Abrasive flow machining (AFM) process and ultrasonically assisted AFM technique (UAAFM) were carried out to polish micro-channel internal faces produced by selective laser melting (SLM). Both numerical simulation and experimental studies were investigated. Simulation results confirmed that the distribution of the flow velocity, absolute pressure, and turbulence intensity inside the S-shaped micro-channel exhibit significantly different. After loading ultrasonic-vibration, cavitation can indeed enhance the turbulence intensity. As the ultrasonic frequency increases, the cavitation area and turbulent kinetic energy increase accordingly. A set of AFM and UAAFM experiments were conducted. Compared with traditional AFM process, UAAFM owns better surface roughness and more uniform material removal at the same experimental condition.

High-entropy alloys (HEAs) were used to improve the hardness, wear resistance, and corrosion resistance of steel surfaces by laser cladding due to their outstanding mechanical and corrosion resistance properties. However, there are only a few literary works on the improvement of wear resistance on the aluminum alloy surface by HEAs. In this work, the wear performance of laser cladded Al_0.8CrFeNiCoAlCu_x HEA coating on aluminum alloy with different Cu contents was investigated in detail. Moreover, phase structure, microstructure, bonding shear strength, and corrosion resistance of HEA coatings were studied by XRD, SEM, tensile device, and electrochemical workstation. The result shows that with the increase of the Cu content, the structure of the coatings changed from BCC1 and BCC2 phases to BCC1, BCC2, and FCC1 phases. Evident cracks were observed in the Al_0.8CrFeCoNi HEA coating. Meanwhile, when x = 0.25, the cracks disappeared, but the bonding shear strength was 79.6 MPa, only 34.7% of the substrate. At 0.5 ≤ x ≤ 1, the bonding shear strength of the Al_0.8CrFeCoNiCu_x HEA coatings went above 175.2 MPa. As Cu promotes the formation of FCC phase, the hardness of the Al_0.8CrFeCoNiCu_x HEA coating decreased as the Cu content increased. The effect of Cu on wear resistance has the same trend as with hardness. The wear rate of Al_0.8CrFeCoNiCu_0.5, Al_0.8CrFeCoNiCu_0.75, and Al_0.8CrFeCoNiCu HEA alloys is only 3.4%, 4.02%, and 5.42%, respectively, of the substrate. The wear mechanisms of the substrate are that of delamination fracture and serious adhesion wear, while the wear mechanisms of Al_0.8CrFeCoNiCu_x (0.5 ≤ x ≤ 1) HEA coatings are that of adhesive and abrasive wear. The corrosion resistance of Al_0.8CrFeCoNiCu_x (0.5 ≤ x ≤ 1) HEA is better than that of the substrate in 1 mol l⁻¹ H₂SO₄ solution. Al_0.8CrFeCoNiCu_0.5 has the best corrosion resistance that is characterized by pitting and intergranular corrosion.

Preparing a coating with excellent mechanical properties on aluminum substrates by laser cladding has always been challenging because of the low melting point and high chemical activity of Al. In this study, we designed Al_0.8FeCoNiCrCu_0.5Si_x (x = 0, 0.2, 0.3, 0.4, and 0.5) high-entropy alloys (HEAs) as cladding materials. The proposed study aims to exploit the unique high-entropy effect of HEAs to restrict the the formation of hard and brittle intermetallic compounds via the reaction between Al in the substrate and added powders, thereby enhancing the quality of the formed coatings and ultimately improving the surface properties of the Al alloy. Results show that with an increase in the Si content, the structure of the Al_0.8CrFeCoNiCu_0.5Si_x coating changes from FCC + BCC1 + BCC2 to BCC1 + BCC2. The hardness of the Al_0.8FeCoNiCrCu_0.5Si_x coating first increases and then decreases with an increase in the Si content. The coatings with the highest and lowest hardness were those with compositions of Al_0.8FeCoNiCrCu_0.5Si_0.4 (592HV_0.2) and Al_0.8FeCoNiCrCu_0.5 (412HV_0.2), respectively, which is approximately seven and five times greater than that of the substrate, respectively. The effect of Si content on the wear resistance of the coating is the same as its effect on the hardness. The wear rates of coatings with different Si contents range from 1.19 × 10⁻⁶ mm³ Nm⁻¹ to 8.99 × 10⁻⁷ mm³ Nm⁻¹ and are only 0.34% to 0.25% of the substrate. Obvious, the Al_0.8FeCoNiCrCu_0.5Si_x HEAs can be used as coating materials to improve the mechanical properties of an Al alloy surface.