Joining of Dissimilar Materials—Aluminium to Steel—Using CMT + P Weld-Brazing Process

Abstract

CMT + P weld-brazing technique was applied for dissimilar joining of aluminium alloy (AA5052) and DP780 steel. Results showed a reduction in wettability of joints on increasing the aluminium (Al) sheet thickness from 1 to 2 mm due to reduced spreading ability of molten filler over steel surface. To overcome the issue of wettability, two approaches were used: (i) increasing WFR and (ii) adding pulses in the weld cycle. A significant improvement in the wettability was observed using both methods. An increase of about 18% (4.8–5.7 kN) and 50% (4.8–7.2 kN) in the load to failure of joints during shear-tensile testing was observed on increasing WFR (5 m/min) and adding two pulses respectively. Spilling of hard and brittle intermetallic phases into fusion zone due to excessive turbulence in the molten pool and formation of geometrical necking resulted in a drop in failure load at WFR of 6 m/min and 4 pulses despite higher wettability at these two parameters. It is suggested to optimize the number of pulses and CMT cycles to improve the load bearing capacity of the joints because in addition to wettability, bead shape and distribution (formation and growth) of intermetallic phases at the interface also play a crucial role in determining the properties of weld-brazed joints. To overcome the issues arising from increased Al sheet thickness, CMT + P technique has the potential to improve the joint properties at a constant deposition rate owing to better control over heat input.