Effect of Cold Deformation on Microstructure and Mechanical Properties of a Fe-20Mn-19Cr-0.5C-0.6N High Nitrogen Austenitic Steel

The effect of cold deformation on microstructure and mechanical properties of a Fe–20Mn–19Cr–0.5C–0.6N high nitrogen austenitic steel has been studied. Microstructural observations show that the low cold deformation is fully dominated by the dislocation structures, namely, pile-ups, Taylor lattice, and dislocation cells. With further cold deformation, the effect of twinning induced plasticity and grains fragmentation play an important role during cold deformation process. At critical cold deformation reduction range of 26–36%, the microstructural transitions by dislocation planar slip and multiplication gradually transits to twinning. For mechanical properties, with the increase of cold deformation reduction, the yield strength increases from 0.52 to 1.60 GPa, being increased by three times. The flow stress–strain model of the solution-treated specimen can be described as σ = 1974 ϵ 0.402 + e − 0.3625 ⋅ e − 33.114 ϵ . In addition, the strength-elongation product and the cold deformation reduction present a linear relationship with a correlation coefficient of −0.27 to estimate the variation rate of the strength-elongation product during cold deformation.