• The base metal (BM) had a lower critical stress intensity factor (KⅠSCC = 7.05 MPa·m1/2) than the weld zone (WZ = 11.79 MPa·m1/2), indicating higher SCC susceptibility in the BM.
• Crack propagation was faster in the BM than in the WZ, with BM exhibiting transgranular fracture and WZ showing a mixed intergranular/transgranular fracture mode.
• The SCC mechanism is governed by the synergistic effects of anodic dissolution and hydrogen embrittlement, providing a scientific basis for predicting and mitigating SCC in welded aerospace components.
• This research supplies crucial experimental evidence and theoretical support for the safe and reliable application of TIG welded Al-Mg-Mn-Sc-Zr alloys in the aerospace industry.