微纳双尺度颗粒增强钛基复合材料热变形行为及协同作用机制

Titanium matrix composites have potential application prospects in aerospace and automotive manufacture due to their low density, high specific strength and excellent high temperature properties. However, low ductility and high high-temperature deformation resistance of titanium matrix composites limit their large-scale engineering applications. While the nano-sized particles can refine the grain size and improve the strength and ductility, simultaneously. In this project, it is hoped to obtain the bimodal size particles (micro+nano-meter) reinforced high temperature titanium alloy matrix composite with fine grains and excellent mechanical properties fabricated by multi-directional forging (MDF) under optimized deformation process. By analyzing the effect of the bimodal size particles on the microstructure (grain and substructure) and mechanical properties, the dynamic recrystallization behavior, high temperature behavior mechanism and strengthening mechanism can be revealed, and the relation of deformation, microstructure and mechanical properties can be constructed as well. Currently, the related systematic research is rather less. This study will have important theoretical value on the control of microstructure and mechanical properties, development and application of titanium matrix composites.

基于轻质高强和优良的高温性能优势，钛基复合材料在航空航天及汽车制造等领域极具发展前景。但铸态钛基复合材料塑性差、变形抗力大，限制了其应用。纳米颗粒可细化晶粒，同时提高材料的强度和塑性。本课题提出在高温钛合金中生成微纳双尺度增强颗粒(微米TiB+纳米Y2O3)，优化热加工工艺参数，采用多向锻造技术制备出晶粒细小、力学性能优良的微纳双尺度颗粒增强钛基复合材料。深入分析微纳双尺度颗粒对基体钛合金的晶粒、亚结构等微观组织和力学性能的影响规律，揭示微纳双尺度钛基复合材料的动态再结晶行为、高温变形机制和强化机理，进一步构建微纳双尺度钛基复合材料的形变、微观特性与力学性能的相关性。目前，国内外相关研究较少，本课题研究将为钛基复合材料的组织性能调控、开发与应用提供理论支持。

颗粒增强钛基复合材料具有高比强度、良好的抗腐蚀、抗氧化性及优异的高温蠕变抗力，因而被认为是航空航天领域重要的候选材料。但铸态钛基复合材料塑性差、变形抗力大，限制了其应用。为此，本研究将原位合成技术与传统铸造法相结合制备了不同体积分数的双尺度颗粒(微米TiB和纳米Y2O3)增强钛基复合材料(其基体为新型近α高温钛合金)。研究了双尺度颗粒含量对铸态近α高温钛合金组织性能的影响规律，阐明了双尺度颗粒增强复合材料的凝固路径，揭示了初生β晶粒及α片层的细化机制，优化了双尺度颗粒含量。基于热力模拟实验，研究了复合材料的热压缩变形行为，揭示了流变应力与变形温度和应变速率之间的关系，并建立了其本构方程。阐明了复合材料在不同变形量、不同温度和不同应变速率下的组织演变规律。基于动态材料学模型，构建了复合材料的热加工图进而阐明了其高温变形机制。在热加工图基础上，研究了多向锻造工艺参数对复合材料显微组织和力学性能的影响规律，深入分析了多向锻造过程中微纳双尺度颗粒对基体组织和力学性能演变的协同机制，成功制备出性能优异的微纳双尺度颗粒增强钛基复合材料，并揭示了其强韧化机理。本研究可为颗粒增强钛基复合材料的设计与制备及工程化应用提供理论支撑。