Study of the processing map and hot deformation behavior of a Cu-bearing 317LN austenitic stainless steel

The hot-working behavior of a Cu-bearing 317LN austenitic stainless steel (317LN-Cu) was investigated in the 950-1150 degrees C temperature and 0.01-10 s(-1) strain rate range, respectively. The effects of different deformation parameters and optimum hot-working window were respectively characterized through analyzing flow stress curves, constitutive equations, processing maps and microstructures. The critical strain for dynamic recrystallization (DRX) was determined by the inflection point on theta-sigma and -partial derivative theta/partial derivative sigma-sigma curves. The peak stress was found to increase with decrease in temperature and increase in strain rate. Typical signs of DRX over a wide range of temperatures and strain rates were observed on the flow stress curves. The power dissipation maps in the strain range of 0.1-0.4 were basically similar, indicating the insignificant effect of strain on the power dissipation maps of 317LN-Cu. However, the instability maps showed strong strain sensitivity with increasing strain, which was attributed to the flow localization. The optimum hot-working window for 317L14-Cu was obtained in the temperature range 1100-1120 degrees C and strain rate range 0.01-0.018 s(-1), with a peak efficiency of 38%. Microstructural analysis revealed fine and homogenized recrystallized grains in this domain. (C) 2015 Elsevier Ltd. All rights reserved.