Ultrasonic cavitation strengthening and generation of superhydrophobicity for the surface of in situ (ZrB2 + Al2O3)/AA6016 matrix composite

To enhance the operating stability and durability of the aluminum matrix composite, the superhydrophobic surface is constructed on the substrate of in situ ZrB2 and Al2O3 nano-particle reinforced AA6016 matrix composite. The method incorporating ultrasonic cavitation treatment and low surface energy modification is applied. The performance of the obtained superhydrophobic surface is investigated through comprehensively analyzing micro and nano surface structures, roughness, water contact angle, chemical composition, and mechanical property. The results indicate that the water contact angle and water sliding angle of the specimen treated with cavitation for 9 min and then modified with fluorosilane attain 163.8° and 7.3°, respectively. High superhydrophobicity is accomplished. Long exposure to ultrasonic cavitation treatment results in the shift from hydrophobicity to hydrophilicity. The presence of particle-reinforced phases induces a pinning effect, causing the accumulation and entanglement of dislocations beneath the surface. This phenomenon leads to a 64.7 % increase in surface hardness, and the thickness of the work hardening layer reaches about 300 μm. The obtained conclusions shed light on the preparation of superhydrophobic surface for the aluminum matrix composite, and the application of aluminum matrix composites in harsh environment is expected to be broadened.