Strategies to improve joint strength of friction lap welded AA7475/PPS hybrid joint with surface pre-treatment on AA7475

Abstract

Friction lap welding (FLW) technology has recently emerged as a promising joining technology to join aluminium alloys and polymers. The strength of the metal-polymer hybrid joint can be enhanced by surface pre-treating of the metal. In this study, FLW experiments were performed on the surface pre-treated aluminium alloy 7475-T761 (AA7475-T761) with Polyphenylene sulfide (PPS) polymer. Three different kinds of laser texturing patterns were made, includes grooves, circles, and square grid patterns. In addition, the alloy surface is also roughened with the wet grinding process. Surface roughness, surface topography characteristics, and contact angle (CA) were measured for treated surfaces. Furthermore, the tensile lap shear strength (TLS) of surface pre-treated FLWed joints was compared to that of untreated weldments. Results showed that the wet grinding process had minimal effect on joint strength. TLS was enhanced by 120% on a laser-textured square grid-patterned substrate in comparison with the untreated specimen weldment. The X-ray photoelectron spectroscopy (XPS) examination confirmed that the AlOC chemical bond represents the secondary bonding mechanism along the micro-mechanical interlocking.