从上述结果可知，随着Zn元素添加量的增加，合金共晶相数量减少，而LPS

From the above results, as the additive amount of Zn elements to reduce the number of eutectic phase, while increasing the number of LPSO phase, in order to further understand the evolution of the alloy phase, to carry out different phase diagram of Zn content of the alloy is calculated. Gd is fixed to 8.5wt.%, Y content of 4.5wt.%, Obtained on phase diagram Mg-8.0Gd-4.5Y- Zn alloy, it is possible to analyze changes in the microstructure during solidification, to give different conditions at different temperatures under equilibrium solidification structure, as shown in FIG. In Mg-8.0Gd-4.5Y-0.7Zn alloy Example (1-5), when the temperature of molten alloy above the liquidus temperature (622 deg.] C), the alloy is a single liquid phase; at temperatures below 622 when ℃, gradually precipitated from the liquid alloy of α-Mg solid solution; when the temperature dropped to about 604 ℃, the end of solidification, the alloy phase all α-Mg solid solution; and when the temperature dropped to 430. ℃, starting from α-Mg in RMg5 precipitated phase, the content thereof is increased with decreasing temperature, the time until about 150 deg.] C, with substantially no amount RMg5 change with temperature change; when the temperature dropped to 200 ℃, started from the α-Mg precipitation R5Mg24 phase. The alloy is obtained at room temperature (25 ℃) equilibrium organization: α-Mg + R5Mg24 + RMg5 + LPSO.

From the above results, it can be seen that with the increase of Zn element addition, the number of alloy cocrystalline phases decreased, and the number of LPSO phases increased, in order to further understand the phase evolution of alloys, different Zn content alloy phase graph calculation was carried out. Fixed Gd is 8.5wt., Y content is 4.5wt., and a phase map of Mg-8.0Gd-4.5Y-Zn alloy is obtained, which can analyze the microtissue changes in the alloy solidification process and obtain the equilibrium solidification tissue under different temperature conditions, as shown in Figure 3. In the case of Mg-8.0Gd-4.5Y-0.7Zn alloy (Figure 1-5), the alloy is a single liquid phase when the temperature of the alloy liquid is higher than the liquid-phase line temperature (622 degrees C); When the temperature drops to about 430 degrees C, the RMg5 phase is extracted from the alpha-Mg, and the content increases with the temperature decreases, until the amount of RMg5 phase basically does not change with the temperature, and when the temperature drops to about 200 degrees C, the R5Mg24 phase is extracted from the alpha-Mg. The balance tissue of the room temperature (25 degrees C) of the alloy is: alpha-Mg-R5Mg24-RMg5-LPSO.

It can be seen from the above results that with the increase of Zn addition, the number of eutectic phases decreases, while the number of lpso phases increases. In order to further understand the phase evolution law of the alloy, the phase diagram calculation of the alloy with different Zn content is carried out. The phase diagram of mg-8.0gd-4.5y-zn alloy can be obtained by fixing the GD of 8.5wt.% and the Y Content of 4.5wt%, so as to analyze the microstructure change during the alloy solidification process and obtain the equilibrium solidification structure under different temperatures and conditions, as shown in Figure 3. Taking mg-8.0gd-4.5y-0.7zn alloy as an example (as shown in Fig. 1-5), when the alloy liquid temperature is higher than the liquidus temperature (622 ℃), the alloy is a single liquid phase; when the temperature is lower than 622 ℃, α - Mg solid solution is gradually precipitated from the alloy liquid; when the temperature drops to about 604 ℃, the solidification is over, and the alloy phase is all α - Mg solid solution; when the temperature drops to about 430 ℃, RMG is precipitated from α - mg The amount of rmg5 phase increased with the decrease of temperature until about 150 ℃, and r5mg24 phase began to precipitate from α - mg when the temperature dropped to about 200 ℃. The equilibrium structure of the alloy at room temperature (25 ℃) is α - Mg + r5mg24 + rmg5 + lpso.<br>