Temperature-jump tensile tests to induce optimized TRIP/TWIP effect in a metastable austenitic stainless steel

In the present work, plastic deformation mechanisms were initially tailored by adjusting the deformation temperature in the range of 0 to 200 °C in an AISI 304L austenitic stainless steel, aiming to optimize the strength-ductility synergy. It was shown that the combined twinning-induced plasticity (TWIP)/transformation-induced plasticity (TRIP) effects and a wider strain range for the TRIP effect up to higher strains by adjusting the deformation temperature are good strategies to improve the strength-ductility synergy of this metastable stainless steel. In this regard, by consideration of the observed temperature-dependency of plastic deformation, the controlled sequence of TWIP and TRIP effects for archiving superior strength-ductility trade-off was intended by the pre-designed temperature jump tensile tests. Accordingly, the optimum tensile toughness of 846 MJ/m3 and total elongation to 133% were obtained by this strategy via exploiting the advantages of the TWIP effect at 100 °C and the TRIP effect at 25 °C at the later stages of the straining. Consequently, a deformation-temperature-transformation (DTT) diagram was developed for this metastable alloy. Moreover, based on work-hardening analysis, it was found that the main phenomenon constraining further improvement in the ductility and strengthening was the yielding of the deformation-induced α΄-martensite.