稀土Ce对ZK20镁合金组织与性能的影响

Effect of Ce on microstructure and deformation performance of ZK20 alloy

研究不同含量的稀土元素Ce对ZK20镁合金组织、力学性能以及热变形行为的影响，通过采用常规金相、X射线、SEM、XRD分析，以及常温拉伸和热模拟压缩实验，分析Ce元素在ZK20镁合金中的存在形式及其对合金组织和性能的作用机制。结果表明，在实验范围内（0～0．68％Ce（质量分数，下同）），随着Ce的添加，合金中出现的含Ce合金相r相不断增多，形态向不连续网状及网状转变，合金经热挤压后，Ce元素能改善合金的再结晶程度，晶粒尺寸随Ce添加量的增加不断变小，其中Ce添加量为0．7％的合金挤压态力学性能最佳，其室温抗拉强度为261MPa，屈服强度为198MPa，延伸率为24．6％。280℃×4h的退火工艺能使挤压态合金的强度和塑性提高，其抗拉强度达到272MPa，屈服强度达到209MPa，延伸率为26％。Ce的加入能使ZK20合金由脆性断裂向部分韧窝的混合断裂转变。

The effects of different Ce contents on the microstrueture, mechanical properties and performance of hot deformation were investigated. By methods of OM, X-ray, SEM, XRD, tensile test at room temperature and hot compression test on Gleeble 1500D thermal-mechanical simulator, the mechanism properties of Ce ele ment in ZK20 and its effect on microstrueture were analyzed. The results showed that within the experimental range （0 to 0.68% Ce （mass fraction, the same below））, the phase r were increased with the addition of Ce, the form were changed to the discontinuity mesh and mesh in the alloy by hot extrusion. Ce element could im- prove the recrystallization of the alloy. The grain size continuously decreased with increasing Ce. The extruded alloy exhibted best mechanical properties with the 0.7% addition of Ce. Its room temperature tensile strength was 261 MPa, yield strength was 198 MPa, elongation was 24.6%. Annealing process in condition of 280 ℃ and 4 h could contribute to the strength and ductility of the alloy. Its tensile strength was improved to 272 MPa, yield strength was improved to 209 MPa, and elongation was 26%. The addition of Ce into ZK20 alloy could cause the transition ofbrittle fracture to brittle and dimple mixed fracture.