The tensile and low-cycle fatigue behavior of cold worked 316L stainless steel: influence of dynamic strain aging

Abstract

Tensile and low-cycle fatigue (LCF) tests were carried out in air in a wide temperature range from 20 to 750 °C and strain rates of 1×10 −4–1×10 −2/s to investigate the influence of strain rate on tensile and LCF properties of cold worked 316L stainless steel, especially in the dynamic strain aging (DSA) regime. Dynamic strain aging caused a change in the tensile properties such as strength and ductility in the temperature range from 250 to 600 °C. This temperature range coincided well with the regime of negative strain rate sensitivity. Cyclic stress response at all test conditions was characterized by an initial hardening during the few cycles, followed by gradual softening until failure. Temperature and strain rate dependence on cyclic softening appears to come from a change of the cyclic plastic deformation mechanism and the DSA effect. The regimes of DSA between tensile and LCF loading conditions in terms of the negative strain rate sensitivity were consistent with each other. At the elevated temperature, a drastic reduction in fatigue resistance was observed, and this is attributed to the effects of oxidation, creep, and dynamic strain aging and interactions among these factors. The regime of DSA accelerated a reduction in fatigue resistance by enhancing crack initiation and propagation.