Study of abnormal effect of temperature on toughness of an austenitic tensile stainless steel by instrumented impact test

V-notched specimens of an austenitic tensile stainless steer were tested under impact loading in a wide temperature range. Contrary to normal expectation, the impact energy values obtained at low temperatures were found to be much higher than those obtained at higher temperatures. Evidence was obtained previously to show that the improvement of toughness at low temperatures is due to crack-arresting effect of delaminations. Further evidence was produced in the present study to support this hypothesis. In addition, instrumented impact test made it possible to separate initiation energy from propagation energy, and the results in the tests indicate that the initiation energy increased with decreasing temperature. It is argued that the higher initiation energy at lower temperatures also contributes to the "abnormal" effect of temperature on impact toughness.