Effect of varying weld speed on corrosion resistance and mechanical behavior of Aluminium-steel welds fabricated by cold metal transfer technique

Lap welds of 19000 Al-Zinc layered mild steel were joined by Cold Metal Transfer technique using Al-12% Si filler wire as a function of varying weld speed (0.5-1 m.min(-1)). The weld cross-section was characterized by electron microscopy techniques. Micro XRD was used for the phase analysis of the intermetallic layer generated at welding bead-steel interface in the weld samples. The mechanical strength of joints was evaluated by lap shear testing and corrosion evaluation was done following ASTM G 67-04 and ASTM G 48-03, respectively. Results have shown that the IMC layer width decreased with an enhanced welding speed resulting in lower intergranular corrosion. The layer width ranged between 0.45 and 2.3 mu m in both the weld samples. During weight loss evaluation, the sample with lower welding speed exhibited a weight loss of 41.8 mg and the sample welded with higher speed had shown a weight loss of 7.75 mg. At higher weld speeds, lower volume fraction of intermetallics was observed resulting in reduced corrosion. The welds have shown optimum mechanical strength during lap shear test and failed in the base material region of Aluminium alloy.