微量Gd添加对Mg-8Zn-1Mn-3Sn合金组织转变及性能的影响

Effect of Minor Gd Addition on Microstructure Evolution and Properties of As-cast Mg-8Zn-1Mn-3Sn Alloy

研究了微量Gd的添加对Mg-8Zn-1Mn-3Sn合金显微组织及性能的影响。结果表明,Mg-8Zn-1Mn-3Sn-xGd主要由α-Mg基体、MgZn_(2)、Mg_(7)Zn_(3)、Mg_(2)Sn相、MgSnGd相组成。MgSnGd相为高温相,在合金凝固过程中最先形成,改变了凝固过程,使晶界处半连续第二相转变为断网状。MgSnGd相与α-Mg基体存在共格位向关系,能作为异质形核核心细化合金晶粒。Mg-8Zn-1Mn-3Sn-0.5Gd合金的综合力学性能最佳,合金力学性能得到显著提高的机制为通过添加Gd元素细化晶粒组织、MgSnGd相钉扎晶界阻碍位错运动以及晶界第二相形貌转变。

The effect of minor Gd element on the microstructure and properties of Mg-8Zn-1Mn-3Sn alloy was studied.The results show that Mg-8Zn-1Mn-3Sn-xGd is mainly composed of α-Mg matrix,MgZn_(2),MgZn,Mg_(7)Zn_(3),Mg_(2)Sn phase and MgSnGd phase.The MgSnGd phase is a high temperature phase,which is formed firstly during the solidification and changes the solidification process,causing the semi-continuous second phase at the grain boundary to transform into a discontinuous network.The MgSnGd phase has a coherent orientation relationship with theα-Mg matrix,which can be used as a heterogeneous nucleation core to refine grains.The Mg-8Zn-1Mn-3Sn-0.5Gd alloy has the best comprehensive mechanical properties.The mechanical properties of the alloy are significantly improved by adding Gd elements to refine the grains,and the MgSnGd phase pins the grain boundary to hinder the movement of dislocations and the transformation of the second phase of the grain boundary.