Tailored precipitation (B2, L21) strengthened, compositionally complex FeAlCr (Mn, Co, Ni, Ti) alloys for high temperature applications

适用于高温应用的定制沉淀 (B2、L21) 强化、成分复杂的 FeAlCr（Mn、Co、Ni、Ti）合金

• 批准号: 388541188
• 负责人: Professor Dr. Christian Liebscher
• 金额: --
• 依托单位: Lehrstuhl für Werkstoffchemie (MCh)
• 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 2020-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/388541188?language=en
• 关键词: Tailored; precipitation; B2; L21; strengthened

High entropy alloys (HEAs) or compositionally complex alloys (CCAs) are multicomponent systems with typically more than five alloying elements. The large compositional space offers attractive alloy design strategies and initially it was assumed that by maximizing the entropy of mixing, true single phase solid solutions can be established. However, only very few successful single phase alloys could be obtained in the past 10 years of HEA development and in the majority of cases multi-phase microstructures, including intermetallic phases, form. However, such multi-phase alloy systems could yield alloys bridging the enormous gap between Titanium and Nickel-based alloys in terms of alloy density and application temperature, but this application field is rarely explored.The aim of the present work is to develop body-centered cubic (BCC) CCAs with tailored precipitates based on B2- and/or L21-phases with densities of < 7 g/cm3 for high temperature applications up to 900ºC. In a first step, the phase formation in the rather unexplored composition space of FeAlCr (Mn, Co, Ni, Ti) is explored by high throughput screening and characterization based on thin film deposition techniques. Promising alloy candidates are identified fulfilling the conditions to have a BCC crystal structure and showing either B2, L21 or both types of precipitate phases. In further steps, these alloy candidates are then obtained by conventional casting techniques to investigate the microstructure and precipitate structure in as-cast alloys and to evaluate their high temperature stability after thermal exposure of up to 900ºC. The alloy design approach is based on a microstructural optimization in terms of precipitate morphology, coherency with the supersaturated BCC matrix and their volume fraction. Tailored microstructures are then mechanically tested from room up to temperatures of 900ºC to establish the microstructure-property relationship for further optimization steps. In addition, first high temperature creep experiments give insights into the microstructural stability at elevated temperatures under load and the operating deformation mechanisms.The microstructural characterization and mechanical property evaluation throughout the alloy design process are cornerstones of the presented research. The combination of mechanical testing with advanced characterization techniques such as X-ray diffraction, transmission electron microscopy and atom probe tomography is guiding the development of these novel alloy systems from a mesoscopic length scale down to the atomic scale.

高熵合金（HEAs）或成分复杂合金（CCAs）是由五种以上合金元素组成的多组分系统。大的成分空间提供了有吸引力的合金设计策略，最初假设通过最大化混合熵，可以建立真正的单相固溶体。然而，在过去10年的HEA发展中，只有极少数成功的单相合金，在大多数情况下，形成了包括金属间相在内的多相显微组织。然而，这种多相合金体系可以在合金密度和应用温度方面弥补钛基和镍基合金之间的巨大差距，但这一应用领域很少被探索。目前工作的目的是开发具有基于B2和/或l21相的定制沉淀的体心立方（BCC） cca，密度< 7 g/cm3，可用于高达900ºC的高温应用。在第一步中，通过基于薄膜沉积技术的高通量筛选和表征，探索了FeAlCr （Mn, Co, Ni, Ti）在相当未开发的成分空间中的相形成。有希望的候选合金被确定满足条件，具有BCC晶体结构，并显示B2， L21或两种沉淀相。在进一步的步骤中，这些候选合金然后通过常规铸造技术获得，以研究铸态合金的显微组织和沉淀结构，并评估其在高达900℃的热暴露后的高温稳定性。合金的设计方法是基于微观结构的优化，包括沉淀形态、与过饱和BCC基体的一致性以及它们的体积分数。然后在室温至900℃的温度下对定制的微结构进行机械测试，以建立微结构-性能关系，以便进一步优化步骤。此外，首次进行了高温蠕变实验，深入了解了高温载荷下的微观组织稳定性和运行变形机制。合金设计过程中的微观组织表征和力学性能评估是本研究的基础。机械测试与先进的表征技术（如x射线衍射、透射电子显微镜和原子探针断层扫描）的结合，正在指导这些新型合金系统从介观长度尺度到原子尺度的发展。