中间层对铜/钢扩散焊焊接接头组织和性能的影响

The mechanism of diffusion bonding between martensitic stainless steel 00Cr12Nil0MoTi and a novel copper alloy Cu3Crl. 5Nb using Ni foil and AgCu37.5 as interlayers is investigated. Vacuum diffusion bonding was conducted at 980 C for 90 min under a pressure of 5 MPa. The microstructures and mechanical properties of the joints were systematically characterized by optical microscopy, scanning electron microscopy, X-ray diffraction, and tensile test. The results indicate that all three types of joints achieved interfacial metallurgical bonding to varying degrees. The direct diffusion-bonded joint exhibited a discontinuous interface with a tensile strength of 476. 36 MPa and a dimpled fracture surface characteristic of ductile failure. In the joint with the AgCu37.5 interlayer. Ag diffused toward the Cu side and segregated along the grain boundaries of the steel substrate resulting in microcracks and Kirkendall voids due to the wetting and spreading of the filler metal. This joint fractured within the weld zone under tension showing a tensile strength of 479. 61 MPa corresponding to a 0.7% increase, and a mixed ductile-brittle fracture mode. In contrast, the joint with the Ni foil interlayer demonstrated excellent metallurgical bonding on both sides, forming ductile solid solutions, Cr, Ni, intermetallic compounds and Kirkendall voids. It achieved a tensile strength of 491.38 MPa representing a 3.1% improvement and fractured in the copper substrate with clear dimples, indicating ductile fracture. Therefore, the use of a Ni foil interlayer enables sufficient interfacial bonding and superior joint performance in the diffusion bonding of stainless steel to copper alloy.