基于核壳结构复合相调控的高锂铸造Al-Li-Cu系合金强韧化基础研究

The low mechanical properties of high Li containing cast Al-Li-Cu series alloys hinder their application in aerospace load-carrying components. Through the micro-alloying of Zr and Sc, the composite phase with core-shell structure can be formed in Al-Li alloy, and the co-planar slip can be suppressed. It is an effective way to improve the strength and toughness of cast Al-Li alloy, during which the control of composite phase with core-shell structure is the most critical. Based on this, the Al-3Li-2Cu-xM (M is Zr, Sc or Zr / Sc) alloy is studied in this project. The effects of alloy composition, non-equilibrium solidification conditions and heat treatment process on the size and density of Al3 (Li, M) composite phases with core-shell structure are systematically studied. The interaction mechanism of the three factors on the formation of composite phase with core-shell structure is revealed. The control method of the composite phase with core-shell structure in cast Al-Li alloy is proposed. At the same time, the mechanical properties and casting properties of Al-3Li-2Cu-xM alloy are studied. The contribution of Al3 (Li, M) composite phases with core-shell structure to the strength and toughness of the alloy is proved. The effects of alloy composition and casting process on the casting formability of the alloy are clarified. The results are expected to provide theoretical and experimental basis for the development and application of lightweight high performance cast Al-Li alloy materials in aerospace.

高锂铸造Al-Li-Cu系合金力学性能偏低，阻碍了其在航空航天承力构件上的应用。通过Zr、Sc元素微合金化，可在铝锂合金中形成具有核壳结构的复合相，进而抑制共面滑移，是一种提高铸造铝锂合金强韧性的有效途径，这其中，核壳结构复合相的调控最为关键。基于此，本项目以Al-3Li-2Cu-xM（M为Zr、Sc或Zr/Sc）铝锂合金为对象，系统研究合金成分、非平衡凝固条件和热处理工艺对核壳结构Al3(Li，M)复合相尺寸和数量密度的影响，揭示三者对核壳结构复合相形成的交互作用机制，提出铸造铝锂合金中核壳结构复合相的调控方法；同时，研究Al-3Li-2Cu-xM合金的力学性能和铸造性能，探明核壳结构Al3(Li，M)复合相对合金强韧性的贡献，阐明合金成分和铸造工艺对合金铸造成形性的影响。研究结果可望为航空航天用轻质高性能铸造铝锂合金材料的开发和应用提供理论及实验依据。

为了解决高锂铸造Al-Li-Cu系合金力学性能偏低的难题，本项目提出通过Zr、Sc等元素微合金化，在铝锂合金中形成具有核壳结构的复合相，进而抑制共面滑移，提高铸造铝锂合金强韧性的方法，系统研究了合金成分、非平衡凝固条件和热处理工艺等对核壳结构相形成的作用机制，探究了核壳结构相调控方法及其对合金强韧性的影响。探明了Sc和Zr复合添加对Al-3Li-2Cu和Al-2Li-2Cu铸造铝锂合金微观组织、力学性能及热处理过程中组织演变的影响规律；阐明了冷却速率对金属型和砂型铸造铝锂合金非平衡凝固组织的影响机制；揭示了核壳结构相的形成机制，发现Al3Li粒子在Al3Zr、Al3Sc等Al3M或Al3(M1，M2)弥散相上形核（M为Zr、Sc或Zr/Sc），可以有效降低体系的表面自由能和应变能，进而形成以Al3M或Al3(M1，M2)弥散相为核，Al3Li相为壳的核壳结构复合相；建立了含Sc铝锂合金175℃等温时效过程中核壳结构相的粗化动力学方程；提出了基于多元微合金化和新型热处理工艺协同的核壳结构复合相调控方法；探明了核壳结构复合相对铸造Al-Li-Cu系合金强韧性的作用机制；建立了合金成分、铸造工艺与合金铸造成形性之间的关系，为高性能铸造铝锂合金设计提供了理论指导。在此基础上，开发出力学性能优异的Al-2Li-2Cu-0.5Mg-0.2Zr-0.2Sc铸造铝锂合金，密度小于2.6g/cm3，弹性模量达到80GPa，砂型铸造条件下合金抗拉强度≥450MPa、屈服强度≥350MPa、延伸率≥4%。采用该合金成功研制出铝锂合金壳体样件，其力学性能和内部质量良好，通过了外液压打压检测，在航空航天、水中兵器等武器装备领域应用潜力巨大。发表了标注有本项目号的SCI论文21篇，授权国家发明专利9项，培养博士生4名，硕士生6名。