Electron beam welding of Nb/GH3128 dissimilar alloys was conducted in this research. Microstructure characterization and finite element simulation were utilized to uncover the cracking mechanism of the joint. The obtained results revealed that a brittle reaction layer, composed of Ni₆Nb₇/Laves phase beside the Nb substrate, was a critical cracking factor triggering the cracking along the reaction layer. The generation of cracks was affected by a certain thermal-mechanical effect. The longitudinal residual stress fluctuated dramatically in the Nb/FZ interface region, resulting in different welding deformation. High transverse residual stress was also detected in the vicinity of Nb/FZ interface, increasing the cracking propensity of Nb/GH3128 joint. This high residual stress combined with the brittle reaction layer illustrated the intrinsic cause of welding crack. Crack-free welding of Nb/GH3128 dissimilar alloys was realized via adopting the beam offset process. The thickness of the brittle reaction layer was dramatically decreased and the brittle Laves phase within FZ was replaced by the γ phase.

本研究进行了 Nb/GH3128 异种合金的电子束焊接。微观结构表征和有限元模拟被用来揭示接头的开裂机制。所得结果表明，由 Ni ₆ Nb ₇组成的脆性反应层Nb 衬底旁边的 /Laves 相是触发沿反应层开裂的关键开裂因素。裂纹的产生受一定的热机械效应影响。Nb/FZ界面区域纵向残余应力波动剧烈，导致焊接变形不同。在 Nb/FZ 界面附近也检测到高横向残余应力，增加了 Nb/GH3128 接头的开裂倾向。这种高残余应力与脆性反应层相结合说明了焊接裂纹的内在原因。采用束偏移工艺实现了Nb/GH3128异种合金的无裂纹焊接。脆性反应层的厚度显着降低，FZ内脆性Laves相被γ相取代。