Gd对Mg9AlZnY镁合金消失模组织和性能的影响

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%。

Effects of Gd on Microstructure and Mechanical Properties of Mg9AlZnY Alloy in Lost Foam Casting

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.