Mg-Bi合金的显微组织和力学性能

采用挤压铸造和挤压变形工艺制备了Mg-Bi二元合金,通过金相显微镜分析,室温拉伸性能测试,X射线衍射分析,SEM和EDS等手段,研究了Mg-Bi合金在铸态和热挤压态的显微组织和力学性能.结果表明:铸态Mg-Bi合金随着Bi含量的增加,伸长率逐渐降低,抗拉强度逐渐增加,当Bi含量达10wt.％以上,抗拉强度降低；Mg-Bi合金铸锭经450℃、3h保温,挤压比为12.76热挤压后,随Bi含量的增加,抗拉强度与伸长率均逐渐增加,当Bi含量达12wt.％时,抗拉强度为219.68 MPa,伸长率为13.43％,Bi含量继续增加,合金抗拉强度及伸长率呈下降趋势；挤压态Mg-Bi合金的力学性能是晶粒细化与Mg3Bi2综合作用的结果,当Bi含量大于12wt.％后,形成较多粗大的Mg3Bi2相是导致合金力学性能下降的主要原因.

Microstructure and Mechanical Properties of Mg-Bi Alloys

Mg-Bi binary alloys are prepared by squeezing casting and extrusion deformation,and their microstructures and mechanical properties under as-cast and as-extruded conditions are investigated by optical microscopy(OM),tension test at room temperature,X-ray diffraction(XRD),scanning electron microscope(SEM)and energy dispersive spectrometer(EDS).The results show that the elongation of as-cast Mg-Bi alloy reduces and the ultimate tensile strength increases gradually with the increase of Bi content,while the content of Bi reaches up to 10wt.%,the ultimate tensile strength of alloy starts to reduce.After extrusion at 450 ℃ for 3 h with extrusion ratio 12.76,the ultimate tensile strength and the elongation of Mg-Bi alloy increase gradually with the increase of Bi content,when the content of Bi is up to 12wt.%,it’s ultimate tensile strength is 219.68 MPa,the elongation is 13.43%.The mechanical properties of as-extruded Mg-Bi alloys depend on grain refinement and the strengthening of Mg3Bi2 phase.When the content of Bi is up to 12wt.%,the mechanical properties of alloy reduce due to the formation of many coarse Mg3Bi2 phases.