Dependence of Grain Size on Mechanical Properties and Microstructures of High Manganese Austenitic Steel

A high manganese austenitic steel Fe-25Mn-3Cr-3Al-0.3C-0.01N (in wt. pct) with grain sizes 2.2∼28.7 μm was obtained by annealing the cold rolled sheet at temperature ranging from 700 °C to 1000 °C. Dependence of grain size on the mechanical properties and microstructures of this high manganese steel were studied by using scanning electron microscopy (SEM), transmission electron microscopy (TEM) and room temperature tensile test. The results show that, with the increase of grain size from 2.2 μm to 28.7 μm, the yield and ultimate tensile strengths of this steel were decreased from 410.0 MPa to 232.5 MPa and 725.0 MPa to 517.0 MPa, respectively. And the elongation of this steel was accordingly increased from 15.4% to 54.2%. Additionally, deformation twins are easy to form during tensile deformation when the initial grain size is increased.