Zn固溶量对Mg-Zn-Y合金组织的影响

Effect of Solid Solution Amount of Zn on Microstructure of Mg-Zn-Y Alloy

利用电化学相分离法,成功提取Mg-Zn-Y合金中的第二相,并获得合金元素在Mg-Zn-Y合金中的固溶量,建立了镁合金中直接测定元素固溶量的方法。利用Miedema混合焓模型及Toop模型(对称)和Kohler模型(非对称)计算Mg-Zn-Y三元合金中Zn的活度及活度相互作用系数,通过实验测定及计算表明:Mg-Zn-Y中Zn的自相互作用系数与Y的相互作用系数均为正值,说明这一体系里Zn与Zn,Zn与Y是相互排斥的,Y的存在可以提高Zn的活度,即Y固溶量的增加会导致Zn固溶量的降低,增加了固液界面前沿液相中的成分过冷度,从而使得晶粒细化,晶界处片层状的Mg3Y2Zn3共晶相聚集增多,逐渐连续成网状。

The second phase in Mg-Zn-Y alloy was extracted by electrochemical phase separation, and the solid solution amount of alloying elements in Mg-Zn-Y alloy was obtained. A method for direct determination of solid solution amount in magnesium alloy was established. The activity and activity interaction coefficients of Zn in Mg-Zn-Y ternary alloy were calculated by Miedema mixed enthalpy model and Toop model(symmetry) and Kohler model(asymmetric). The experimental measurements and calculations show that the interaction coefficients of Zn and Y in Mg-Zn-Y alloy are positive, indicating that Zn and Zn, Zn and Y are mutually exclusive in this system. The existence of Y can improve the activity of Zn, and the increase of Y solution amount will decrease the solid solution amount of Zn. Thus, the supercooling degree of the liquid phase in the front of the solid-liquid interface is increased so that the grain is refined, and the Mg3Y2Zn3 eutectic phase of the grain boundary is increased to form continuous mesh gradually.