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采用FactSage热力学软件和镁基数据库计算了Mg-6Zn-1Y合金的凝固路径。利用SEM并配合EDS,XRD,DSC研究了超高压下Mg-6Zn-1Y合金的凝固过程和准晶形成。结果表明:常压下该合金凝固组织主要由粗大α-Mg枝晶和分布在枝晶间含准晶I-Mg3YZn6相的层片状组织等组成,合金凝固过程的实验分析与热力学计算结果吻合较好。Mg-6Zn-1Y合金在GPa级超高压下凝固不但可以获得超细的枝晶组织,还可改善枝晶间层片状组织的形态。随着凝固压力的增加,由常压下的晶间网状或带状逐渐过渡到超高压下的“长岛状”以及“粒状”。特别是提高了单位面积上晶间相(含准晶I-Mg3YZn6相)的含量,其体积分数约占40%,同时还形成了纳米级的弥散分布在基体上高Y含量的Mg-Zn-Y三元新相。
The solidification path of Mg-6Zn-1Y alloy was calculated using FactSage thermodynamic software and magnesium-based database. The solidification process and quasicrystal formation of Mg-6Zn-1Y alloy under ultrahigh pressure were studied by SEM and EDS, XRD and DSC. The results show that the solidification microstructure of the alloy consists mainly of coarse α-Mg dendrites and lamellar structure with quasi-crystal I-Mg3YZn6 phase distributed between the dendrites at atmospheric pressure. The experimental results of the solidification process agree well with those of the thermodynamic calculation better. The solidification of Mg-6Zn-1Y alloy under GPa ultrahigh pressure not only can obtain ultrafine dendrite structure, but also can improve the morphology of dendrite interlamellar lamellar structure. With the increase of the solidification pressure, the transition from the intergranular network or ribbon under atmospheric pressure to the “long island” and “granule” under the ultrahigh pressure. In particular, the content of intergranular phase (including the quasicrystalline I-Mg3YZn6 phase) per unit area is increased, and the volume fraction thereof is about 40%. Meanwhile, a nanoscale Mg-Zn- Y ternary new phase.