中文摘要：

在Mg9AlZnY合金基础上添加不同含量Gd元素,采用消失模铸造成形,研究其组织性能变化。结果发现,随着Gd含量的增加,Mg9AlZnY合金中的β-Mg17Al12相形成数量显著减少,并由连续网状结构转变为断续状和颗粒状结构。含Gd的Mg9AlZnY合金组织主要由α-Mg固溶体、β-Mg17Al12相和分布在α-Mg晶界的少量棒状Al2Y相和块状Al2Gd相组成。Al2Y和Al2Gd相热稳定性好,在高温下对晶界具有钉扎作用,防止晶界滑移,提高了晶界的高温强度。当Gd含量在0.9%（质量分数）左右时,经T6热处理后室温的抗拉强度为235MPa,200℃高温抗拉强度为156MPa,分别比Mg9AlZnY合金提高了11.9%和28.9%。

英文摘要：

Microstructures and mechanical properties of the Mg9AlZnY magnesium alloy in lost foam casting were researched through adding rare-earth element Gd. The results show that the β-Mg17Al12 phase of Mg9AlZnY alloy is significantly reduced with the increase of Gd element,and the formation of β-Mg17Al12 phase turns into an intermittent and granular structure from the continuous network structure. Microstructure of the Mg9AlZnY alloys containing Gd is mainly composed of the α-Mg solid solution,β-Mg17Al12 phase and a small number of rod-like Al2Y and block-like Al2Gd phases which are distributed over grain boundaries of the α-Mg phase. The Al2Y and Al2Gd phases,which pin the grain boundary at high temperature and prevent grain boundary from sliding,have good thermal stability,increasing the high-temperature strength of the grain boundary. After T6 heat treatment,the tensile strength at room temperature is 235 MPa and the high-temperature strength at 200 oC is 156 MPa when the rare-earth element Gd is about 0.9%,which is increased by 11.9% and 28.9% compared with those of Mg9AlZnY alloy,respectively.