Research on the effect of microtexturing pretreatment on laser welding of CFRTP and aluminum alloy

Abstract

With the lightening tendency in the automobile and aircraft industry, the aluminium (Al) alloy and the carbon fiber reinforced thermal polymer (CFRTP) has been widely used. The CFRTP component always needs to be joined with Al alloy to form a CFRTP/Al alloy composite structure. Due to the large differences in the physicochemical properties of CFRTP and Al alloy materials, it is difficult to join with each other. Laser stir welding technology was applied to join CFRTP and Al alloy dissimilar materials in this research. In order to improve the CFRTP/Al alloy joining strength, a surface pre-treating method (laser micro-engraving) was proposed in this paper. Three micro-scale structures were designed and prepared on 7075 Al alloy by surface laser micro-treatment, which are linear grooves, mesh grooves and circular grooves. The morphology and dimensions (width and depth) of the microstructure on the strength of CFRTP / Al alloy joints were studied. The interface morphology and the fracture morphology of the joint were observed by the laser confocal microscopy and the scanning electron microscopy (SEM). Furthermore, the joining mechanism and failure mechanism of the CFRTP/Al alloy joint were explored. The results indicated that the microscale structures play an important role in improving the mechanical properties of Al alloy and CFRTP joins under different laser micro-engraving.