Zr对铸态Mg-6Bi合金微观组织和力学性能的影响

Effects of Zr on the Microstructure and Mechanical Properties of As-Cast Mg-6Bi Alloy

为探清Zr元素对Mg-6Bi合金微观组织与力学性能的影响规律,制备了铸态Mg-6Bix Zr(x=0,0.5,1.0wt.%)合金,采用SEM、EDS、XRD和电子力学试验机等仪器设备对其微观组织和力学性能进行表征和测试。试验结果表明,铸态Mg-6Bi合金微观组织中树枝晶平均尺寸约为(302±46)μm,且晶界处存在大量尺寸在1~90.12μm之间的Mg3Bi2相。采用0.5%~1.0%Zr元素合金化不但可以显著细化Mg-6Bi合金晶粒组织,还对合金中的Mg3Bi2相有显著地变质效果。其中,Mg-6Bi-1Zr合金平均晶粒尺寸为(128±65)μm,Mg3Bi2相尺寸在1~28.33μm之间,较Mg-6Bi合金均有显著细化。归因于晶界强化和第二相强化效果的增强,以及Mg3Bi2相对基体割裂作用显著削弱,铸态Mg-6Bi合金的强度和塑性均随着Zr元素含量的增加而显著提升。

In order to reveal the influence of Zr alloying on the microstructure and mechanical properties of Mg-6Bi alloy,as-cast Mg-6Bi-xZr(x=0,0.5,1.0 wt.%)alloys were prepared,and their microstructure and mechanical properties were characterized and tested by SEM,EDS,XRD and electronic mechanical performance testing machine.The experimental results showed that the average grain size of the as-cast Mg-6Bi alloy microstructure was about(302±46)μm,and there were a large number of Mg3Bi2 phase with a size between(1-90.12)μm at the grain boundary.The 0.5%-1.0%Zr element alloying can not only significantly refine the grain structure of Mg-6Bi alloy,but also has a significant refinement effect on the Mg3Bi2 phase in the alloy.Among them,the average grain size of Mg-6Bi-1Zr alloy was(128±65)μm,and the phase size of the Mg3Bi2 was between(1-28.33)μm.Both the strength and the ductility of as-cast Mg-6Bi alloy significantly increased with the increase of Zr element content,due to the enhancement of grain boundary strengthening and second phase strengthening effects,as well as the significant weakened cleavage effect original from coarse Mg3Bi2 particles.