Joint morphology, characteristics, and role of intermetallics in AA7075 friction stir lap joints with copper interlayer

• Published in: International journal of advanced manufacturing technology 2024-11, Vol.135 (5-6), p.2491-2515
• Main Authors: Kumar, Nikhil, Bhattacharya, Anirban
• Format: Article
• Language: English
• Subjects: Aluminum base alloys; CAE) and Design; Computer-Aided Engineering (CAD; Copper; Engineering; Friction stir welding; Hardness; Industrial and Production Engineering; Interlayers; Intermetallic compounds; Lap joints; Mechanical Engineering; Media Management; Modulus of elasticity; Nanoindentation; Original Article; Process parameters; Rotation; Shear strength; Thickness measurement; Welding parameters
• ISSN: 0268-3768; 1433-3015
• DOI: 10.1007/s00170-024-14663-9

The present work aims to elucidate the effect of process parameters and pin length on microstructure and the characteristics, distribution of intermetallic compounds (IMCs), and associated failure initiation and progress pattern of AA7075 friction stir lap weld (FSLW) joints prepared employing copper interlayer. FSLW joints obtained using various combinations of tool rotation (900 and 1200 rpm), weld speeds (63 and 98 mm/min), and pin lengths (3 mm and 4 mm) are tested for tensile shear strength, fracture behavior, and the influence of IMCs formed are appraised. Further, the elastic modulus and hardness of the IMCs and neighborhood are evaluated using nanoindentation tests to correlate with the joint performance. The non-uniform thickness of AlCu, Al 2 Cu, and Al 4 Cu 9 IMCs is formed due to intermixing of Al and Cu whose thickness varied with process parameters. Higher elastic modulus and hardness are recorded at the IMCs. FSLW joint prepared with 1200 rpm tool rotation, 63 mm/min weld speed, and 4 mm pin length results in better joint formation and higher strength, wherein an IMC layer thickness of around 3–4.3 µm is measured near the hook region.