Microstructure and mechanical properties of electron beam welded alloy J75 were studied under as-welded and post-weld aging treatment(PWAT)conditions.The results showed that high-quality welds were produced by electron beam welding.Under as-welded condition,a fine dendritic structure consisting of gamma dendrite matrix and Laves phase was observed in the welds.Better mechanical properties were obtained in the weld zone than that of base metal because of the fine size of the dendritic structure.After PWAT,a discontinuous distribution ofγ’particles existed in the dendritic structure.The presence of aγ’depletion zone in the dendrite core resulted in a significant degradation of mechanical properties of the weld. Microstructure and mechanical properties of electron beam welded alloy J75 were studied under as-welded and post-weld aging treatment (PWAT) conditions. The results showed that high-quality welds were produced by electron beam welding. Under as-welded condition, a fine dendritic structure consisting of gamma dendrite matrix and Laves phase was observed in the welds.Better mechanical properties were obtained in the weld zone than that of base metal because of the fine size of the dendritic structure. After PWAT, a discontinuous distribution of γ’particles existed in the dendritic structure. The presence of a gamma depletion zone in the dendrite core resulted in a significant degradation of mechanical properties of the weld.