Effect of pre-consolidated interlayer on the interfacial evolution and mechanical properties of thermo-compensated resistance brazing welded Al/steel joints

Interfacial microstructure and mechanical properties of Al/steel joints with a certain area obtained by resistance seam-assisted thermo-compensated resistance brazing welding, including the pre-consolidation by RSW and the subsequent RBW, with different interlayers were investigated. The results indicated that due to the high melting point of Ni interlayer, the effective connection Al/steel weld was a failure by the single RBW with Ni interlayer or “Ni + Zn” composite interlayers. The pre-metallurgical bonding between interlayer and steel by traditional RSW could obtain a complete Al/steel weld by subsequent RBW. The Al/Ni + Zn/steel joints were obtained successfully and the interfacial structure of the final joints was transformed into as follows: Al alloy, reaction zone, Ni interlayer, and 304ss due to the addition of Zn foil with a low melting point. The main components of the reaction area were Al(s.s) and Al-Ni IMCs. Few Zn element was found at the interface due to the pre-consolidation. The joint performance of the final Al/Ni + Zn/steel joints was the highest and reached 2202.3 N, which was 3.77 times higher than that of the original joint.