Material characterization,crystallographic texture,and mechanical performance of friction stir welded aerospace-grade dissimilar aluminum alloys

Abstract

Friction Stir Welding (FSW) is highly effective for joining aluminum alloys, including difficult-to-weld 2xxx and 7xxx series. This study examines FSW of dissimilar AA2014 (advancing side) and AA7075 (retreating side) using weld codes AW5, AW6, AW7, and AW8 at welding speeds of 20–50 mm/min with a T2 tool profile (SD:PD = 16:4). The AW5 stir zone (SZ) exhibited a fine-grained structure (2.03 µm ± 1.46) with 42.74% High-Angle Grain Boundaries (HAGBs), compared to 15.03% in AA2014 base metal. Grain refinement resulted from Severe Plastic Deformation (SPD) and frictional effects. The crystallographic texture revealed pronounced shear components, including A1*/A2* (shear bands on {111} <110>), A/ $\overline{\mathrm{A}}$ and B/ $\overline{\mathrm{B}}$ (ideal FSW shear components), and a slight C component, confirming effective material flow and high shear strain. Additional Cube, S, and H components at φ₂ = 65° indicated concurrent deformation, recovery, and recrystallization. AW5 achieved superior mechanical properties, with hardness improvements of 16%, 25%, and 18% in RS-BM, SZ, and AS-BM, respectively, compared to AW6. It also exhibited higher Ultimate Tensile Strength (319 MPa), Yield Strength (235 MPa), and Elongation (10.28%). Flexural strength increased by 93%, 70%, and 65% for AW5, AW8, and AW7, respectively, compared to AW6, with AW5 attaining a maximum joint efficiency of 91%.