TENSILE PROPERTIES OF GAS METAL ARC AND COLD METAL TRANSFERRED ARC WELDED AA6061-T6 ALUMINIUM ALLOY JOINTS

摘要

Heat treatable aluminium alloy such as AA6061 finding wide applications especially in the fabrication of door, hood and trunk components in automobile sector. These components are made up of thin sheets of aluminium alloys due to the low density, high strength to weight ratio, excellent weld ability and better corrosion resistance characteristics. Gas metal arc welding (GMAW) process is one of the most widely used welding technologies in the automobile industry, because of its higher productivity. Cold metal transfer (CMT) welding technique, the most advanced variant of GMAW process attracts the automobile manufacturers because of its capabilities such as stable arc, higher welding speed, less spatter and minimum distortion. This paper focuses on the welding of thin sheets of AA6061-T6 aluminium alloys by constant current-gas metal arc welding (CC-GMAW) and cold metal transfer-gas metal arc welding (CMT-GMAW)processes and highlights its tensile properties. The micro hardness variation across the weld joint was recorded by Vickers micro hardness tester. A soft zone is observed in the HAZ region in both the cases, but the relative softening with respect to the base material is less in case of CMT-GMAW joint compared with the CC-GMAW joint. It is also observed that the width of the soft zone in CMT-GMAW joint is less compared with the CC-GMAW joint. It is concluded that the mechanical properties of CMT-GMAW joint are improved compared with the CC-GMAW joint due to the better refinement of grain structure with narrow soft zone formation.