Zr微合金化对稀土镁合金微观结构和力学性能影响的电子显微学研究-中国材料进展

文章信息/Info

Title:: Atomic Resolution Study on the Effect of Zr Minor Addition on the Microstructure and Mechanical Properties of a Magnesium Alloy

作者:: 王威振; 周信哲; 杨志卿; 叶恒强; （1. 中国科学院金属研究所沈阳材料科学国家研究中心，辽宁沈阳 110016）（2. 季华实验室，广东佛山 528200）

Author(s):: WANG Weizhen1; 2; ZHOU Xinzhe1; YANG Zhiqing2; YE Hengqiang2; (1. Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Science,Shenyang 110016, China) (2. Ji Hua Laboratory, Foshan 528200, China)

Keywords:: magnesium alloys; microstructure; microalloying; strengthening; transmission electron microscopy

摘要:: 微量Zr的添加不仅能够细化镁合金的晶粒，改善铸造性能，还会影响镁合金在热处理过程中微观结构的演变。利用多种电子显微学技术系统研究了Zr微合金化影响Mg-Zn-Nd镁合金力学性能和微观结构演变的机理。研究表明，含有微量Zr的Mg-2.7Nd-0.6Zn-0.5Zr镁合金经798 K固溶处理后，大量纳米Zn-Zr相的析出显著提升了该合金的显微硬度。在系列微束电子衍射分析的基础上，结合多方向原子分辨率结构和成分分析，确定了这些纳米Zn-Zr相为简单四方结构的Zn2Zr3相（空间群：P42/mnm，a=b=0.761 nm, c=0.682 nm），并重构出其原子构型。此外，研究结果还表明固溶处理过程中形成的纳米尺寸Zn2Zr3相，降低了基体中Zn元素的含量，显著提升了强化效果较好的柱面析出相β1-Mg3Nd的比例，进而提高了合金峰时效后的强度。研究结果丰富了Zr影响镁合金微观结构和力学性能机理的研究。

Abstract:: The effect of Zr addition on microstructures and their evolution during heat treatments of a kind of Mg-Zn-Nd alloy was studied using various electron microscopy techniques. The minor addition of Zr not only provid heterogenous nucleation sites to refine grain sizes of Mg during solidification, but also influence microstructural evolution upon solution treatment and aging. Zn2Zr3 precipitates were formed in Mg-2.7Nd-0.6Zn-0.5Zr (wt%) during solution treatment at 798 K, inducing remarkable hardness increment of the alloy. The atomic structure of nanometer Zn-Zr precipitates is determined by combining tilt series of micro-beam electron diffraction with atomic resolution imaging and chemical measurement. The stoichiometry of the Zn-Zr precipitates is Zn2Zr3 with a primitive tetragonal structure (space group P42/mnm, a=b=0.761 nm, c=0.682 nm). Moreover, decrease in Zn concentration in Mg matrix due to the formation of Zn2Zr3 precipitates increased the density ratio of β1-Mg3Nd prismatic rod precipitates to γ″-Mg7(Nd, Zn)3 basal plates in peak aged samples. Our results may shed light on optimization of microstructures and mechanical properties of Mg alloys with Zr addition. Our present finding shed new light on the role of Zr micro-alloying in microstructures and mechanical properties of Mg alloys.