Microstructure and corrosion behavior of as-cast ADC12 alloy with rare earth Yb addition and hot extrusion

The effects of rare earth ytterbium (Yb) addition and hot extrusion on the microstructure and corrosion behavior of as-cast ADC12 were studied by optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD). The experimental results demonstrate that both the Si phase and β-Al5FeSi phase in the alloy with 0.9 wt% Yb have been remarkably refined, and the Al3Yb intermetallic compound has also been obtained. The Si, β-Al5FeSi, and rare earth phases are further refined in the alloy at 0.9 wt% Yb and hot extrusion. The results of the immersion corrosion tests and electrochemical experiments show that the corrosion current density (8.56 µA/cm2) of the alloy with 0.9 wt% Yb addition and hot extrusion is 50.6% lower than the untreated alloy (17.33 µA/cm2), and the polarization resistance (9252 Ω·cm2) was 71.3% higher than the untreated alloy (2654 Ω·cm2). The corrosion in the cathode phase in the micro-battery was refined to varying degrees attributable to the addition of Yb and hot extrusion, where the cathode reaction in the corrosion process caused a decrease of the corrosion rate.