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采用光学显微镜(OM),场发射扫描电镜(SEM),透射电镜(TEM),X射线衍射分析(XRD)和高温拉伸试验等研究了稀土Nd元素对ECAP态Mg-15Al合金显微组织及高温力学性能的影响。实验结果表明:随着Nd含量的增加,Mg-15Al-x Nd合金平均晶粒尺寸逐渐减小,当Nd含量达到1.5%和4%时,组织中分别出现针状Al11Nd3和不规则块状Al2Nd相。经ECAP挤压四道次后,基体平均晶粒尺寸2~3μm,β-Mg17Al12相显著细化且呈弥散分布状态。稀土Nd元素可以有效改善ECAP态Mg-15Al合金的高温力学性能,当Nd含量为1.5%时,合金在200℃时的屈服强度和抗拉强度由未加Nd时的116 MPa和139 MPa分别提高到148 MPa和172 MPa。ECAP挤压过程中被碎化的高熔点Al-Nd相在高温下对晶界有较强的钉扎作用,表现出显著的细晶强化和弥散强化效果。
The effects of rare earth element Nd on the microstructure of ECAP Mg-15Al alloy and the microstructure of the ECAP Mg-15Al alloy were investigated by optical microscope (OM), field emission scanning electron microscope (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and high temperature tensile test Effect of High Temperature Mechanical Properties. The experimental results show that with the increase of Nd content, the average grain size of Mg-15Al-xNd alloy decreases gradually. When Nd content reaches 1.5% and 4%, Al11Nd3 and Al2Nd phase. After ECAP extrusion for four passes, the average grain size of the matrix was 2 ~ 3μm, and the β-Mg17Al12 phase was significantly refined and dispersed. Rare earth Nd element can effectively improve the high temperature mechanical properties of ECAP Mg-15Al alloy. When the Nd content is 1.5%, the yield strength and tensile strength of the alloy at 200 ℃ increase from 116 MPa and 139 MPa To 148 MPa and 172 MPa. The high melting point Al-Nd phase, which is shredded during ECAP extrusion, has a strong pinning effect on grain boundaries at high temperature and shows remarkable grain refinement and dispersion strengthening effect.