As mentioned above, the mechanical properties of Mg nd Zn magnesium alloy can be further improved by rheo squeeze casting. However, the mechanical properties of the alloys decrease sharply when the temperature reaches above 250 ℃. According to the existing research, the mechanical properties of Mg alloy can be effectively improved by adding appropriate amount of Y element.
For example, su et al. Found that in mg – 2.4nd – 0.2zn – 0.4zr – XY (0, 2.5, 4.0, 6.0 wt%) alloy, with the increase of Y content, the effect of grain refinement is enhanced, and after heat treatment, the number of β′ phase in the alloy increases, and the mechanical properties are improved. Hu et al. Found that adding 0.5wt.% y to mg-6zn-1mn-4sn alloy can form mgsny high temperature stable phase, enhance the aging strengthening effect of the alloy, and obtain high density rod like β′ phase, thus obtaining excellent mechanical properties. Zhao et al. Have shown that the addition of 1wt.% y to mg-8li-3al-2zn alloy can refine the grain size, form al2y phase and improve the mechanical properties of the alloy. Li et al. Found that adding 0.2wt.% y to mg-2.8nd-0.6zn-0.4zr alloy can improve the yield strength at room and high temperature. The increase of high temperature tensile strength is mainly due to the formation of β″, β′, β 1 and γ phases in the alloy.
When the Y Content in the alloy is higher, the elongation of the alloy decreases, the density increases and the cost is higher. The addition of trace y element can effectively improve the mechanical properties of the alloy while maintaining low density and cost. In this chapter, the effects of Y addition on the microstructure and mechanical properties of Mg nd Zn alloy at room and high temperature were studied. The microstructure and mechanical properties of the alloy were studied by rheo squeeze casting. The actual composition of the metal mold cast Mg – 0.43nd – XY – 0.08zn – 0.11zr (x = 0, 0.03, 0.06 and 0.12 at.%) alloy is atomic percentage for discussion.