Effect of welding parameters on diffusion bonding of type 304 stainless steel-copper bimetal

Stainless steel AISI type 304 and electrolytic cold rolled copper were join ed by diffusion bonding at temperatures ranging from 650 to 950 degreesC, f or times from 5 to 45 min, and at pressures from 2 to 12 MPa. After bonding the microstructure of the interface was investigated, including the grain size, and shear and tensile strengths of the bonded specimens were determin ed. From the results, it was seen that the bond shear strength was dependen t on interface grain boundary migration and on grain growth during the bond ing process. In addition, attempts were made to find a relationship between grain size and shear strength in the bonding area. Taking into account the results of shear testing and microstructural observation, for a sound bond , optimum bonding conditions were obtained at temperatures of 800-850 degre esC for 15-20 min at 4-6.5 MPa. The fracture behaviour of the diffusion bon ded joint was investigated by means of shear and tensile testing under diff erent bonding conditions. It was found that both shear and tensile strength s of the bonds were sensitive to the bonding conditions, and the intermetal lic phases did not affect these parameters. Furthermore, the value of shear strength of the bond surface determined by shear testing was higher than t he shear strength of the fracture surface determined by tensile testing. (C ) 2001 IoM Communications Ltd.