Tensile deformation behavior of high strength anti-seismic steel with multi-phase microstructure

To investigate the tensile deformation behavior of high strength anti-seismic steel with multi-phase microstructure, tensile tests with strains of 0.05, 0.12 and 0.22 were performed at room temperature. Microstructure of tested steels was observed by means of optical microscopy (OM), transmission electron microscopy (TEM) and scanning electron microscopy (SEM). Tensile mechanical properties of tested steels were obtained, and the influence of bainite content on deformation behavior was also discussed. Meanwhile, the deformation mechanism of steel with three kinds of microstructures of bainite, pearlite and ferrite was analyzed. Results show that tested steel with high volume fraction of bainite exhibits a continuous deformation behavior, and this may be attributed to a higher bainite volume fraction and a lower mobile dislocation density. The morphology of microstructure will influence the mechanical properties of tested steels. An increasing content of bainite can improve the tensile strength, but reduce the plasticity and toughness of the tested steels. In the deformation process of 0.039Nb steel, the ferrite and bainite have priorities to deform, and the deformation exhibits co-deformation of all microstructures in the later stage of deformation. In the deformation process of 0.024Nb-0.032V steel, the ferrite and pearlite have priorities to deform, and the deformation exhibits co-deformation of all microstructures in the later stage of deformation.