Relationship between crystallographic orientation, microstructure characteristic and mechanical properties in cold-rolled 3.5Mn TRIP steel

Abstract

The relationship between crystallographic orientation, microstructure characteristic and mechanical properties in 3.5Mn transformation induced plasticity (TRIP) steel that subjected to different cold rolling reduction and annealing time was elucidated. Before the hot-rolled plates were cold rolled to different thicknesses, large-fractioned Mn-enriched cementite particles dispersed in ferrite matrix were deliberately prepared to enhance Mn-partitioning and improve austenite stability. The evolution of microstructure was performed by electron probe micro-analyzer (EPMA), electron backscatter diffraction (EBSD), transmission electron microscopy (TEM) and X-ray diffraction (XRD), and the mechanical properties of the intercritical annealed samples were evaluated by uniaxial tensile test at room temperature. The results show that the cementite dissolution, ferrite recrystallization and austenite formation are strongly coupled and interdependent, resulting in a complex ultra-fine microstructure composed of retained austenite, ferrite and cementite in the intercritical annealed samples. Moreover, the Schmid factor (SF) distribution within the range of 0.25–0.5 was studied to understand its correlation with the crystallographic orientation and mechanical property of the test steel. It is concluded that the mechanical properties of 3.5Mn TRIP steel can be improved when the annealing period, orientation and austenite stability are optimized.