Identification of the intrinsic deformation mechanisms of single phase body-centered cubic high entropy alloys

单相体心立方高熵合金本征变形机制的识别

• 批准号: 388672790
• 负责人: Dr. Patric Alfons Gruber
• 金额: --
• 依托单位: Department of Mechanical Engineering
• 依托单位国家: 德国
• 项目类别: Priority Programmes
• 财政年份: 2017
• 资助国家: 德国
• 起止时间: 2016-12-31 至 2022-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/388672790?language=en
• 关键词: Identification; intrinsic; deformation; mechanisms; single

Body-centered cubic (BCC) refractory high-entropy alloys (HEAs) have been studied as novel metallic systems for high-temperature applications due to their, for example, superior strength, excellent thermal stability, and oxidation resistance even at elevated temperatures. To date, the research emphasis in the field of refractory HEAs has been upon the development and evaluation of the resulting microstructure. However, the intrinsic deformation mechanisms of the single-phase BCC HEAs are still under debate. For example, a mean field solute-strengthening model severely underestimates the critical stresses for dislocation motion in single phase BCC HEAs, whereas the later solute-strengthening model is consistent with experimental yield strengths of face-centered cubic single phase HEAs. In general, the mechanical behavior of BCC HEAs depend on intrinsic properties, such as the chemical composition, microstructures, and the interaction of defects with the different microstructural components, as well as extrinsic parameters, such as temperature, and strain rate. The proposed project aims at determining the intrinsic deformation mechanisms of single-phase BCC HEAs and at characterizing the chemical/microstructural stability under deformation with the goal to predict their structural integrity at room-temperature and in the transition to the high-temperature regime at 700K. The deformation kinetics and dislocation slip systems are determined and linked to the characteristic deformation signatures of the macroscopically ductile Ta-Nb-Hf-Zr-Ti HEA and the macroscopically apparently brittle Nb-Mo-Cr-Ti-Al HEA in the proposed synergistic approach, which combines atomistic simulation methods and advanced temperature-dependent nano and micromechanical experiments. The mechanical tests are supplemented by multiscale and extended spatially-resolved microstructural and chemical analysis. Electronic structure calculations simulate explicitly disordered HEAs using special quasi-random structure and provide a chemical accurate prediction of the intrinsic fluctuations of materials parameter, e.g., ideal shear strength and generalized stacking fault energies. The possible slip systems and the associated screw/edge dislocation anisotropies are determined on the basis of simulation-informed dislocation theory. A kinetic Monte Carlo method is developed to elucidate element-specific segregation trends during deformation. The combined simulations-and-experiment ansatz will allow to formulate a verifiable phenomenological model for the deformation processes in single-phase BCC HEAs at room-temperature.

体心立方（BCC）耐火高熵合金（HEAs）由于其例如上级的强度、优异的热稳定性和即使在升高的温度下的抗氧化性而被研究为用于高温应用的新型金属系统。到目前为止，耐火HEAs领域的研究重点一直是对所得微观结构的开发和评估。然而，单相体心立方HEAs的内在变形机制仍然存在争议。例如，平均场溶质强化模型严重低估了单相BCC HEAs中位错运动的临界应力，而后者溶质强化模型与面心立方单相HEAs的实验屈服强度一致。一般来说，BCC HEAs的机械行为取决于固有性质，例如化学组成、微结构和缺陷与不同微结构组分的相互作用，以及外部参数，例如温度和应变速率。该项目旨在确定单相BCC HEAs的内在变形机制，并表征变形下的化学/微观结构稳定性，目标是预测其在室温下的结构完整性以及在700 K下向高温制度的过渡。的变形动力学和位错滑移系统的确定和链接到宏观韧性Ta-Nb-Hf-Zr-Ti HEA和宏观上明显脆性Nb-Mo-Cr-Ti-Al HEA的特征变形签名在建议的协同方法，它结合了原子模拟方法和先进的温度依赖性纳米和微观力学实验。机械测试的补充多尺度和扩展的空间分辨微观结构和化学分析。电子结构计算使用特殊的准随机结构来模拟显式无序的HEAs，并提供材料参数的内在波动的化学准确预测，例如，理想剪切强度和广义层错能。可能的滑移系和相关的螺旋/刃位错各向异性的基础上，模拟通知位错理论确定。动态蒙特卡罗方法的发展，以阐明特定元素的偏析趋势在变形过程中。结合模拟和实验分析，将允许制定一个可验证的现象学模型在室温下单相BCC HEAs的变形过程。