Effects of C and N on the high temperature deformation behavior of 15Cr-15Mn-4Ni based austenitic stainless steels

Abstract

Single hit compression tests were carried out at the temperature range of 800~1100 °C and the strain rate range of 0.01~1 s-1 for 15Cr-15Mn-4Ni based austenitic stainless steels containing either 0.1~0.3 wt.% of C or N. The high temperature strength, i.e. mean flow stress, increased as the concentration of either C or N increased. The mean flow stress, activation energy, and degree of lattice distortion of N-added steels were larger than those of C-added steels, while the dynamically recrystallized (DRXed) grain size and grain growth rate were smaller and slower in N-added steels. The effects of N on the high temperature strength were stronger due mainly to a stronger solid solution hardening effect which was attributed to the larger effective size of the N atoms compared to the C atoms. The dynamic recrystallization (DRX) was more suppressed in the N-added steels since N atoms strongly interact with moving dislocations, grain boundaries, or subgrain boundaries, which was evidenced by larger activation energy and peak stress.