控制挤压比制备的AZ91异构镁合金的组织与力学性能

Microstructure and Mechanical Properties of Heterogeneous AZ91 Magnesium Alloy Prepared by Controlling Extrusion Ratio

以商业热轧态AZ91厚板为实验用材料,通过控制挤压比制备了具有异质结构和均匀结构的AZ91棒材,采用光学显微镜(OM)、扫描电子显微镜(SEM)、电子背散射衍射(EBSD)及万能试验机研究了其微观组织与拉伸性能。结果表明:相比于原始热轧态(R)和轧制退火态(RA),挤压后的合金(AE7、AE11、AE17和AE26,数字为挤压比)的强度和塑性均大幅提高。其中,AE7为晶粒较为细小的均匀组织,并具有最高的抗拉强度及屈服强度,但塑性最差;而AE26则呈现晶粒较为粗大的均匀组织,并具有最佳的塑性,但强度最低;AE11和AE17则呈现粗、细晶混合的异质结构,其中AE11表现最佳的强韧结合,这不仅归因于细晶强化和晶粒的硬取向,而且异质变形诱导(HDI)强化和硬化在变形过程中也扮演了重要角色。

AZ91 bars with heterogeneous or uniform structure were prepared by controlling the extrusion ratio,using commercial hot-rolled AZ91 as experimental materials.The microstructure and tensile properties of the bars were studied by optical microscope(OM),scanning electron microscope(SEM),electron backscattering diffraction(EBSD)and universal testing machine.The results show that the strength and ductility of the extruded alloy(AE7,AE11,AE17 and AE26)are significantly improved,compared with the original rolled(R)and rolled annealed(RA)alloy.In addition,AE7 presents a uniform fine-grain structure with the highest strength but the worst ductility,while AE26 obtains a uniform coarse-grain structure with the highest ductility but the lowest strength.Differently,AE11 and AE17 show heterogeneous structure with a mixture of coarse and fine grains,and AE11 has the best combination of strength and ductility,which is not only attributed to the fine grain strengthening and hard orientation of grains.Also,the heterogeneous deformation induced(HDI)strengthening plays an important role in the deformation process.