Effect of solution treatment and extrusion on evolution of microstructure in a Mg-12Dy-3Nd-0.4Zr alloy

Morphology and microstructure of precipitate phases in a Mg-12Dy-3Nd-0.4Zr (wt.%) alloy, before and after extrusion, has been studied using transmission electron microscopy (TEM) and X-ray diffraction (XRD). The eutectic phase, with composition of Mg5(Nd0.47Dy0.53), has a fcc crystal structure (a = 2.24 nm). The rectangular particles, at or near grain-boundaries in the solution treated state, has a fcc crystal structure (a = 0.526 nm) with composition of Dy17Mg3. Many elliptical particles, distributed almost homogeneously across the matrix in the as-extruded alloy, was identified a fcc crystal structure (a = 2.24 nm) with composition of Mg5(Nd0.50Dy0.50), which should be identical to the eutectic phases except the difference in morphology.