at higher deformation degrees their growth is stimulated. The nitrogen alloys the increase of the martensite quantity is in much narrower deformation limits compared to these of carbon martensite connected with lower stacking faults energy (SFE). Chromium increases the nucleation activation energy and simultaneously decreases the nuclei critical size which results in favoring the processes of deformation martensite formation.