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

Abstract

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.