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τ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261 MPa,屈服强度为198 MPa,延伸率为24.6%。280℃×4 h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272 MPa,屈服强度达到209 MPa,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 microstructure,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 microstructure were analyzed.The results showed that within the experimental range (0 to 0.68% Ce (mass fraction,the same below)),the phaseτwere 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 of brittle fracture to brittle and dimple mixed fracture.
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