Significant reinforcement of mechanical properties in laser welding aluminum alloy with carbon nanotubes added

Abstract

Laser welding 2A12 (Chinese grade) aluminum alloy with carbon nanotubes (CNTs) added was carried out, and the mechanism of CNTs strengthening joints was explored in detail. Firstly, to achieve the same penetration depth, single laser welding and laser welding with CNTs require speeds of 40 mm/s and 60 mm/s respectively. The addition of CNTs increases the welding efficiency by 50%. Furthermore, the maximum tensile strength of the joint with CNTs increased by 45.5% to 326 MPa. Fracture analysis showed that the significant improvement in the mechanical properties of the joint was partly due to the CNTs reducing the pore size by an order of magnitude. Then, phase analysis reveals that a large number of precipitated phases increase the dislocation density and provide a basis for dislocation strengthening. The failure mode of CNTs is pulled out and the HRTEM test found that the CNTs are dispersed in the aluminum matrix. Indicating that the CNTs in the weld are tightly bonded to the surrounding Al matrix and load transfer from the matrix to CNTs is improved. This work provided an idea of laser welding aluminum with high efficiency and significantly enhanced mechanical properties. Finally, the process window for laser welding 2A12 aluminum alloy has also been established.