A Numerical Simulation for Dissimilar Aluminum Alloys Joined by Friction Stir Welding

• Published in: Metallurgical and materials transactions. A, Physical metallurgy and materials science Vol. 47; no. 9; pp. 4519 - 4529
• Main Authors: Hamilton, Carter, Kopyściański, Mateusz, Węglowska, Aleksandra, Dymek, Stanisław, Pietras, Adam
• Format: Journal Article
• Language: English
• Published: New York Springer US 01-09-2016; Springer Nature B.V
• Subjects: Alloys; Aluminum base alloys; Butt welding; Characterization and Evaluation of Materials; Chemistry and Materials Science; Computer simulation; Cooling; Dissimilar material joining; Friction stir welding; Guinier Preston zone; Hardness; Materials Science; Mathematical models; Metal sheets; Metallic Materials; Nanotechnology; Structural Materials; Surfaces and Interfaces; Temperature distribution; Thin Films; Workpieces; Weld Nugget; Friction Stir Welding; Welding; Weld Zone; Friction Stir Weld
• ISSN: 1073-5623; 1543-1940
• DOI: 10.1007/s11661-016-3617-1

Dissimilar aluminum alloy sheets of 2017A-T451 and 7075-T651 (6 mm thickness) were friction stir welded in a butt weld configuration. A numerical simulation of the joining process was developed to visualize the material flow patterns and temperature distribution and to correlate the microstructure to the hardness behavior. Due to the complementary downward flow of surface material into the workpiece thickness and upward flow of mid-plane and bottom-plane material, the weld nugget is composed of alternating layers of 7075 and 2017A. These layers have unique temperature histories depending on the material’s initial location within the cross section; therefore, they also have distinctive precipitate distributions. Supersaturated surface material flows into the process zone and forms a core in which GP zones reprecipitate upon cooling. Mid-plane and bottom-plane material flow toward the workpiece surface and encompass the surface material core. Within this region, the weld temperatures overage the equilibrium
θ
phase in 2017A, decreasing the hardness, and at the same time, dissolve the equilibrium
η
/
T
phase in the 7075, leading to reprecipitation of GP zones upon cooling and a hardness recovery.