Investigation of Tensile and Impact Properties Associated with Microstructures of a Cast Austenitic High-Manganese Steel and CF3 Austenitic Stainless Steel for Cryogenic Application

The tensile and impact properties of the cast austenitic high-Mn steel (HMBASE alloy) and CF3 cast austenitic stainless steel (CF3 alloy) were compared to their microstructures using OM, EBSD, FESEM-EDS, XRD, and martensite measurement via feritscope. The HMBASE alloy demonstrated superior tensile properties, with yield and tensile strengths 1.31 and 1.28 times higher than the CF3 alloy. Despite 5% lower elongation, the HMBASE alloy still achieved 58% elongation. After the cryogenic impact testing at - 196 degrees C, the HMBASE alloy's alpha'-martensite content increased marginally from 0 wt. to 0.29 wt.% due to the TWIP effect. Conversely, the CF3 alloy's alpha'-martensite content increased substantially from 44.5 wt. to 58 wt.%, attributed to the TRIP effect compared with the results after the tensile test at room temperature. The HMBASE alloy exhibited absorbed impact energy comparable to the CF3 alloy, despite higher yield and tensile strengths. The enhanced strength, ductility, and impact toughness of the HMBASE alloy with 25.2 mJ/m2 SFE resulted from the interstitial solid solution strengthening effect by high C of 0.44 wt.% and Hall-Petch-type strengthening from numerous twin grain boundaries and fine twin grains formed via TWIP mechanism during the tensile and impact deformations, compared with the CF3 alloy with 16.2 mJ/m2 SFE containing low C of 0.02 wt.%.