Fig. 1. Schematic of in-situ electrochemical hydrogen charging tensile test

Fig. 2. Microstructure of welded joint. (a) Macroscopic topography; (b) weld zone; (c) coarse-grained region; (d) fine grain zone; (e) incomplete phase transition region; (f) base metal

Fig. 3. Hardness distribution curve of welded joint

Fig. 4. Tensile test results. (a) Tensile engineering stress-strain curves; (b) fracture stress-strain curves under different conditions

Fig. 5. Fracture location. (a) Macroscopic topography; (b) incomplete phase transition zone of fractured sample in air; (c) base material area of fractured sample in air; (d) fracture position of hydrogen-filled sample at current density of 10 mA/cm²; (e) hydrogen embrittlement crack propagation path; (f) morphology of plastic fracture zone

Fig. 6. SEM morphology of fracture surface. (a) Macroscopic appearance of fracture in air; (b) microstructure of fracture in air; (c) macroscopic morphology of in-situ hydrogen filling fracture; (d) morphology of brittle fracture zone of in-situ hydrogen-filled fracture; (e) morphology of in-situ hydrogen filled fracture toughness zone