Fabrication and Characterization of Porous Micro-arc Oxidation/Al Composite Coating: Bio-inspired Strategy from Cancellous Bone Structure

摘要

Based on the trabecular bone structure, a porous micro-arc oxidation (MAO) coating and a MAO/Al composite coating were fabricated on AZ31D Mg alloy. Surface morphology, cross-section morphology, coating composition, and coating thickness were observed by scanning electron microscopy, energy dispersive spectrometry, and x-ray diffraction. Then, force-dampening and energy-absorbing effects of the coatings were explored by a constant kinetic energy impact experiment, to explore their dampening stress and reducing vibration values applying in engineering structure subjected to impact or vibration stress. Results show that large plastic deformation and cracks formed in the AZ31D Mg alloy after impact, and the MAO coating hindered the formation of the defects due to its higher stiffness. In addition, MAO enhanced the energy-absorbing ability of the Mg alloy, which is beneficial for vibration reduction. However, the MAO coating had a rough and brittle surface, and when Al was used to protect it, its force-dampening effect, energy-absorbing effect, and plastic deformation resistance had the evolution trend approaching the Mg alloy substrate but with improved crack resistance. MAO can be an optimization method for enhancing the plastic deformation resistance and vibration reduction effect of Mg alloy as structure material, and Al can be used to enhance its crack resistance.