Effect of non-axisymmetric arc on microstructure, texture and properties of variable polarity plasma arc welded 5A06 Al alloy

Highlights: • Variable polarity plasma arc welding of 5A06 Al alloy was carried out under the condition of non-axisymmetric arc. • Deformation bands formed in the weld joint were due to microstructural inhomogeneities. • Tensile fracture occurred along the deformation bands in the TZ/HAZ fusion boundary on the side of "lower arc". • The weld zones are harder than the BM due to dislocation sub-structure, deformation bands and ultrafine subgrain. - Abstract: Microstructure, texture and mechanical properties in the weld joint of variable polarity plasma arc welding of 5A06 Al alloy under the condition of non-axisymmetric arc have been investigated. The weld joint are characterized by elongated structure in the base material (BM), the heat affected zone (HAZ) and the transition zone (TZ) and equiaxed structure in the fusion zone (FZ). Microstructure of the weld joint is asymmetrical and inhomogeneous leading to deformation bands. Deformation texture and recrystallization texture were developed in the weld zones. The FZ center was dynamic recrystallized due to severe deformation. Materials in the TZ have undergone dynamic recovery. The weld zones are harder than the BM due to dislocation sub-structure, deformation bands and ultrafine subgrains. Microhardness distribution was homogeneous in the regions without deformation bands. Tensile fracture occurred along the deformation bands on the side of "lower arc" exhibiting ductile fracture, while the BM is less ductile.