J-integral Fracture Toughness of High-Mn Steels at Room and Cryogenic Temperatures

Abstract

The J-integral fracture toughness values of high-Mn steel (Fe-25 wtpct Mn) and 304L stainless steel were evaluated at 25 degrees C, 0 degrees C, -50 degrees C, -100 degrees C, -163 degrees C, and -196 degrees C using precracked compact tension (CT) specimens and compared to those determined using Charpy impact tests. The high-Mn steel exhibited excellent J-integral fracture toughness at both room and cryogenic temperatures, with values comparable to those of 304L stainless steel. However, the trend of the J-integral fracture toughness of high-Mn steel with the decreasing temperature differed from that of the Charpy impact test results. Electron backscattered diffraction and micrographic analyses suggest that the varying stacking fault energies of high-Mn steels at different temperatures affected the deformation behavior in the stretch zone at the crack tip of the CT specimen. The effect of this temperature-dependent deformation behavior of high-Mn steels on the fracture process in the J-integral test could differ from that in the Charpy impact test, resulting in the different trends in the fracture resistance with the decreasing temperature. (C) The Minerals, Metals & Materials Society and ASM International 2019