高强韧稀土镁合金关键承力构件精密塑性成形过程组织演化及强韧化机制

With the demands of the weight-reduction, energy-efficiency and environmental protection in aerospace, aviation and automobile industries, the lightweight components have been becoming an important research field recently. The developments and applications of rare earth magnesium alloys with high strength close to the strength of the aluminum alloys are attracting more attentions around the world due to the demands of the magnesium alloys components with especially high strength. The magnesium alloys are difficult to deform because of the hexagonal close packed crystal lattice which is also ascribed to the poor ductility of the alloys. Furthermore, the rare earth elements segregate easily in the rare earth magnesium alloys during the cast process, which results in the uneven as-cast microstructure and more difficulties during the plastic deformation and subsequent annealing process. Specially, the strength of the forgings with large size is usually very low due to the above reasons and it is difficult to obtain the precision control on the relationships between the microstructure and mechanical properties of the alloys, which seriously limits the wide applications of the key load bearing components. The technologies of the initial forging, isothermal precision forging and subsequent annealing processes are investigated in the project.The strengthening and toughing mechanisms are also discussed in details and the comprehensive control on the relationships between microstructure and mechanical properties is realized. The results of the project have a great important effect on the strengthening and toughing measures of the rare earth magnesium alloys and can meet the urgent demand in key load-bearing components with lightweight and high strength in aerospace and aviation fields.

为了满足航空、航天和汽车等领域对于减重、节能和环保的迫切需求，构件轻量化成为一个重要的发展方向，对于轻质、高强镁合金构件的需求日益增加，特别是强度和韧性接近于中高强铝合金的高强韧稀土镁合金的开发和应用最为引人关注。由于镁合金具有密排六方结构，其塑性变形能力差，被认为是一种难以塑性加工的金属材料，而稀土元素的加入又会导致镁合金在铸造过程中易于形成偏析，造成大型稀土镁合金铸锭组织成分不均匀，使得随后的铸锭开坯、塑性加工和热处理工艺更加困难，导致大型稀土镁合金锻件的强韧化效果不明显，很难实现其组织结构和性能的精确调控，大大限制了稀土镁合金作为大型关键承力构件的应用。本项目拟开展高强韧稀土镁合金关键承力构件开坯、锻造和热处理工艺的研究，揭示稀土镁合金的强韧化机制，实现高强韧稀土镁合金构件的组织性能一体化协调控制，满足高强韧稀土镁合金大型关键承力构件在航天、航空领域的迫切需求。

项目针对航天、航空领域轻量化的迫切需要，以高强韧稀土镁合金大型关键承力构件为对象，开展高强韧稀土镁合金锻造开坯、等温精密成形和热处理工艺的研究，获得高强韧稀土镁合金在锻造开坯、等温精密成形和热处理工艺过程中的组织演变规律，揭示稀土增强型镁合金的强韧化机制，实现高强韧稀土镁合金构件的组织性能一体化协调控制，拓展高强韧稀土镁合金大型关键承力构件在航天、航空领域应用。. 项目执行过程中围绕上述研究目标，进行了不同开坯方法、开坯温度、变形速度和变形量等工艺参数对稀土镁合金开坯缺陷影响的研究；完成了稀土镁合金支架和转接头等温精密成形过程的有限元模拟，开展了稀土镁合金支架和转接头等温精密成形实验，研究了温度、应变速率和变形程度等工艺参数对支架和转接头两种不同类型锻件充填质量和成形精度的影响规律，并完成了不同热处理工艺参数对稀土镁合金锻件组织性能影响的研究；揭示了开坯、等温成形和后续热处理等不同阶段稀土镁合金锻件中晶粒尺寸和析出相等微观组织结构演化规律，进行了稀土镁合金关键承力构件的力学性能测试和分析；建立了稀土镁合金强韧化模型，实现了高强韧稀土镁合金构件的组织性能一体化协调控制，并研制了承力构件试验样件。. 项目完成了预定的研究目标，已发表学术论文10篇，其中Sci收录6篇，获得授权国家发明专利1项，申请国家发明专利1项。项目负责人单德彬教授2013年入选国家“百千万人才工程”，2014年入选教育部长江学者特聘教授。先后培养博士生1名，硕士生5名。