超细晶难熔高熵合金强韧化与变形的位错机制研究

Refractory high-entropy alloys is a new kind of high temperature structural materials. Investigation of deformation mechanism, strengthening and toughening mechanism of refractory high entropy alloy can not only enrich the theoretical system of deformation, but also provide a scientific basis for the preparation of high entropy alloys with high strength and toughness and the theoretical basis for material processing and study of follow-up service performance. Using the theoretical analysis and the experimental testing, this project will establish model to study the interaction of microstructures, such as dislocations, disclination, precipitates, nanoscale grain boundaries and voids, under condition of severe lattice distortion, in nanoscale rare earth oxide dispersion strengthened ultra-fine grain / nanocrystalline light-weight refractory high entropy alloy. The effect of severe lattice distortion effect, nano scale dispersion phase and nanocrystalline on mechanism of strengthening and toughening, deformation and fracture behavior in the refractory high entropy alloy will be revealed. The main factors and control conditions to determine the strengthening and toughening mechanism and fracture failure of refractory high entropy alloy will be obtained. An analytical model was established to predict the quantitative relationship between the parameters of microstructures and strength as well as fracture toughness of ultrafine grained and nanocrystalline refractory high entropy alloys. The optimization of the design parameters and processing parameters of the refractory high entropy alloy will be discussed in the project.

难熔高熵合金是一类新型的高温结构材料，研究难熔高熵合金变形机制和强韧化机理不但可以丰富和发展合金变形的理论体系，而且为设计制备高强韧新型高熵合金提供科学依据，为材料加工和后续服役性能研究提供基础理论。本项目拟以纳米尺度稀土氧化物弥散强化超细晶/纳米晶轻质难熔高熵合金为研究对象，采用理论分析、数值模拟与实验测试有机结合的方法，研究高熵合金严重晶格畸变条件下位错、向错、纳米尺度弥散相、空隙、晶界等微结构交互作用规律，揭示难熔高熵合金中严重晶格畸变效应、纳米弥散相、纳米晶对高熵合金强韧化、变形和断裂行为的影响机制，获得影响难熔高熵合金强韧化和断裂破坏的主要因素及控制条件。建立预测超细晶/纳米晶高熵合金弥散相等微结构参数与强度、断裂韧性定量关联的解析模型，探讨高熵合金微结构设计参数和制备工艺参数的优化。

基于现代工业发展对新型合金材料的迫切需求，难熔高熵合金作为一类新型的高温结构材料被逐渐开发。然而因其微观结构与力学性能之间的关系还未被完全揭示，而限制了其进一步的应用。本项目充分结合实验、理论分析、分子动力学模拟、位错动力学模拟和机器学习方法，研究了纳米尺度稀土氧化物弥散强化超细晶/纳米晶轻质难熔高熵合金严重晶格畸变条件下位错、纳米尺度弥散相、空隙、纳米孪晶、晶界等微观结构相互作用机理；基于固溶强化、位错强化、析出强化、晶界强化和孪晶界强化等理论定量计算了高熵合金优异的强度；揭示了轻质难熔高熵合金的强化机制及其贡献比例。根据微观结构演变分析了其塑性变形机理；建立了纳米尺度稀土氧化物弥散强化超细晶/纳米晶轻质难熔高熵合金微观结构参数与断裂韧性的定量关联和解析预测模型。这些难熔高熵合金变形机制和强韧化机理研究结果不但可以丰富和发展合金变形的理论体系，而且为设计制备高强韧新型高熵合金提供科学依据，为材料加工和后续服役性能研究提供基础理论。