基于电弧增材非平衡凝固效应Al-Ce耐热合金组织性能调控机理研究

金属间化合物增强Al-Ce合金因组织热稳定性高、耐热性能优异，是制造高超音速导弹主结构蒙皮的重要候选材料。然而受近平衡凝固限制，常规铸造Al-Ce合金组织粗大，Al11Ce3增强相含量有限且形成复杂棱面相形态，造成合金强度较低且延展性不足。为解决此瓶颈难题，本项目拟利用电弧增材制造技术，探索热输入最小化与非平衡凝固效应最大化实现方法，研究以非平衡凝固效应为核心的显微组织主动调控机理；分析晶粒尺寸与共晶间距超细化机制，揭示高Ce含量合金初生相Al11Ce3与共晶相、层片状与纤维状共晶竞争生长规律，厘清组织特征尺寸超细、增强相体积分数高、完全纤维状共晶组织形成机理；阐明凝固工艺、显微组织与力学性能的内在联系，实现力学性能提升。本项目旨在利用Al-Ce合金与电弧增材制造的高度匹配性与互补性，基于非平衡凝固组织调控，同步实现合金快速制造与高效控性，为大马赫数导弹主结构蒙皮的研制提供理论和技术支撑。

Owing to the excellent microstructure thermal stability and heat resistance, the intermetallics strengthened Al-Ce alloys are of great potential for fabricating large-scale and complex hypersonic missile structural skins. However, as a result of near-equilibrium solidification and faceted growth of intermetallic Al11Ce3, conventional cast Al-Ce alloys form coarse-grained and complex microstructures, with insufficient volume fraction of Al11Ce3. Such alloy microstructures produce unfavorable mechanical properties. To address this bottleneck issue, we conceive of microstructure tuning for Al-Ce alloys via wire arc additive manufacturing (WAAM), a non-equilibrium solidification pathway. The method to minimize processing heat input and maximize non-equilibrium solidification effect will be explored, as well as the microstructure refinement mechanism, including grain size and Al11Ce3 phase size. The growth behaviors of primary Al11Ce3 and eutectics will be investigated to reveal the phase selection mechanism. We will also focus on the competitive growth of fibrous and lamellar eutectics, and eventually, an untra-fined fibrous eutectic microstructure with a higher volume fraction of intermetallic Al11Ce3 is expected. The improvements in the strength and ductility of Al-Ce alloys can thus be achieved via above microstructure optimization, based on the inherent relationship among WAAM process, microstructure feature and mechanical performance. A breakthrough on the rapid-near-net-shaping of Al-Ce alloys with desired mechanical performance can thus be achieved, based on the optimization of non-equilibrium solidification microstructures. Theoretical and technical support can be provided on the development of structural skins for large-Mach hypersonic missiles.