Sustainable and Optimized Chemical Magneto‐Rheological Finishing of Ti64 Alloy for Enhancing Surface Finish Through pH Regulation

This study developed a sustainable chemical pretreatment process with magnetorheological (CH‐MR) finishing. The CH‐MR process is a hybrid finishing technique that synergizes the integration of eco‐friendly, biodegradable chemicals, which selectively oxidize and soften the surface, facilitating MR finishing to achieve nanolevel roughness with reduced processing time and enhanced surface quality. Central composite design is employed to evaluate the effects of critical parameters, including pH value, working gap (WG), rotational speed (RS), and current (C), on the surface roughness of the Ti64 alloy (Sa). Analysis of variance reveals pH as the most influential parameter contribution (17.98%), followed by WG (14.89%), RS (10.33%), and C (9.21%), respectively, and the remaining variation is attributed to parameter interactions. Optimization yields a minimum Sa of 38.20 nm after 30 min of finishing under the optimal parameters of a pH of 5, a WG of 0.5 mm, an RS of 150 rpm, and a C of 3.5 A. The surface morphology and integrity are assessed using field‐emission scanning electron microscopy and atomic force microscopy, confirming a significant reduction in surface roughness and improvements in quality, with fewer surface defects. X‐ray photoelectron spectroscopy further clarifies the finishing mechanism by associating surface oxidation levels with improved chemical‐mechanical synergy.