Lattice Defects Present beneath Crack Initiation, Propagation, and Final Fracture Regions on the Same Hydrogen Embrittlement Fracture Surface of Martensitic Steel

Atomic-scale lattice defects beneath various hydrogen embrittlement fracture process regions, i.e., different fracture modes, were compared for martensitic steel. The crack initiation region containing quasi-cleavage (QC) and intergranular (IG) fracture, the crack propagation region mostly consisting of IG fracture, and the final fracture region completely composed of microvoid coalescence (MVC) were extracted from the same fracture surface and analyzed by low-temperature thermal desorption spectroscopy (L-TDS). The relative shapes of the L-TDS curves were different at the sampling positions, demonstrating at the atomic-scale that the types and numbers of lattice defects formed vary depending on the fracture process and fracture mode.