Predicting dislocation density in martensite ab-initio

The high dislocation density (ρd) in Fe-C and/or Fe-N martensite is known to be one of the main causes its overall yield strength. Experiments indicate that and, therefore, strength low and medium C steels, follows a well defined behavior with respect background concentration (co). In present work, we introduce model based on finding after γ→α′ sufficiently accommodate/trap most available interstitials (C or N) within Cottrell atmospheres. We show number trapped atmospheres scales interaction energy between stress field dislocations C/N misfit tensor. new model, which contains no free fitting parameters, shows as ρd∼c01/4, leading an extremely good match experiments across wide range N concentrations. Therefore, this sheds light mechanistic origin strengthening martensite.