Effect of anodizing pretreatment on laser joining CFRP to aluminum alloy A6061

Phosphate anodizing pretreatment of aluminum alloy A6061 was carried out before carbon fiber reinforced plastic (CFRP) was joined to A6061 using fiber laser. The results show that this kind of pretreatment could remarkably strengthen the joining between CFRP and A6061. With anodizing time varying between 10 min and 30 min, shear strength of over 35 MPa were achieved for the CFRP/A6061 dissimilar joints. The highest shear strength could reach 41.8 MPa under optimized joining parameters, which was approximately 8 times as high as that of the joint without anodizing pretreatment. From the observation with SEM, the nanoscale porous oxide layer that was produced on the surface of A6061 after anodizing pretreatment improved the wettability of CFRP on A6061, which leaded to a stronger mechanical anchoring effect at the interface. With the investigation of the transition layer at the interface by XPS, new chemical bonding of 'Al-O-PA6' was detected in the dissimilar joint of CFRP and anodized A6061. Therefore, it made clear that the oxide layer could strengthen the mechanical anchoring effect as well as promote the potential of chemical reaction between CFRP and aluminum. (C) 2016 Elsevier Ltd. All rights reserved.