The effect of La/Nd ratio on microstructure and mechanical properties of as-cast AZ91D alloys were investigated. The alloys were produced by casting the molten metal into a preheated steel mould. Microstructures were investigated by XRD and SEM (equipped with EDS). The hardness measurement was carried out by Brinell hardness (HB) digital display tester. Compression tests were conducted at both room and high temperatures (20°C and 150°C). Microstructural characterizations reveal that the area fraction of the β-Mg 17 Al 12 phase changed with the variation of La/Nd ratio. The area fraction of the β-Mg 17 Al 12 phase decrease significantly and then increased slightly with the increase of La/Nd ratio. Besides, the results show that the addition of La and Nd contributed to the formation of needle-like phase Al 11 RE 3 . Meanwhile, the Brinell hardness and high-temperature compression properties of this alloy reach the maximum values (67 HB and 330 MPa, respectively) when the La/Nd ratio is 2/3. In this alloy, the amount of Al 11 RE 3 phase is 51/TA and the average length is 69.55 μm. Moreover, a generation model of Al 11 RE 3 is established and the growth mechanism of Al 11 RE 3 is analyzed. This work thus has proved that La/Nd ratio has a great effect on the microstructure and mechanical properties of AZ91.
Anodic oxide films were prepared by anodic oxidation on the surface of ADC12 aluminum alloy and their corrosion properties were explored. The original samples, anodized samples, and sealed samples were placed in the salt spray corrosion chamber and were taken out at different times. Then the corrosion resistance of the ADC12 aluminum alloy was discussed, and the electrochemical corrosion test was researched. The results indicated that the surface of the original samples reveals many large-area pits after salt spray corrosion, while the sealed samples present a smoother surface. The dense oxide films on the surface of the base metals effectively prevent Cl[Formula: see text] entering into aluminum alloys especially after sealing. Electrochemical tests including the potential polarization curve and electrochemical impedance spectroscopy (EIS) as functions of exposure time were employed to reveal the corrosion behavior of surface layers. After the sealing treatment on the oxide films, the corrosion potential moved in the positive direction, the corrosion current density decreased, and the corrosion resistance of the ADC12 aluminum alloy was significantly improved.
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