铸造Mg-7Sn-2Al-xBi合金的组织与性能研究

Study on Microstructure and Properties of Cast Mg-7Sn-2Al-xBi Alloys

使用光学显微镜、扫描电子显微镜、能谱仪、X射线衍射仪、显微硬度计和材料试验机研究了铸态Mg-7Sn-2Al-x Bi(x=1,2,3wt%)合金的微观组织和力学性能,讨论了Bi对合金组织和性能的影响。结果表明,Bi能使铸态合金的晶粒得到细化,当Bi含量为2wt%时,晶粒细化效果最佳。铸态组织由α-Mg、Mg_(2)Sn和Mg_(3)Bi_(2)相组成,Bi能促进Mg;Sn相析出和增加Mg;Bi;的数量。但Bi含量为3wt%时,Mg_(2)Sn相有所长大。随着Bi含量的增加,合金的硬度和压缩强度提高,而塑性在Bi含量为3wt%时明显下降。适量的Bi合金化有助于细化Mg-7Sn-2Al铸态合金的组织,显著提高合金的强度并保持较好的塑性。

The microstructure and mechanical properties of the as cast Mg-7Sn-2Al-xBi (x=1,2,3wt%) alloys were investigated by using optical microscope,scanning electron microscope,energy dispersive spectrometer,X-ray diffractometer,micro-hardness tester and materials testing machine.The effect of Bi element on the microstructure and mechanical properties of the alloy was discussed.The results show that Bi can refine the grains of the cast alloy,and grain refinement effect is the best when Bi is 2wt%.The casting microstructure consists ofα-Mg,Mg_(2)Sn and Mg_(3)Bi_(2) phases.Bi can promote the Mg_(2)Sn phase precipitation and increase the number of Mg;Bi;phase.But when the Bi content is 3wt%,the Mg_(2)Sn phase grows up.With the increase of Bi content,the hardness and compressive strength of the alloys improves,while the plasticity decreases significantly at the Bi content of 3wt%.Appropriate Bi alloying helps to refine the microstructure of the Mg-7Sn-2Al cast alloy,significantly improve the strength of the alloy and maintain good plasticity.