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.