稀土元素Ce对Al-Cu-Mn-Mg合金显微组织及力学性能的影响

Influence of Ce addition on the microstructure and mechanical properties of Al-Cu-Mn-Mg alloy

摘要:

采用光学显微镜（OM）、扫描电镜（SEM）、透射电镜（TEM）及X射线衍射（XRD）等表征技术研究了微量Ce对Al-Cu-Mn-Mg合金显微组织与力学性能的影响。结果表明:随着Ce含量的增加，合金中会形成两种不同的含Ce化合物，一种是凝固过程中形成的初生Al20Ti2Ce相，该相的出现消耗了铝熔体中有效的晶粒细化元素Ti，导致合金的晶粒粗化。另一种是凝固后期通过共晶反应形成的Al16Cu4Mn2Ce相，该相在高温下不稳定，热处理过程中会转变为Al24Ce3Cu8Mn和Al20Cu2Mn3，无法使Al16Cu4Mn2Ce相中的Cu、Mn元素固溶进入Al基体，导致热处理后合金基体中Cu、Mn元素的过饱和度下降。此外，Ce的添加会延缓铝基体中θ""相向θ"相的转变过程，同等热处理条件下，含Ce合金Al基体中的主要强化相为θ""相。稀土元素Ce对合金相组成及显微组织的影响直接体现在合金力学性能的变化，当Ce含量从0增加至0.3 wt%时，与不含Ce的基础合金相比，0.3Ce合金的抗拉强度和屈服强度分别下降了87 MPa和42 MPa，延伸率下降了50%。

Abstract:

This study systematically investigated the influence of cerium (Ce) additions on the microstructure and mechanical properties of Al-Cu-Mn-Mg alloys through multi-scale characterization techniques including optical microscopy (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD). The results reveal that the addition of Ce leads to the formation of two distinct Ce-containing intermetallic compounds. The first is the primary Al20Ti2Ce phase formed during solidification, which has caused the grain coarsening due to consumption of the effective grain-refining element Ti in Al melt. The second Ce-containing phase is Al16Cu4Mn2Ce, which forms through a eutectic reaction at the final stage of the solidification process. This phase is unstable at high temperatures and undergoes a phase transformation into Al24Ce3Cu8Mn and Al20Cu2Mn3 during heat treatment, it means that Al16Cu4Mn2Ce can not dissolve like Al2Cu, which prevents an increase in the concentration of Cu and Mn in the Al matrix, thereby leading to a low degree of supersaturation. Furthermore, the addition of minor Ce can retard the phase transformaiton from θ"" to θ" in the Al matrix. Therefore, the main strengthening phase is still the θ"" phase in the Ce-containing alloy while θ" phase in 0Ce alloy after the same heat treatment. Changes in the microstructure and phase composition directly affect the mechanical properties of alloys, the ultimate tensile strength and yield strength decrease by 87 MPa and 42 MPa respectively when the Ce content increases from 0 to 0.3 wt%, and the elongation decreases by 50% compared with 0Ce alloy.