Comparative study of micro-sized Al particles enhancing the thermal joining of aluminum alloy-PA66 without or with reinforcement

The huge thermal difference between the aluminum alloy and polymer led to a low interface bonding strength, hindering the application of hybrid joints in the industries. Micro-sized aluminum (Al) particles were introduced into the polyamide 66 (PA66) resin substrates to improve the laser thermal joining of aluminum alloy to PA66 considering the heat conduction of metal particles. Results indicated the resin was physically reinforced after adding Al particles, enhancing the melting point and decomposition temperature due to the constraint on the polymer chain movement. The surface energy of PA66 resin was also increased because of the increase of polar functional groups, resulting in an enhancement of adhesion force between the aluminum alloy and resin. Furthermore, 3D thermally-conductive network formed between particles and resin substrates owing to the thermal vibration caused by Al electrons during the heat conduction, thereby strengthening the thermal conductivity of resin. This improved the thermal microscopic conductance at the interface, and the joining area at the interface dependent on the molten resin was thus enlarged. Finally, the tensile-shear force and strength of joints after adding Al particles were both significantly improved, reaching 1.35 times and 1.44 times of those without Al particles under the optimal heat input, respectively. This was achieved by a synergetic strengthening effect of enhanced adhesion force and joining area, providing a new method to obtain the high-quality joints.