Abstract
Various heat input conditions and post-weld heat treatments were adopted to investigate the microstructure evolution and mechanical properties of tungsten inert gas (TIG) welded joints of AA6082-T6 with porosity defects. The results show that the fracture location is uncertain when an as-welded joint has porosities in the weld zone (WZ), and overaging in the heat-affected zone (HAZ) at the same time. When the fracture of the as-welded joint occurs in the HAZ, the total heat input has a linear relation with the tensile strength of the joint. An excess heat input induces the overgrowth of Mg2Si precipitates in HAZ and the coarsening of α-Al grains in WZ, resulting in a decrease in the microhardness of the corresponding areas. After artificial aging treatment, the tensile strength of the welded joint is increased by approximately 9–13% as compared to that of as-welded joint, and fracture also occurs in HAZ. In contrast, for solution treated and artificial aging treated joint, fracture occurs suddenly at the rising phase of the tensile curve due to porosity defects throughout the weld metal. Furthermore, the eutectic Si particles of WZ coarsen and spheroidize after solution treatment and artificial aging treatment, due to the diffusion of Si to the surface of the original Si phases when soaking at high temperature.
Highlights
The 6XXX series aluminum alloys have been used extensively in the aeronautical, maritime, and ground transportation industries, due to their moderate strength, outstanding weldability, and excellent corrosion resistance [1]
It was more likely to occur in heat-affected zone (HAZ) and could possibly occur in weld zone (WZ)
Fracture was more likely to occur in HAZ
Summary
The 6XXX series aluminum alloys have been used extensively in the aeronautical, maritime, and ground transportation industries, due to their moderate strength, outstanding weldability, and excellent corrosion resistance [1]. The mechanical properties of such alloys can even be enhanced by solution treatment and artificial or natural aging. Due to these properties, the alloys have served as one of the most important aluminum alloy structural materials in the field of welding. The welding technology of 6XXX series aluminum alloys is a key process that affects the wide application of the alloys. Welding 6XXX aluminum alloys by tungsten inert gas (TIG). Due to the intrinsic problem of overaging in heat-affected zone (HAZ) [2] and hydrogen porosity in aluminum welding [3], it remains a great challenge for designers and technologists to join 6XXX aluminum alloys by fusion welding
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