Microstructure of the hypoeutectic Al-Mg alloy solidified at 4 GPa high pressure

High pressure solidification rules of Al-Mg alloy needs to be discussed further for its wide range of application. Microstructures and phases of Al-25wt%Mg alloy solidified at 4 GPa were studied by optical microscope, X-ray diffractmeter, energy dispersive X-ray spectroscopy and transmission electron microscopy (TEM). The microstructure evolution mechanism of Al-25Mg alloy under high pressure was analyzed. The result shows that the alloy consists of α-Al phase and Al₃Mg₂ phase under normal pressure. However, only Al₁₂Mg₁₇ phase forms without Al₃Mg₂ phase at 4 GPa. In addition, Mg concentration in α-Al phase increases and that of the lattice constant also increases. The α-Al dendrite presents the broken arms under normal pressure, after high pressure solidification, the morphology of the dendrite tends to integrate and the size of the dendrite arms decreases.