Dynamic strain ageing effects on superduplex stainless steels at intermediate temperatures

The mechanical response under monotonic conditions of a superduplex stainless steel (SDSS) at intermediate temperatures was studied. Tensile tests were performed at temperatures ranging from 275 to 475 °C, paying special attention to the evolution of mechanical properties, strain rate sensitivity and serrated flow, factors that indicate the occurrence of dynamic strain ageing (DSA). In order to evaluate the influence of strain rate on this phenomenon, tensile tests were conducted at two different strain rates, both at 325 °C, because it was found out that DSA reaches its maximum effect around this temperature. In addition, compression tests were done with the objective of determining the activation energy for solute diffusion and therefore the mechanisms of DSA in this two-phase alloy. The results confirm the existence of DSA in the steel being investigated and seem to point out that it is mainly due to diffusion of chromium atoms in the ferritic phase.