Abstract
The effects of modification of Mg-2Gd alloy with Ag and Ca elements on its microstructure and mechanical properties were investigated. Mg-2Gd alloy and two ternary alloy systems Mg-2Gd-xAg (x=1, 2 wt%), Mg-2Gd-xCa (x=0.4, 0.8 wt%) were prepared by permanent mould casting. The additions of Ag or Ca contribute to a visible change in the microstructure and mechanical properties. For Mg-2Gd-xAg alloys, a new ternary intermetallic phase (IMP) Mg52Gd3Ag5 is formed. Besides the ternary phase, Mg-Gd binary IMP Mg5Gd is also present in both Mg-2Gd-xAg alloys. With increasing the content of Ag, their grain size decreases and the amount of eutectic phase rises, which lead to improvement of the tensile and compressive properties. For Mg-2Gd-xCa alloys, the Ca addition leads to the formation of Mg2Ca while Mg5Gd is still present. Small amount of Ca addition also leads to improvement of tensile and compressive properties. In contrast, more addition of Ca reduces the tensile strength, because the grain size increases and becomes non-uniform, although the volume fraction of Mg2Ca increases. Both Ag and Ca contribute to slight improvement of the hardness.
