Investigation of the mechanical behavior and microstructure of aluminum-copper bimetallic tubes connected by the rotary swaging method

Abstract Rods, tubes, and similar components undergo the rotary swaging process to reduce cross-sectional area and enhance mechanical properties. This process offers significant advantages, including increased tensile strength, material strength improvement, reduced surface roughness, and reduced scraps. However, its use in producing double-wall tubes has been less common. This work investigated the rotary swaging process for producing aluminum-copper bimetallic double-wall tubes with an aluminum coating. The research specifically examines the impact of the presence or absence of a mandrel during the rotary swaging process on the mechanical properties of these double-wall tubes. The results indicate that using a mandrel not only enhances adhesion and sample strength but also leads to increased hardness in both axial and radial directions. Additionally, microscopic analyses, including optical microscopes (OM) and scanning electron microscopes (SEM) equipped with energy dispersive spectroscopy (EDS), and mechanical tests such as compression, peeling, hardness measurements, and bending tests confirm that mandrel-assisted samples exhibit more desirable mechanical properties. Without the use of a mandrel, the layers are not effectively bonded together, resulting in gaps in certain areas, the average of which is about 11.95 μm. Additionally, the yield stress for double-layer tubes without a mandrel is equal to 153 MPa, whereas the yield stress for double-layer tubes with a mandrel is equal to 170 MPa, indicating that the samples produced with a mandrel are stronger than those without.