Graphene-Assisted Chemical Magnetorheological Polishing of TC4 Titanium Alloys
TC4 titanium alloy, a representative α+β dual-phase alloy, exhibits high specific strength, corrosion resistance, and biocompatibility but remains a classic difficult-to-machine material due to high chemical reactivity, low thermal conductivity, and complex phase-dependent mechanical behavior. Conventional polishing routes yield low material removal rates and poor surface consistency. This work formulates a graphene-assisted chemical magnetorheological polishing fluid comprising 0.40 wt.% monolayer graphene flakes, 15 wt.% carbonyl iron powder, 5 wt.% alumina abrasives, and 3.0 wt.% hydrogen peroxide as the primary oxidant. The catalytic role of graphene in the Fenton reaction is quantified via real-time oxidation-reduction potential (ORP) monitoring, immersion tests, and X-ray photoelectron spectroscopy (XPS). Graphene elevates the ORP from 337 mV to 347 mV at 30 min and increases the high-valence Ti4+ fraction in the surface oxide layer from 54.81 at.% to 60.13 at.%. Concurrently, graphene reduces the average polishing force by 50% (from 0.26 N to 0.13 N) and improves force stability, confirming a lubrication effect at the pad-workpiece interface. Single-factor experiments on machining gap and spindle speed identify an optimized condition of 1.0 mm gap and 400 rad/min, under which surface roughness Sa decreases from 350 nm to 75 nm within 15 min. The results establish that graphene delivers dual catalytic-oxidation and lubrication functions, enabling efficient, high-integrity finishing of TC4 titanium alloy and offering a viable route for ultra-precision surface treatment of complex hard-to-machine materials.