a b s t r a c t a r t i c l e i n f o Available online xxxxAnodic coatings with and without superfine Al 2 O 3 particles were prepared on AZ31 magnesium alloy by anodizing in an environmentally friendly alkaline solution. The microstructure and morphology of the coatings were analyzed using X-ray diffraction and scanning electron microscopy equipped with energy dispersive spectroscopy. The corrosion resistance of the uncoated AZ31 substrate and the anodic coatings was evaluated in 3.5% NaCl solution through potentiodynamic polarization tests. Friction and wear tests were performed to evaluate the wear resistance of the samples. The results show that the composite oxide coating has better corrosion resistance than the coating without Al 2 O 3 nanoparticles. The microhardness of the composite coating with reinforced Al 2 O 3 nanoparticles is up to 358 HV. When rubbed at 10 N load for 3 min during sliding against GCr15 at ambient temperature, the wear loss of the film was about 0.04 mm 3 , which is about one-tenth of that of the anodizing coating without nanoparticles. Therefore, the composite anodizing coating with Al 2 O 3 nanoparticles shows better anti-corrosion and anti-wear properties than the coating without Al 2 O 3 nanoparticles.

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In this paper, electron backscatter diffraction and various other characterization and analysis techniques including X-ray diffraction, electron channeling contrast imaging and energy-dispersive spectrometry were jointly employed to investigate microstructural and textural changes of a hot-rolled Ti-6Al-4V (TC4) sheet after annealing at 800°C for 5 h. In addition, the hardness variation induced by the annealing treatment is rationalized based on revealed microstructural and textural characteristics. Results show that the TC4 sheet presents a typical dual-phase (a ? b) microstructure, with a-Ti as the major phase and short-rod-shaped b-Ti (minority) uniformly distributed throughout the a matrix. Most of a grains correspond to the un-recrystallized structures with a typical rolling texture (c//TD and \11-20[//ND) and dense low angle boundaries (LABs). After the annealing, the stored energy in the as-received specimen is significantly reduced, along with greatly decreased LABs density. Also, the annealing allows recrystallization and grain growth to occur, leading to weakening of the initial texture. Furthermore, the water quenching immediately after the annealing triggers martensitic transformation, which makes the high-temperature b phases be transformed into submicron a plates. The hardness of the annealed specimen is 320.5 HV, lower than that (367.0 HV) of the as-received specimen, which could be attributed to reduced LABs, grain growth and weakened texture. Nevertheless, the hardening effect from the fine martensitic plates could help to suppress a drastic hardness drop.