Study on non-equilibrium solidification microstructure of Al–Cu3–Si–Mg alloy by MMDF

Abstract Al–Cu3–Si–Mg wheel hubs were prepared by molten metals die forging (MMDF). The as-cast microstructure morphology of the alloy formed under pressure was observed by optical microscope and scanning electron microscope. The granular phases θ (Al 2 Cu) were distributed in the α –Al grains, and the cross phases β (Mg 2 Si) grew near the grain boundary in the α –Al grains. Polygonal compounds φ (Al x Ti 9 La 2 Ce 6 Cu) and irregular eutectic structures mainly formed by ( α + Al 2 Cu) eutectic formed under non-equilibrium solidification were found at the grain boundaries. Q (Al 5 Cu 2 Mg 8 Si 6 ) phases were found at the intersection of grain boundaries. With the increase of pressure, the proportion of irregular eutectic structures ( α + Al 2 Cu) decreased from 7.3% to 5.2%. Combined with microstructure analysis and thermodynamic software analysis, the non-equilibrium solidification path was determined as follows: L → L + φ → L + α + φ → L + ( α + e ) + α + φ → ( α + e ) + Q + α + φ → ( α + e ) + Q + [ α + θ ] + φ → ( α + e ) + Q + [ α + θ + β ] + φ