Investigation of microstructure and electrochemical corrosion tendency of the Al/CeO2 interface in the 7075-CeO2 aluminum matrix composites: experiments and calculations

In this paper, the 7075-CeO2 1wt. % aluminum matrix composites (7075-CeO2 AMCs) were prepared by spark plasma sintering and ultrasound-assisted casting. The Al/CeO2 interfacial structure in the 7075-CeO2 AMCs was investigated, and the tendency of hydrogen evolution corrosion was discussed. According to the results of the hardness effect of solution treatment and artificial aging, CeO2 delayed the precipitation of the precipitated phase, and the main enhanced phase of the peak-aging sample was η'. The theoretical calculation showed the segregation energies of Mg and Zn atoms at the Al/CeO2 interface were -0.33eV and -0.38eV, respectively, indicating strong trapping of Mg and Zn atoms at the Al/CeO2 interface, and this calculation was in agreement with the experimentally observed phenomenon. The analysis of transmission electron microscopy images showed that the main product of the Al/CeO2 interfacial reaction was Ce3Al11, and Ce3Al and Al were distributed on Ce3Al11. This indicates the interfacial reaction of Al/CeO2 is Al-Ce alloying. The results of the electrochemical test and electrochemical impedance spectroscopy analysis showed that the Ce(OH)3 passivation film generated by the combination of Ce3+ and OH- was able to inhibit the localized corrosion activity on the sample surface. Calculations of surface work function, Fermi energy level, and the hydrogen adsorption free energy (∆GH*) show that the ∆GH* of MgZn2 was 0.05eV, the surface work function of Ce3Al11 and Ce3Al was 3.70 and 2.46eV, and the ∆GH* was -0.25 and -0.57eV, respectively. This demonstrates that the weak regions for the corrosion resistance of the Al/CeO2 interface were MgZn2, Ce3Al11, and Ce3Al. •CeO2 delayed the precipitation of the precipitated phase, and the main enhanced phase of the peak-aging sample was η'.•Theoretical calculations and experimental phenomena confirm that the Al/CeO2 interface acts as strong traps for Mg and Zn.•The interfacial reaction of the Al/CeO2 interface is Al-Ce alloying•The weak regions for the corrosion resistance of the Al/CeO2 interface were MgZn2, Ce3Al11, and Ce3Al.