Improvement in Diffusion-Bondability of A6061 Aluminum Alloy to SUS316 Stainless Steel using Ag Insert Metal and Its Quantitatively Evaluation by Mathematical Method

Study on Diffusion Bonding of Aluminum Alloy to Stainless Steel (Report 2)

Abstract

The diffusion-bondability of A6061 aluminum alloy to SUS316 stainless steel was improved by using Ag insert metal. Diffusion bonding of A6061/SUS316 was carried out at 758-848 K for 0.3-12.0 ks applying 9.8 MPa in vacuum. Ag insert metal was electroplated on SUS316 stainless steel following the uderplating of Ni prior to diffusion bonding. The thickness of Ag insert metal was varied between 0.5 and 3μm. The contour maps of joint strength were obtained through the mathematical calculation by using interpolation method. The maximum joint strength of 130 MPa was presumed when the thickness of Ag insert metal was 1μm and the bonding condition was 795 K×1.0 ks. The safety margins of bonding conditions where the sound joint strength was maintained were clearly enlarged by using Ag insert metal compared with direct-diffusion bonding, although the maximum value of joint strength became slightly below that in direct-bonding. Microstructural analyses revealed that the reaction layer consisted of Al-Ni and/or Fe-Al intermetallic compounds were formed at the A6061/SUS316 interface, and that Ag insert metal mostly diffused away into A6061 base metal at the optimum bonding condition.