Geometrical and microstructural characteristics of the TIG-CMT hybrid welding in 6061 aluminum alloy cladding

摘要

A tungsten inert gas (TIG)-cold metal transfer (CMT) hybrid welding process is proposed. Compared with the conventional TIG-metal inert gas/metal active gas (MIG/MAG) hybrid welding method, the characteristic of TIG-CMT welding process is that there is no interaction between the two arcs. The addition of TIG can improve the wettability of molten metal. The microstructure in hybrid joint is coarser than that in conventional CMT joint, and the microhardness in weld metal (WM) of hybrid joint is higher than that of conventional CMT joint. In TIG-CMT hybrid welding process, the TIG current plays an important role in changing contact angle and the dilution of weld bead. Fine equiaxed grains have been observed in partially melted zone (PMZ) and coarsened equiaxed grains exist in heat-affected zone (HAZ). The width of PMZ increases with the increase of heat input. More heat input can also lead to the coarser columnar dendrite. In all weld joints, the microhardness in HAZ remains at a low level, and the microhardness in PMZ always has a sharp decrease from WM to HAZ. The outcome of this work shows that the TIG-CMT hybrid process is suitable for the multi-passes welding of aluminum alloy. (C) 2016 Elsevier B.V. All rights reserved.