Effect of Cu on microarc oxidation coated Al–xCu 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-Al 2 O 3 content were found in the MAO coatings on Al-4.5Cu alloy. Presence of intermetallic Al 2 Cu in the Al-4.5Cu alloy improved wear resistance and induced residual compressive stress formation in the coatings. Heat accumulation of intermetallic Al 2 Cu 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 Al 2 Cu was advantageous to wear resistance and oxide film formation of MAO coated Al-Cu alloys.

Effect of thermal conductivity on micro-arc oxidation coatings

“…Plenty of micropores with a diameter of <1.5 μm were found, and their distribution was homogeneous. In Figure 2(c), the distribution of micropores is consistent with the small morphology of the dispersed Al 2 Cu phase shown in previous work [24]. Because the EC property of the alloy with 4.5 wt-% Cu is excellent and the TC property of Al 2 Cu phase is poor, the α-Al was easily dissolved near Al 2 Cu phase.…”

“…Because the second phase in the alloys with 1 and 4.5 wt-% Cu was analyzed in the previous study [24], only the surface morphology of the alloy with 3 wt-% Cu is shown in Figure 1. XRD patterns of previous study showed that a large amount of Al 2 Cu phase precipitated in the alloy with 4.5 wt-% Cu [24], which was due to the Cu content exceeding its solubility in Al matrix [38]. The Cu contents of 1 and 3 wt-% did not exceed the solution of Cu, and a large amount of Cu is soluble in Al substrate.…”

“…The Al alloys with 1, 3, and 4.5 wt-% Cu were fabricated. Preparation of the substrates and coatings, elements and mechanical properties of the Al alloys measurement, MAO equipment, electrolyte composition, electrical parameters, and the characterization of coatings were described in our previous study [24]. However, three samples were treated by MAO at one time, which was half the number of our previous study.…”

“…Due to the inhibition of RCS on crack initiation, controlling the process parameters of MAO to produce RCS in the coating was indispensable. Previous studies showed that Cu content and Al 2 Cu phase affected the nature of the RS in ceramic layers [23,24]. However, numerous Al 2 Cu phase was formed in the alloy with 4.5 wt-% Cu.…”

Antimicrobial properties dependence on the composition and architecture of copper-alumina coatings prepared by plasma electrolytic oxidation (PEO)

“…Copper is one of the most used biocides exhibiting excellent antibacterial and antifouling properties [3,15] in a wide range of surface materials, and it can also be employed in PEO coatings. The common strategies to incorporate copper species into the oxide layer of the PEO coating are using Al-Cu alloys as the metal precursor substrate [16][17][18][19][20] or adding copper species into the electrolyte during the anodization [3,15,21]. On the other hand, when the purpose is to fabricate a heterojunctioned material, a copper plating procedure can be performed after the anodization [22], forming a metallic layer over the oxide coating.…”