A parametric study of interlayer incorporated friction stir welded Al/Cu and its effect on microstructure and mechanical properties

PARAMETRIC STUDY OF FS WED AL/CU JOINTS WITH INTERLAYER

Abstract

This study examines the influence of various parameters on the microstructural and mechanical characteristics of friction stir-welded 3 mm thick AA6101/C11000 dissimilar joints with a hybrid interlayer consisting of Ag and Zn. Using scanning electron microscopy and energy-dispersive X-ray spectroscopy, this study provides valuable insights into the microstructural examination of joints. This study identified the optimal weld parameters to achieve a sound weld with good mechanical properties in AA6101/C11000 joints. As there was a lack of optimal weld parameters for the friction stir welding of AA6101/C11000 joints using the interlayer approach, the study carefully derived the optimal weld parameters for achieving sound welds and optimal mechanical properties. The study found that different traverse speeds (0.75 mm/s, 1.25 mm/s, 2.25 mm/s) had varying tensile strengths, which were influenced by the thickness and brittleness of the intermetallic layer. The rotational speed, ranging from 800 to 1800 rpm, also had an impact on intermetallic formation. Higher rotational speeds resulted in thicker intermetallic layers and reduced the tensile strength. The study found that a sound weld surface was achieved at 1200 rpm, which allowed for proper diffusion, controlled intermetallic formation, and solid-solution phase development, resulting in the highest tensile strength. The microstructure of the joint revealed a composite-like structure with dispersed Cu, Ag, and Zn particles in the Al matrix. The nugget zone displayed several phases, including Al-Zn solid solution,, (Ag-Cu) rich, and , which contributed to the highest tensile strength (156.19±10.08 MPa). The optimal joint strength and efficiency were observed at 1200 rpm, emphasizing the importance of rotational speed. At 1200 rpm, the fracture surface exhibited dimples, indicating ductile fracture. The incorporation of the Ag and Zn interlayers helped reduce the formation of highly brittle intermetallic compounds (IMCs), promoting less harmful phases and contributing to ductile fracture behaviour and the highest tensile strength.