Effect of Cu on microarc oxidation coated Al– x Cu alloys

Abstract

Microarc oxidation (MAO) coatings were produced on the Al–Cu alloys at different oxidation times. Surface morphologies, phase composition and residual stress, and wear resistance were analysed by SEM and a laser scanning confocal microscopy, X-ray diffraction, and reciprocating friction and wear tester, respectively. Increases in surface roughness, porosity, cracks, thickness, and α-Al₂O₃ content were found in the MAO coatings on Al–4.5Cu alloy. Presence of intermetallic Al₂Cu in the Al–4.5Cu alloy improved wear resistance and induced residual compressive stress formation in the coatings. Heat accumulation of intermetallic Al₂Cu was the key factor that led to the differences in coating microstructure and nature of residual stress. In addition, mechanical properties of the coated samples were slightly changed compared to that of bare Al–Cu alloys. Presence of intermetallic Al₂Cu was advantageous to wear resistance and oxide film formation of MAO coated Al–Cu alloys.