Abstract
The effect of aluminum addition on fundamental characters of as-cast Mg-4Y-xAl (x = 1, 2, 3 and 4 wt%) alloys were investigated by means of theoretical calculations, scanning electron microscopy, X-ray diffraction and Rietveld refinements. The lattice parameter and lattice volume of the α-Mg matrix decrease with increasing the content of Al, which is related to the content of Y and Al in solid solution. In the alloy system microstructures, Al11Y3, Al2Y and Mg24Y5 are principally formed, the content of Mg24Y5 decrease gradually with the increased of the Al content and finally disappeared when the Al content exceeded 3 wt%. This can be ascribed to the activation of standard molar enthalpies during the formation of those intermetallic compounds. Meanwhile, grain refinement was obtained after Al is added, owing to the Al2Y produced at the grain centers acts as active nucleant particle and the acicular shape Al11Y3 phases restrict the growth of α-Mg. In addition, the local solute (Y and Al) segregation inhibit the leading phase from growing in equilibrium also attributes to grain refinement. Addition of 4 wt% Al gives the alloy favorable mechanical properties at room temperature, the yield strength, ultimate tensile strength and elongation are 91 MPa, 186 MPa and 11.6%, respectively, mainly due to secondary phase strengthening and solid solution strengthening.
Published Version
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