Abstract: TiB₂ particles have a good strengthening effect on aluminum alloys. TiB₂/6061 composites were prepared by ultrasound-assisted remelting and dilution method, and the effects of TiB₂ particles on the microstructure and mechanical properties of 6061 aluminum alloy in as-cast and extruded+T6 heat-treated states were investigated.The results show that after adding 2wt% TiB₂ particles, the average grain size of the as-cast aluminum alloy is refined from 355.7 μm without adding TiB₂ to 117.5 μm. TiB₂ particles can promote nucleation and inhibit grain growth in recrystallization process. The yield strength of the extruded+T6 heat-treated TiB₂/6061 composites is 330 MPa, and the ultimate tensile strength is 385 MPa, which increases by 11.8% and 7% compared with that of the alloy without TiB₂ addition, respectively. The main types of reinforcement are thermal mismatch reinforcement and Orowan reinforcement.