Design and preparation of Fe–FeAl2O4/Al2O3 magnetic abrasive particles with a gradient core–shell structure

The precision and efficiency of magnetic abrasive finishing (MAF) are highly dependent on the performance of magnetic abrasive particles (MAPs), where strong interfacial bonding between the ferromagnetic matrix and hard abrasive phase is crucial. In this study, a novel type of core–shell structured MAPs (Fe–FeAl 2 O 4 /Al 2 O 3 ) was successfully synthesized via a two-step process involving ball milling and subsequent heat treatment. The approach enabled the uniform coating of Al 2 O 3 onto spherical Fe powder, followed by the in-situ formation of an FeAl 2 O 4 interlayer at the interface during sintering at 1250 °C. The influence of sintering time (0.5 h and 1 h) on phase composition, magnetic properties, and interfacial structure was systematically investigated. Results indicate that the sample sintered for 0.5 h exhibited optimal magnetic properties, including a high saturation magnetization of 173.96 emu/g and a low coercivity of 13.01 Oe, along with the best service performance. Prolonging sintering to 1 h led to decreased saturation magnetization (164.46 emu/g) and increased coercivity (14.41 Oe) due to oxidation of the Fe matrix and excessive growth of the brittle FeAl 2 O 4 phase. The designed MAPs demonstrated excellent finishing capability, reducing the surface roughness of a titanium alloy tube from an initial Ra of 0.428 μm–0.096 μm. This work provides a feasible strategy for fabricating high-performance MAPs with enhanced interfacial bonding and prolonged service life, showing significant potential for precision surface finishing applications.