Effect of Gd content on microstructure and mechanical properties of Mg-Y-RE-Zr alloys

Four kinds of Mg-Y-RE-Zr alloys with different Gd contents were prepared, and the effect of Gd content on microstructure and mechanical properties of the alloys was researched. Based on the experimental investigation, the compounds at the grain boundaries are mainly Mg24Y5, Mg41Nd5, and Mg5Gd phases. The average grain size of as-cast alloys is 50–60 μm. After T4 (535 °C, 24 h) treatment, Mg5Gd phases mostly decompose and dissolve into the matrix, and the disperse spotted phases are mainly Mg24Y5 and Mg41Nd5 phases. After extruding and ageing (250 °C, 5 h), the grain size is refined and some grains abnormally grow up to about 40 μm. With Gd content increasing, the ultimate tensile strength, yield strength of as-cast alloys and the extruded bars after ageing are improved, but the elongation is decreased.