Uncovering the effects of Ce and superheat temperature on Fe-rich intermetallic and microporosity formation in aluminum alloy

The continuous accumulation of Fe impurities in recycled aluminum is a major obstacle for its wide application in fatigue sensitive parts due to the formation of Fe intermetallics and micropores. In this paper, we study the effects of rare earth elements and superheat temperature on the crystal structure of Fe-rich intermetallic and morphology of microporosity using micron-resolution phase-contrast lens magnification based X-ray computed tomography (XCT). Using image registration and U-net convolutional neural networks (CNN) algorithm, we first segmented the morphology of Fe-rich intermetallic and quantified their distribution as a function of Ce additions and superheating temperature. It was found that the addition of Ce elements promoted the microstructure refinement and restricted the growth of β-Fe intermetallics effectively. Lowering the superheat temperature from 780 °C to 680 °C does not show a linear relationship between porosity level and the reduction of the intermetallic volume fraction. In fact, we have found the size of eutectic Si and Fe-rich intermetallic is the smallest at 730 °C and the tensile strength at as-cast condition with a superheating at 730 °C and Ce addition can give the greatest elongation at 4.26%, and yield and tensile strengths at 175.3and 249.5 MPa, respectively.