The stress state dependence of dynamic strain aging: Thermal hardening and blue brittleness
14 October 2020
Revised: 31 December 2020
Accepted: 11 January 2021
Available online: 13 January 2021
Abstract: This study aims to discover the stress-state dependence of the dynamic strain aging (DSA) effect on the deformation and fracture behavior of high-strength dual-phase steel at different deformation temperatures (25 °C to 400 °C) and to reveal the damage mechanisms under these various configurations. To achieve different stress states, the pre-designed specimens with different geometry features are employed, and scanning electron microscopy is used to analyze the fracture modes (e.g. dimple or shear mode) and underlying damage mechanism of the investigated material. The DSA is present in this dual-phase steel, showing the Portevin-Le Chatelier (PLC) effect with serrated flow behavior, thermal hardening, and blue brittleness phenomena. It is found that the stress state is contributing distinctly to the DSA effects in terms of both the magnitude of thermal hardening as well as the pattern of blue brittleness. Either lower stress triaxiality or Lode angle parameter is promoting the DSA induced blue brittleness. Accordingly, the damage mechanisms also show dependence on the stress states in conjunction with the DSA effects.