Fabrication and Mechanical Properties of Tungsten Inert Gas Welding Ring Welded Joint of 7A05-T6/5A06-O Dissimilar Aluminum Alloy

• Published in: Materials Vol. 11; no. 7; p. 1156
• Main Authors: Wang, Wukun, Cao, Zengqiang, Liu, Kai, Zhang, Xianglong, Zhou, Kewen, Ou, Peng
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 06.07.2018; MDPI
• Subjects: Aging (natural); Alloys; Aluminum alloys; Aluminum base alloys; Backscattering; Base metal; Cylindrical shells; Decomposition; Dislocation density; Dissimilar material joining; Electron diffraction; Elongation; Engineering; Gas tungsten arc welding; Gas welding; Hardness; Heat affected zone; heat input; Inert gas welding; Investigations; Mechanical properties; Microscopy; microstructural characterization; Precipitates; Rare gases; Scanning electron microscopy; similar quenching effect; Softening; Solid solutions; Tensile properties; Tensile strength; Test methods; TIG welding; Transmission electron microscopy; Welded joints; Beijing China; China; microstructural characterization; Aluminum alloys; TIG welding; heat-affected zone; heat input; similar quenching effect
• ISSN: 1996-1944; 1996-1944
• DOI: 10.3390/ma11071156

In this paper, Tungsten Inert Gas Welding (TIG) and single-sided welding and double-sided forming have been used to weld the 7A05-T6/5A06-O dissimilar aluminum alloy circular welded joint of a ring-stiffened closed cylindrical sandwich shell. Microstructural characterization and mechanical properties of welded joints were investigated by use of scanning electron microscopy (SEM), backscatter electron diffraction (EBSD) and transmission electron microscopy (TEM), respectively. Hardness distribution and tensile properties of the welded joints were examined. The results showed the failure of the welded joints produced in the fusion zone (FZ). The tensile strength and yield strength of the welded joints were, respectively, 78.87% and 97.24% of the 5A06-O base metal (BM), and the elongation reached 84.29% of 7A05-T6 base metal. Welding high heat input led to the coarse grain size in the fusion zone, and the long-term similar quenching effect can lead to the full dissolution of the strengthening zone of the fusion zone resulting in the reductions of strength and hardness. Around 7A05 heat-affected zone (HAZ), there is an obvious hardening zone and softening zone, the solid solution precipitates into the Rayleigh brilliant η′ (MgZn₂) phase, which results in natural aging strengthening, thus obtaining high hardness. η′ (MgZn₂) enhanced phase dissolved fully and the dislocation density decreased rapidly in the HAZ region resulted in a softening zone with a lower hardness at about (10⁻18) mm from the center of the weld center.