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本文通过光学显微镜、X射线衍射仪、扫描电镜等分析研究了合金化元素Zn对GW系镁合金砂型铸造组织和性能的影响。研究结果表明：GW系镁合金的结构类型和Mg（六方相）相同，Gd溶入Mg的晶格形成置换固溶体，组织中存在着Mg24Y5第二相。加入合金化元素Zn后，组织发生较大变化，形成雪花状的枝晶，而且在固溶以及时效处理过程中，其形貌没有消失，只是有所溶解。实验合金GWZ721在砂型铸造工艺条件下热处理后的室温力学性能优良，抗拉强度达到250MPa，屈服强度甚至达到235MPa，远远优于商品镁合金AZ91C（85 MPa）与ZK51 A（140 MPa），而且塑性也比较好，最高达到6.2%。砂型铸造试验合金GWZ721热处理后的高温瞬时拉伸性能也相当优良，在200℃、250℃和300℃时，实验合金的抗拉强度分别达到225MPa、220MPa和205MPa。抗拉强度和屈服强度随着温度的升高均有所下降，但下降不多，延伸率则随着温度的升高有所上升。通过向GW系铸造镁合金添加合金化元素Zn，改善了实验合金GW72的组织，实验合金GW721在保证提高力学性能的前提下降低了成本，是一种较有前途的高端镁合金材料。

The influence of alloying element Zn on the microstructures and properties of GW series sand-cast magnesium alloys was investigated in this paper by using optical microscopy, X-ray diffractometry, scanning electron microscopy. The results show that: the structure type of GW series magnesium alloys was similar to pure magnesium (h.c.p). Gd was resolved in the magnesium alloy. At the same time, Mg24Y5 was also founded in the GW series magnesium alloys. When alloying element Zn was added into the GW series magnesium alloys, the great changes about the microstructures were taken place. The snow-liked form grain formed, and didn’t disappear during the process of annealing, only just resolved in the magnesium alloy. Experimental alloys GWZ721 after Hot-treatment showed the outstanding mechanical properties at room temperature. The ultimate tensile strength reached 250MPa. Moreover, the yield strength reached 235MPa, far better than those of commercial magnesium AZ91C (85MPa) and ZK51A (140MPa). The elongation also reached 6.2% at most. The most important was that Experimental alloys GWZ721 after Hot-treatment also showed the outstanding mechanical properties at elevate room temperature. The ultimate tensile strength at 200℃、250℃and 300℃ was 225MPa、220MPa and 205MPa, respectively. The ultimate tensile strength and the yield strength decreased when the temperature increased, however, the elongation increased in step with the temperature. The microstructures of experimental alloys GW72 was improved when alloying element Zn was added into the GW series magnesium alloys. The cost of experimental alloys GW721 was cut down on the condition that the outstanding mechanical properties were realized. It can conclude that experimental alloys GW721was a kind of promising high-quality magnesium alloys.