Study on uniaxial tensile deformation of bainite/ferrite dual phase steel

Abstract

The microstructure evolution of a ferrite/bainite dual-phase steel during uniaxial tension was observed in-situ technology. The effects of tensile rates on microstructure, mechanical properties and fracture mechanism were studied. The result shows that stress concentration is easy to form cracks at the interfaces between ferrite and bainite. The sample exhibits high uniform elongation and strength at low-strain rate, which is attributed to the effective interaction between dislocations. The microstructure undergoes orderly and continuous high hardening rate under ‘harmonious’ conditions. Dislocations are rapidly entangled at high-strain rate and dislocation cells forms. The increased strength of the ferrite brings a reduction in its ability to coordinate more plastic deformation, which eventually leads to local plastic instability and early fracture.