Weld-Solidified Structure of Commercial 5083 Aluminum Alloy and its Mechanical Behavior

Abstract

Experiments were conducted to study the structural features of weld-solidified metal in commercial 5083 aluminum alloy and its influence on the fracture behaviors.
The shape of weld bead was considerably influenced by welding variables and heat input. In these behaviors, height of reinforcement was influenced by the heat input but depth of penetration was done mainly by the welding current, while width of bead depended on the both of them.
Structures of common 5083 alloy welds containing no refining elements consisted of fine columnar, coarse columnar, granular and feather grains. In these structures, the volume fractions of fine columnar and feather grains were increased with heat input but those of coarse columnar and granular grains were decreased reversely. The width of columnar grain had a tendency to increase with heat input. On the other hand, 5083 alloy welds containing small amounts of Ti-B showed the fine granular structure all over the fusion zone.
When weld metals having fine columnar, coarse columnar and granular grains were stretched, crack occurred preferentially at the grain boundary of coarse columnar structure. In weld metals having taining feather grains, however, it was important to consider the relationship between the growth direction of feather grain and the stretching direction. Crack occurred preferentially at feather grain when stretched transversely to growth direction of feather grain but it did not occur in this way when stretched parallelly.