Abstract
<title>Abstract</title> <p>To address the poor surface quality of additively manufactured complex internal channels with high aspect ratios, as well as the difficulty of achieving both high finishing efficiency and good machining uniformity using conventional finishing methods, this study investigated ultrasonic-assisted water-based abrasive flow finishing of a 90° bent AlSi10Mg aluminum alloy channel fabricated by selective laser melting. Fluid simulations were performed to analyze the pressure field and cavitation characteristics inside the channel. The effects of inlet pressure and ultrasonic parameters on the flow-field characteristics were examined. Surface roughness measurements and morphology observations were then used to evaluate the finishing performance under different processing modes. The results show that, at an inlet pressure of 1 MPa, the dynamic pressure distribution inside the channel was relatively uniform, which helped avoid local over-finishing. Under an ultrasonic amplitude of 25 µm and a frequency of 20 kHz, the gas volume fraction in the channel increased markedly, providing favorable conditions for cavitation. Compared with unidirectional processing, bidirectional processing effectively improved the machining non-uniformity between the inlet and outlet sections, although its improvement in the corner region was limited. After ultrasonic assistance was introduced, the synergistic action between cavitation-induced micro-jets and abrasive particles significantly enhanced the material removal capacity in the corner region, thereby improving the surface quality of the difficult-to-finish area. After 30 min of ultrasonic-assisted bidirectional processing, the surface roughness at the channel corner decreased from the initial Ra 13.725 µm to Ra 1.730 µm, while the surface roughness at both the inlet and outlet sections decreased to Ra 0.529 µm. In addition, ultrasonic-assisted bidirectional processing for 20 min achieved a surface finishing effect comparable to that obtained by bidirectional processing without ultrasound for 30 min, indicating a 50% improvement in processing efficiency. Overall, ultrasonic-assisted water-based abrasive flow finishing can effectively improve the surface quality, machining uniformity, and processing efficiency of additively manufactured high-aspect-ratio internal channels. This study provides a technical reference for the efficient precision finishing of complex internal channel components.</p>