Welding of aluminium by the MIG process with indirect electric arc (MIG-IEA)

A novel modification of the metal inert gas (MIG) welding method, which was developed to weld metal matrix composites, was applied to join plates of aluminium 12.5 mm thick. The plates were prepared with square edges and with a small single-V preparation with an angle of 45 in the upper part. The electric arc was indirectly applied on the single-V butt weld over strips of Al- 2024 placed on top of the joint. Thermal analysis showed that the efficiency of the MIG process with indirect electric arc (IEA) is increased due to the reduction of heat losses and fully penetrated welds with a high depth-to-width ratio can be produced as compared to plain MIG welding in which partial penetration and lack of lateral fusion were observed. Microstructural examination of the welds revealed distinct characteristics such as partially melted grains trapped within the weld next to the fusion line for IEA welds and the typical epitaxial and columnar growth from the base metal partially melted grains for plain welds, i.e. direct application of the electric arc (DEA).