Numerical simulation and experimental analysis of incomplete fusion mechanism of GH4169 and electroformed Ni electron beam welded joint

•A model for studying the thermoelectric effect in the process of electron beam welding GH4169 and Ni is developed.•The temperature gradient and physical properties together lead to the Seebeck effect.•The distribution laws of current density and magnetic field caused by the thermoelectric effect are obtained.•The deflection of the electron beam caused by the magnetic field is the key factor leading to the lack of fusion defects in the joint.•A defect-free joint is obtained by designing the inclined angle of the joint butt surface. The quality of electron beam welding between GH4169 and electroformed Ni (E-Ni) has emerged as a pivotal factor in the manufacturing of hydrogen-oxygen engines. The welding process involving dissimilar materials, however, is susceptible to the occurrence of incomplete fusion defects, with the underlying causes of these defects remaining elusive. In order to enhance the welding quality of GH4169 and E-Ni and eliminate incomplete fusion defects, a novel finite element model integrating thermo-electro-magnetic multi-physical fields coupling was established in this study, revealing the formation mechanism of such defects. The results demonstrated that significant thermoelectric effects arose during the welding process due to the disparities in temperature gradients and Seebeck coefficients between GH4169 and E-Ni. The thermoelectric effect induces the emergence of a magnetic field, primarily concentrated within a 10 mm zone above the weld. Subsequently, this magnetic field causes a significant deflection of the electron beam towards the GH4169, specifically by 128 µm. This deviation ultimately results in the occurrence of incomplete fusion defects, compromising the welding quality. Based on the underlying mechanism of the thermoelectric effect on the electron beam, an inclined welding joint was designed, successfully eliminating the incomplete fusion defects at the root of the GH4169 and E-Ni electron beam welding joint. The resulting joint exhibited a remarkable strength of 411 MPa. The present analysis of the incomplete fusion defect formation mechanism provides theoretical support for the improvement of the electron beam welding process for GH4169 and E-Ni, pioneering a novel defect-free welding technique for these materials.