PSI - Issue 68

Vahid Javaheri et al. / Procedia Structural Integrity 68 (2025) 1098–1104 V. Javaheri et. al , Structural Integrity Procedia 00 (2025) 000–000

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Fig. 2. The slow strain tensile test results for both sample with and without hydrogen pre-charging

However, upon hydrogen charging, the mechanical behavior changed drastically. The sample fractured at the very beginning of the plastic deformation region. The UTS decreased by approximately 80 MPa compared to the hydrogen free condition (from 925 MPa to 845 MPa). More significantly, the total elongation suffered a sharp decline, from around 17% to just 2%, underscoring the severe embrittling effect of hydrogen, which drastically reduced the material’s ductility. Figure 3 compares the overall fracture surface of the samples under hydrogen-free and hydrogen-charged conditions. In the absence of hydrogen, the fracture surface exhibits characteristics typical of ductile failure, characterized by a network of deep and shallow dimples, along with shear lips near the edges of the fracture. The dominant failure mechanism in this condition is micro-void coalescence (MVC), indicating that the material underwent significant plastic deformation before failure.

Fig. 3. The fracture surface of a) not pre-charged sample and b) pre-charged sample by H2