Effect of process conditions on the evolution of microstructure and mechanical properties of AA3003 vacuum furnace brazing joints

Abstract

In this study, vacuum furnace brazing was used for joining AA3003 alloy with different thicknesses of 0.6 and 3 mm using BALSI-4 filler metal. Firstly, the samples were degreased using water and soap and then cleaned with acetone. The set-up was assembled and pre-heated for two-steps at 235 and 339°C and subsequently, moved to furnace. Vacuum brazing was conducted at temperature range of 590 to 630°C for different holding times of 5 and 10 min followed by furnace cooling. After primary visual checking, three samples for each thickness were selected for evaluation of microstructure and mechanical properties. Results indicated that furnace temperature and holding time significantly influenced microstructural evolution and mechanical properties. This effect was attributed to the distribution of Si and its relevant eutectic and pro-eutectic phases. It was deduced that the amount and distribution of such phases together with joint assembling design controlled the mechanical and fracture behavior. Furthermore, it was found that the quantitative amounts of pro-eutectic Si and Al-Si eutectic phases significantly increased the hardness of the joint. Therefore, the joint brazed at 610°C and dwelling time of 10 min was identified to offer the optimal mechanical properties.

Effect of Post-Weld Heat Treatment on the Solid-State Diffusion Bonding of 6061 Aluminum Alloy

“…The higher tolerance of the process parameter window in brazing comes with the advantage of cost-effectiveness for mass production. However, common filler metals, such as BAlSi-4 and Al-12Si alloys, exhibit high brazing temperatures (above 566 • C) that are close to or above the melting points of some aluminum alloys [10,11], leading to the risk of joint degradation. Some lowtemperature filler metals and the transient liquid phase (TLP) bonding technique have been adopted to address this issue [12,13], and bonding materials such as Cu, Ag, and Mg, which are melting point depressants that form eutectics or intermetallic compounds (IMCs) with Al alloy, have been developed to avoid the risk of melting the base material.…”