Interplay between temperature-dependent strengthening mechanisms and mechanical stability in high-performance austenitic stainless steels

The effects of deformation temperature on the transformation-induced plasticity (TRIP)-aided 304L, twinning-induced plasticity (TWIP)-assisted 316L, and highly-alloyed stable 904L austenitic stainless steels were compared for the first time to tune the mechanical properties, strengthening mechanisms, and strength-ductility synergy. For this purpose, the scanning electron microscopy (SEM), electron backscattered diffraction (EBSD), X-ray diffraction (XRD), tensile testing, work-hardening analysis, and thermodynamics calculations were used. The induced plasticity effects led to a high temperature-dependency of work-hardening behavior in the 304L and 316L stainless steels. As the deformation temperature increased, the metastable 304L stainless steel showed the sequence of TRIP, TWIP, and weakening of the induced plasticity mechanisms; while the disappearance of the TWIP effect in the 316L stainless steel was also observed. However, the solid-solution strengthening in the 904L superaustenitic stainless steel maintained the tensile properties over a wide temperature range, surpassing the performance of 304L and 316L stainless steels. In this regard, the dependency of the total elongation on the deformation temperature was less pronounced for the 904L alloy due to the absence of additional plasticity mechanisms. These results revealed the importance of solid-solution strengthening and the associated high friction stress for superior mechanical behavior over a wide temperature range.