稀土镁合金损伤在线渐进修复/交叉旋压耦合强化方法和机理

RE containing magnesium alloys show great potential in aviation, aerospace and weapon fields due to high specific strength, low density and good thermal stability. The thin-walled rotary workpieces of Mg alloy can be produced preferentially by spin forming process, but the poor spinnability, the initiation and propagation of microscopic damage during power spinning lead to the low mechanical properties of as-spun workpieces of Mg alloys. In terms of three typical RE containing Mg alloys (MB26、Mg-RE、Mg-Zn-RE), the project is proposed to study the coupled strengthening method and mechanism of on-line progressive damage healing and reciprocating spinning. The main content includes: 1) Formation mechanism, evolution law of microscopic damage and crack control during hot power spinning of Mg-RE alloys; 2) On-line progressive healing process and mechanism of spinning damage by means of induction eddy current pulse; 3) Evolution and prediction of microstructure and texture and its influence on mechanical properties during reciprocating spinning process; 4) Controlling of microstructure and mechanical properties during hot power spinning by the coupling treatment of reciprocating spinning and induction eddy current pulse. This study puts forward a new method of damage healing by eddy current pulse as well as a novel technology of texture control by reciprocating spinning. Through solving the bottleneck problem by coupling the two processes, the theoretical method and process routine will be established to realize the manufacture and promote the application of as-spun thin-walled workpieces of RE containing Mg alloys with high mechanical properties.

稀土镁合金以其高比强度、低密度和良好的热稳定性在航空航天和武器装备领域具有广阔的应用前景，其薄壁回转体构件采用旋压成形具有独特优势。但是稀土镁合金存在可旋性差、细观损伤萌生和扩展等难题，使得其旋压件性能偏低。为此，本项目以稀土镁合金（MB26、Mg-RE、Mg-Zn-RE）为对象，开展损伤在线渐进修复和交叉旋压耦合强化方法和机理研究，主要包括：1）镁合金热强旋过程细观损伤产生机制、损伤演化规律及裂纹控制；2）基于脉冲感应涡流处理的旋压细观损伤在线渐进修复方法和机理；3）交叉旋压过程显微组织和织构演化、预测及性能相关性；4）基于交叉旋压和脉冲涡流耦合处理的热强旋过程组织性能调控。该研究提出了稀土镁合金旋压损伤的脉冲涡流修复新方法和变形织构的交叉旋压调控新技术，拟通过二者的耦合作用突破稀土镁合金热强旋瓶颈问题，建立稀土镁合金热旋压强化理论方法和工艺路线，实现高性能镁合金薄壁旋压件的制造和应用。

镁合金是最轻的金属结构材料之一，推动高性能镁合金薄壁构件的应用是实现航空航天和武器装备材料轻质化和结构轻量化最为有效的途径之一，而旋压工艺是制备薄壁回转体构件最为有效的制造技术。然而，由于稀土镁合金塑性差及热加工温度窗口窄等问题，使得镁合金热旋压仍然存在较大困难。本项目针对稀土镁合金旋压过程中的瓶颈问题，以典型Mg-Gd-Y(-Zn)-Zr稀土镁合金为研究对象，开展了稀土镁合金损伤在线渐进修复/交叉旋压耦合强化方法与机制研究。本项目首先建立了稀土镁合金高温损伤模型，实现了对稀土镁合金在不同热变形条件下损伤演化行为和再结晶程度的统一预测。基于建立的热损伤本构模型，实现了对稀土镁合金在热旋压过程中的组织及损伤演化规律的模拟，揭示了旋压过程的损伤断裂机制为随着减薄率的增加，内层应力三轴度逐渐高于外层，导致损伤从外层逐步向内层累积，从而诱发最终断裂。其次，搭建了镁合金旋压件的脉冲电涡流细观损伤修复装置，利用有限元仿真分析和脉冲电涡流处理试验，不仅实现了对稀土镁合金旋压件内部微裂纹的有效修复，并揭示了电脉冲涡流处理对镁合金旋压件内部微裂纹修复的作用机制主要为脉冲电涡流作用产生的裂纹尖端热应力主导下的裂纹愈合效应,而洛伦兹力引起的切向收缩力也促进了裂纹愈合。再次，通过热强旋实验探索出了合理的稀土镁合金热旋压成形工艺参数，有效控制了旋压裂纹的产生，并揭示了稀土镁合金的交叉旋压强化机制为交叉旋压导致的基面织构弱化，使得其力学性能相对于单向旋压有所提高。最后，通过强力热旋压与脉冲电涡流处理耦合作用，实现了稀土镁合金旋压件内外层组织的均匀细化，并促进了内部微观裂纹的修复和愈合，显著提高了稀土镁合金旋压件的力学性能。该研究为稀土镁合金薄壁回转体构件的精密制造及服役过程中的高效低成本修复和改性提供了有效解决方法，有广阔的应用前景。