Gd对Mg9AlZnY镁合金消失模组织和性能的影响

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

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235 MPa，200 ℃高温抗拉强度为156 MPa，分别比Mg9AlZnY合金提高了11.9%和28.9%

Abstract:

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