Study on crack generation mechanism of GH4251 vacuum electron beam welding joint

The present study investigates the microstructural evolution and mechanical properties of a GH4251 vacuum electron beam welding (VEBW) joint. It aims to elucidate the mechanisms underlying internal crack formation and to identify the factors influencing the tensile strength of the joint at room temperature. The findings provide a theoretical foundation for optimizing subsequent processing techniques for this material. The microstructure of the weld zone (WZ) in the joint has been characterized, revealing secondary microscopic components including the γ′ phase, TiC carbide, M₃B₂, γ/γ′ eutectic, and γ/MC eutectic. The mechanism underlying the formation of inter-dendritic solidification cracking in the WZ has been elucidated. When the combined shrinkage stress and residual stress in the welded joint exceed the tensile strength of the liquid film, the liquid film tears. If the liquid film cannot fully backfill the torn area, a solidification cracking forms. Based on the mechanisms of solidification cracking and MC carbide fragmentation, the key factors influencing the tensile strength of GH4251 VEBW joints at room temperature have been identified.