合金元素与晶体取向协同增强ZK60镁合金强度与阻尼性能及机理研究

The effects of alloy element and crystal orientation on the strength and damping capacity of ZK60 magnesium alloy will be studied systematically in this project. The alloy elements Y and Gd with different chemical compositions will be added into the ZK60 magnesium alloy in orderto investigate the strengthening mechanism and damping behavior. The polycrystalline samples of the ZK60-Y-Gd magnesium alloys with different initial microstructures and crystal orientations will be obtained by means of different plastic deformation mode (including unidirectional and cross rolling, hot extrusion and multidirectional forging) and subsequent annealing treatment. The mechanical properties and deformation characteristics will be studied using Instron and Gleeble apparatus. The microstructure characteristics and phase constitution of the ZK60-Y-Gd magnesium alloys will be examined by optical microscopy (OM), scan electron microscopy (SEM) with electron back scattering diffraction (EBSD), transmission electron microscopy (TEM，including high resolution transmission electron microscopy, HRTEM), X-ray diffraction (XRD) and energy dispersive spectroscopy (EDS). The crystal orientations will be analyzed by orientation distribution function (ODF), pole figure(PF) and inverse pole figure (IPF) with series expansion method. The effects of strain amplitude, temperature and frequency on damping behavior will be investigated by the application of dynamical mechanical analysis (DMA). Taking into account of effects of the alloy element and the crystal orientation simultaneity, the enhancement mechanism of strength and damping capacity of the ZK60-Y-Gd magnesium alloys will be analyzed in detail on the basis of the microscopic crystal plasticity of theory and Granato and Lücke theory. At the same time, the possible plastic deformation mechanisms such as basal slip and nonbasal prismatic slip will be revealed under different deformation conditions. Through this investigation, the enhancement mechanism of alloy element and crystal orientation to the strength and damping capacity will be illustrated explicitly. The obtained results may help us understand mechanical properties and damping behavior of magnesium alloys better, which is very important for the design and fabrication of magnesium alloys with high strength and high damping capacity.

本项目以ZK60变形镁合金为研究对象，基于合金元素增强镁合金强度和微观晶体塑性理论，拟从材料成分设计和加工制备技术两方面着手，通过添加Y、Gd等合金元素和调节晶体取向等微观组织结构特征，探索合金强化和几何硬化协同增强镁合金强度与阻尼性能的途径。基于现代先进的微观组织观察和晶体取向表征分析技术，结合理论分析和计算机模拟，研究外在加工条件和内在材料属性对镁合金强度与阻尼性能的影响规律及相关机理。研究合金元素Y、Gd对ZK60镁合金基体与微观组织缺陷的影响规律，探索强化相析出行为及控制方法；探明合金元素与晶体取向影响镁合金强度与阻尼性能的物理本质。考虑晶体取向因素，建立强化相作用条件下内耗产生与控制模型，探索和开发高强高阻尼镁合金的成分设计与制备、加工及成形等综合性能优化方法。项目的完成将拓展镁合金在我国国防军工和民用工业等高新技术的应用领域，对保障国家安全和促进国民经济发展产生重要推动作用。

本项目以ZK系列镁合金为研究对象，遵循材料成分-工艺-组织-性能相关性原理，从材料成分设计和加工制备技术两方面着手，通过添加Y、Gd等合金元素和调节晶体取向等微观组织结构特征，获得具有不同化学成分、原始组织和初始晶粒取向的镁合金，探索合金强化和几何硬化协同增强镁合金强度与阻尼性能的途径。项目重点以Mg-6.75Zn-0.57Zr-0.4Y-0.18Gd（wt.%）、Mg-4.7Gd-3.4Y-1.2Zn-0.5Zr(wt.%)、Mg-5.5Gd-4.4Y-1.1Zn-0.5Zr(wt.%)、Mg-6.9Gd-3.2Y-1.5Zn-0.5Zr(wt.%）为研究对象，同时将工作拓展至Mg-Al-Zn和Mg-Gd-Y-Zr系列合金。基于微观晶体塑性理论和Granato-Lücke位错钉扎-脱钉模型，结合现代先进的微观组织结构观测（OM、SEM-EBSD、TEM、HRTEM、HAADF-STEM等）和晶体取向表征分析技术（PF、IPF），系统研究了外在加工条件（变形方式、变形条件、热处理制度等）和内在材料属性（化学成分、组织形貌、晶体取向等）对镁合金微观组织、力学性能与阻尼性能的影响规律及相关机理。重点研究了合金在挤压、锻造、环形轧制及时效过程中微观组织演变及合金的强韧化机制；阐明了动态析出相、不同形貌长周期堆垛程有序LPSO相对合金再结晶行为的影响规律；探索了微量Ag元素的添加对Mg-Gd-Y-Zr及Mg-Al-Zn合金时效硬化行为的影响，提升了硬化效果。项目的完成为镁合金在国防军工如航空航天领域的实际应用奠定了良好基础，同时有望拓展其在交通运输等领域的应用。在本项目及其他项目共同资助下，相关内容和结果在国内外学术期刊发表标注有本项目资助的国外期刊32篇、国内期刊5篇（第一标注12篇，第二标注24篇、第三标注1篇），包括1篇《Scripta Materialia》、2篇《Metall. Mater. Trans. A》、1篇《Mater. & Design》、10篇《Mater. Sci. Eng. A》、4篇《J. Alloys & Compd》.、6篇《Mater. Character.》，被SCI收录31篇。授权未标注项目资助的国家发明专利10项，2017年获有色金属工业协会科学技术奖（发明）一等奖。培养完成的学位论文标注本项目资助的毕业博士生4名、硕士生3名。