离心铸造Mg-Zn-Y-Zr合金的显微组织与力学性能

Investigation of Microstructure and Mechanical Properties of Centrifugal Casting Mg-Zn-Y-Zr Alloy

采用离心铸造法和金属型重力铸造法制备了Mg-6wt%Zn-1wt%Y-0.5wt%Zr(简写为ZW61,下同)合金,比较了合金的铸态显微组织及力学性能。结果表明,离心铸造镁合金的晶粒组织得到明显细化,力学性能得到显著提高。利用扫描电子显微镜(SEM)、X射线衍射仪(XRD)研究了ZW61合金的显微组织相组成,基体相均为α-Mg相,ZW61合金的第二相由I相(Mg3Zn6Y)和W相(Mg3Zn3Y2)组成。根据ImageJ软件分析,离心铸件第二相的面积分数比金属型铸件的小,离心铸造中共晶转变L→α-Mg+W和共析转变L+W→α-Mg+I被抑制,导致I、W相减少,形成以过饱和初生相α-Mg为主的凝固组织。离心铸件的塑性特征优于金属型铸件。

Mg-6wt%Zn-1wt%Y-0.5wt%Zr（ZW61） alloy was prepared by centrifugal casting and metal mould casting respectively.The as-cast microstructure and mechanical properties of the alloys were compared.The results show that the microstructure of centrifugal casting magnesium alloy is significantly refined,and its mechanical properties are improved.The microstructure and phase composition of ZW61 alloy were investigated through SEM and XRD.It was found that the matrix phase of both the alloys is α-Mg phase,and the second phase of ZW61 alloy are composed of I-phase（Mg3Zn6Y） and W-phase（Mg3Zn3Y2）.According to the ImageJ software analysis,the area fraction of the second phase in the centrifugal casting alloy is lower than that in the metal mould casting alloy.In centrifugal casting process,the eutectic t ransformation of L → α-Mg ＋ W and eutectoid transformation of L＋ W→ α-Mg ＋ I were suppressed,leading to the reduced amount of I-phase and W-phase,and form a solidification microstructure with the saturated primary phase consisting mainly of α-Mg phase.The centrifugal casting alloy has more plastic features than the metal mould casting alloy.