Comprehensive regulation of carbon nanotubes on laser welded joints of aluminum alloy: From morphology, solidification, microtexture to properties

Abstract

Laser welding of aluminum alloys is prone to porosity formation, which significantly compromises joint strength. In this study, the successful incorporation of carbon nanotubes(CNTs) into aluminum alloy welds not only increased welding speed but also enhanced joint strength while maintaining comparable weld penetration depth. The key point is that the comprehensive impact of CNTs on the joint has been systematically studied. Differential scanning calorimetry(DSC) and phase diagram analysis revealed that the exothermic reaction between CNTs and the aluminum matrix promoted the formation of Al₄C₃. Mechanical properties analysis demonstrated that the maximum tensile strength of the CNTs reinforced joint reached 326 MPa, outperforming most laser welding processes. On a microstructural level, CNTs refined the grain size of the weld fusion zone by 35.5 %, facilitating dynamic recrystallization and resulting in anisotropic grain structures. Microtexture analysis showed that some CNTs were dispersed within the weld, providing a stress transfer pathway at the CNTs/aluminum interface. This work comprehensively reveals the enhancement effect of carbon nanotubes on joints, and provides new potential solutions for optimizing the welding process of power battery casings.