Isothermal Section Of Mg-Zn-RE(Re=Gd, Y)Ternary Systems At553K

Abstract:Due to its excellent performance, magnesium-based alloys known as "the green engineering materials of the21st century" have been widely used in many fields, such as automobile, electronic products, aerospace and so on, and become a hot research field of structural materials. In recent years, the quasicrystalline phases discovered in magnesium alloys with rare-earth elements can greatly improve the creep resistance and strength. So the influence of the quasicrystalline phases becomes a hot research field. In order to provide guide for alloy design, the diffusion multiple technique is applied to study on the related system by using electron probe microanalysis (EPMA). The following results have been carried out.(1) Isothermal section of Mg-Gd-Zn system at553K is established by diffusion multiple and electron microprobe micro-analysis (EPMA). W-phase is confirmed a ternary phase, not a solid solution phase of Mg3Gd, which composition is25.2-33.2at.%Mg,25at.%Gd,41.8-49.5at.%Zn. The composition of quasicrystalline phase I is16-25at.%Mg,14-22at.%Gd,55-58at.%Zn, larger than reports. Noticeable solid solution of Zn in the Mg5Gd and Mg3Gd binary compounds occur. According to the backscattered electron images, twelve equilibriums are obtained at553K. They are Mg+Mg5Gd+W, Mg+W+I, Mg+MgZn+I, Mg2Zn3+MgZn+I, Mg2Zn3+MgZn2+I, Mg3Gd+Mg5Gd+W, Gd+MgGd+Mg3Gd, Gd+Mg3Gd+W, Gd+GdZn2+W, I+GdZn2+W, I+GdZn2+MgZn2and GdZn2+GdZn3+MgZn2.(2) Isothermal section of Mg-Zn-Y system at553K is established by diffusion multiple and electron probe microanalysis (EPMA). H-phase is a ternary phase, not a solid solution phase of YZn5, which composition is21.3-33.1at.%Mg,48.4-61.6at.%Zn,16.2-19.8at.%Y. The composition of W-phase is25.8-36.6at.%Mg,41.2-49.2at.%Zn,22.0-26.0at.%Y. The composition of X-phase is75.5-77.5at.%Mg,10-15at.%Zn,10at.%Y, larger than reports. Binary phase Mg2Y has a noticeable solid solution of25.8-33.2at.%Y and1.5-12at.%Zn. Twelve three-phase equilibriums are acquired on the basis of BSE images. They are Mg+Mg24Y5+X, Mg+W+X, Mg+MgZn+W, MgZn+Mg2Zn3+W, Mg2Zn3+W+H, Mg2Zn3+MgZn2+H, MgZn2+YZn2+H, YZn2+W+H, YZn2+Y+W, Mg2Y+Y+W, Mg2Y+Mg24Y5+W and Mg24Y5+W+X.