Strain rate and cold rolling dependence of tensile strength and ductility in high nitrogen nickel-free austenitic stainless steel

摘要

The tensile strength and ductility of a high nitrogen nickel-free austenitic stainless steel with solution and cold rolling treatment were investigated by performing tensile tests at different strain rates and at room temperature.The tensile tests demonstrated that this steel exhibits a significant strain rate and cold rolling dependence of the tensile strength and ductility.With the increase of the strain rate from 10-4 S-1 to 1 s-1,the yield strength and ultimate tensile strength increase and the uniform elongation and total elongation decrease.The analysis of the double logarithmic stress-strain curves showed that this steel exhibits a two-stage strain hardening behavior,which can be well examined and analyzed by using the Ludwigson equation.The strain hardening exponents at low and high strain regions (n2 and n1) and the transition strain (eL) decrease with increasing strain rate and the increase of cold rolling RA.Based on the analysis results of the stress-strain curves,the transmission electron microscopy characterization of the microstructure and the scanning electron microscopy observation of the deformation surfaces,the significant strain rate and cold rolling dependence of the strength and ductility of this steel were discussed and connected with the variation in the work hardening and dislocation activity with strain rate and cold rolling.