Effects of Ti Addition into Core Alloy on Forming and Brazing Characteristics of 4343/3003/4343 Aluminum Alloy Clad Sheets

Abstract

The effects of Ti addition into a 3003 core alloy on the cold press forming and brazing properties of 4343/3003/4343 aluminum clad sheets were investigated. 3003 alloys with various Ti addition levels (0, 0.02 and 0.16 mass%) were prepared by adding with an Al–10 mass%Ti master alloy; these alloys were then fabricated into three-layer clad sheets by a roll-bonding process. The addition of a small amount of Ti into the 3003 core alloy at the initial casting stage had a large effect on the grain structure and microstructure of the core layer (after stress relief annealing) and the filler layer (after brazing), as well as on the grain structure in the as-cast state. The cold-forming characteristics of the clad sheets strongly depended on the recrystallization and grain growth behavior of the 3003 core layer during stress relief annealing at different Ti addition levels. Moreover, Ti addition increased the press formability of the clad sheets at room temperature by twofold or more. A coarse microstructure of the resolidified filler layer due to slow cooling during the brazing process was observed to cause intergranular cracking in the filler layer of the clad sheets. For this reason, significant Ti migration from the core layer to the clad layer improved the brazing strength of the clad sheets, refining the microstructure of the resolidified filler layer. Further, sagging resistance during the brazing process was also improved upon increasing the Ti level.