Transitions in the strain hardening behaviour of tempered martensite

Martensite is a key constituent in advanced high strength steels (AHSS). The mechanical response of martensite has received particular attention recent years due to its very strain hardening rate. Previous studies have shown that the behaviour as-quenched and low temperature tempered can be described by considering as composite, with constituents showing spectrum yield strengths or residual transformation stresses, more likely, combination both effects. However, composite models are unable explain flow above 400°C when effect starts diminish transition observed. In this contribution, we conduct systematic study on three AHSS compositions. evolution studied using monotonic tension-compression tests while microstructures monitored thermal analysis, interrupted X-ray diffraction microscopy. A continuous loss capacity observed all during tempering at lower temperatures diminishing When 500°C, samples show rates below E/50 limit for dislocation storage gradual increase tempering. To rationalise 600°C, combined isotropic kinematic model back stresses generated cementite particles proposed. need combine work well martensite, dislocation-based discussed context self-consistently describing transitions function temperature.