Low cycle fatigue behaviour of a nitrogen modified 316L stainless steel at 823 K

Strain controlled low cycle fatigue tests on solution annealed nitrogen modified 316L stainless steel have been conducted in air at 823 K to ascertain the influence of strain rate and strain amplitude. Effect of strain rate was examined from 3x10(-5) s(-1) to 3 x 10(-2) at a fixed strain amplitude of +/- 0.6%. The influence of strain amplitude was evaluated between +/- 0.25 % and +/- 1.0% at a constant strain rate of 3x10(-3) s(-1). The cyclic stress response at all testing conditions is characterized by an initial hardening followed by saturation. Serrated flow, a characteristic feature of dynamic strain ageing (DSA) was seen at strain rates lower than 3x10(-3) s(-1). Fatigue life was found to decrease with decrease in strain rate. The reduction in fatigue resistance is attributed mainly to the detrimental effects associated with DSA.