Impact toughness properties of nickel-free austenitic stainless steels

The Charpy-V impact toughness of six interstitially-alloyed nickel-free austenitic stainless steels was investigated in the temperature range between −196 and 150 °C. Unlike traditional face-centered-cubic steels, the investigated alloys show a marked decrease in impact toughness with decreasing temperature and cleavage-like fracture surfaces at low temperatures. The decrease in impact toughness is due to the combined effects of high strain rate and temperature sensitivity of plastic flow and the strong planarity of the deformation mechanisms of nitrogen-alloyed nickel-free alloys at low temperatures. The effects of the high strain rate and temperature sensitivity of the flow stress on the fracture behavior are discussed based on an analysis of the critical stress for fracture and plastic flow.