Fabrication of Al-Si coating on Ti-6Al-4V substrate by mechanical alloying

Al-Si coatings were synthesized on Ti-6Al-4V alloy substrate by mechanical alloying with Al-Si powder mixture. The as-prepared coatings had composite structures. The effects of Al-Si ratio, milling duration and rotational speed on the microstructure and oxidation behavior of coating were investigated. The results showed that the continuity and the anti-oxidation properties of the coating were enhanced with the increase of Al-Si weight ratio. The thickness of the coating largely increased in the initial 5-hour milling process and decreased with further milling. A rather long-time ball milling could result in the generation of microdefects in coating, which had an adverse effect on the oxidation resistance of coating. Both the thickness and the roughness of the coating increased with the raise of rotational speed. The low rotational speed would lead to the formation of discontinuous coating. The rotational speed had a limited effect on the coating oxidation behavior. Dense, continuous and high-temperature protective Al-Si coatings could be obtained by mechanical alloying with Al-33.3 wt.% Si powder at the rotational speed ranging from 250 to 350 rpm for 5 h.