RESISTANCE SPOT WELDING OF DISSIMILAR METALS AISI 1006 LOW CARBON STEEL AND AA6061 ALUMINUM ALLOY USING ZINC AND TIN COATING

Abstract

In this research, low carbon steel (AISI 1006) and aluminum (AA6061) were joined by resistance spot welding. Different types of coating for the base metals were used to examine their influence on the properties of the welded joint. A tensile shear test for the welded joints was performed to determine the best welding conditions. low welding current produced an interfacial failure mode, and the failure mode changed from interfacial to partial pullout and full pullout failure modes with increasing welding current. For the as-welded joints, the best welding condition was 6 kA, 0.6 s, and the joint recorded a shear force of 2.7 kN. The shear force increased to 4.24 kN for the tin-coated steel / zinc-coated aluminum joint. The microstructure examination showed the welding made through a brazing mechanism. However, the existence of the Fe-Al intermetallic compound (IMC) caused a cracking at the joint interface. The microhardness of the joint was affected by the heat of welding and varied across the joint. An increase in the microhardness of aluminum in the weld nugget occurred because of the IMC.