Investigation on Non-Equivalence of Dislocation Types on Work Hardening Behavior of Dual-Phase Steel

This work firstly reveals the non-equivalence contribution of geometrically necessary dislocation (GND) and statistically stored dislocation (SSD) to work hardening of the dual-phase steel. The high-GND density of the steel was introduced by load-unload-reload (LUR) pre-tensile, while that with high-SSD density are initiated by monotonic pre-tensile. After pre-deformation, the steel with high GND exhibits significantly higher yield stress and stronger strain hardening ability than the high-SSD steel under almost the same total dislocation density. Different from SSD, GND is originated accompanied by long-range internal stress which can produce additional back stress strengthening. It is further revealed that dislocation hardening produced by GND is stronger in work-hardened metals, and by introducing high-GND density, the strength of the material can be effectively improved in the structure design.