Enhanced Mechanical Properties of a Novel High-Nitrogen Cr-Mn-Ni-Si Austenitic Stainless Steel via TWIP/TRIP Effects

摘要

Temperature- and strain-rate-dependent mechanical properties of a high-nitrogen austenitic stainless steel containing smaller amounts of nickel than conventional austenitic nickel-chromium stainless steels were investigated with special attention to the formation of martensite or mechanical twins during plastic deformation (TWIP/TRIP effect). After recrystallization treatment at 1050 °C for 0.5 hour, an equiaxed fully austenitic microstructure possessing annealing twins was observed. Tensile tests were carried out at strain rates ranging from 10?5 to 10?2 s?1 in the temperature range from ?196 °C to 400 °C. Deformation-induced austenite-to-martensite transformation occurred at temperatures below 0 °C. From room temperature up to 200 °C, plastic deformation is controlled by dislocation glide and mechanical twinning. At temperatures above 200 °C, no deformation-induced structural changes were observed. The formations of bcc α′-martensite and hcp ε-martensite, or twins during plastic deformation, were analyzed by optical microscopy, transmission electron microscopy (TEM), and X-ray diffraction.