Mechano-chemical coupling during precipitate formation in Al-based alloys

铝合金析出物形成过程中的机械-化学耦合

• 批准号: 257547071
• 负责人: Professor Dr. Sergiy Divinski
• 金额: --
• 依托单位: Max-Planck-Institut für Eisenforschung GmbH (MPIE)
• 依托单位国家: 德国
• 项目类别: Priority Programmes
• 财政年份: 2014
• 资助国家: 德国
• 起止时间: 2013-12-31 至 2018-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/257547071?language=en
• 关键词: Mechano; chemical; coupling; during; precipitate

Al-based alloys are important industrial materials in view of a continuously rising demand for high strength and light-weight alloys for structural applications. A combination of ultra-fine grained (UFG) microstructure formation, grain size strengthening and precipitation hardening offers attractive routes to produce semi-finished products with high strength and endurance limit, good ductility and sufficient fracture toughness. In the case of Al-Mg-Sc alloys the formation of an UFG microstructure can significantly affect the structure, chemistry and distribution of second-phase precipitates within the Al matrix. Technical alloys with the additional solutes Zr, Ti, Mg and Mn give rise to additional phenomena like the formation of core-shell nanoparticles. It is therefore the aim of the present project to understand and resolve the coupling between thermo-chemistry and thermo-mechanics underlying these processes.To achieve this goal, ab initio based atomistic simulations, accompanied by dedicated and carefully selected experiments will also be performed in the second period of the project. The investigation of the effect of the stress field caused by the microstructure and external loads on the local chemistry and thermodynamics will be extended to multicomponent systems. Moreover, to simulate precipitate formation under strongly strained conditions a new kinetic Monte-Carlo scheme that allows to include medium and long range elastic interactions will be applied. The coupled thermodynamic-kinetic approach will not only allow a detailed analysis of how large local strain fields affect the formation and chemistry of precipitates, but also the opposite route, i.e. how the formation of a new chemical phase (precipitates) affects the mechanical strain fields. Highlights of the second phase are the formation of core-shell-nanoparticles and the influence of grain boundaries. The development of a reliable method and understanding is not possible without careful comparisons and benchmarks against well-selected and project specific measurements. Compression-shear deformation experiments will provide new insights into the distribution of precipitates. An in-depth analyses of the microstructure and local chemistry in the UFG alloys is obtained by transmission electron microscopy and related methods. In parallel, radio-tracer diffusion experiments under load will provide data on how mechanical deformations affect the chemical composition and diffusion mobilities.The synergy effects of this joined experimental and theoretical approach will allow to systematically explore the mechano-chemical coupling in a technologically relevant materials system and to improve our fundamental understanding of the complex interplay between strain, chemistry, structure, kinetics of interfaces, precipitate formation and their reverse effect on the mechanical response.

鉴于结构应用对高强度和轻质合金的需求不断增长，铝合金是重要的工业材料。超细晶粒 (UFG) 微观结构形成、晶粒尺寸强化和沉淀硬化相结合，为生产具有高强度和耐久性极限、良好延展性和足够断裂韧性的半成品提供了有吸引力的途径。对于 Al-Mg-Sc 合金，UFG 微观结构的形成可以显着影响 Al 基体中第二相沉淀物的结构、化学性质和分布。含有附加溶质 Zr、Ti、Mg 和 Mn 的技术合金会产生附​​加现象，例如形成核壳纳米颗粒。因此，本项目的目标是理解和解决这些过程背后的热化学和热机械之间的耦合。为了实现这一目标，还将进行基于从头算的原子模拟，并辅以专门和精心挑选的实验。项目第二期。由微观结构和外部载荷引起的应力场对局部化学和热力学影响的研究将扩展到多组分系统。此外，为了模拟强应变条件下沉淀物的形成，将应用一种新的动力学蒙特卡罗方案，该方案允许包括中程和长程弹性相互作用。热力学-动力学耦合方法不仅可以详细分析局部应变场有多大影响沉淀物的形成和化学性质，还可以进行相反的分析，即新化学相（沉淀物）的形成如何影响机械应变场。第二阶段的亮点是核-壳-纳米粒子的形成和晶界的影响。如果没有针对精心挑选的项目特定测量进行仔细比较和基准测试，就不可能开发出可靠的方法和理解。压剪变形实验将为沉淀物的分布提供新的见解。通过透射电子显微镜和相关方法对 UFG 合金的微观结构和局部化学进行了深入分析。同时，负载下的放射性示踪剂扩散实验将提供有关机械变形如何影响化学成分和扩散迁移率的数据。这种实验和理论方法相结合的协同效应将允许系统地探索技术相关材料中的机械-化学耦合系统并提高我们对应变、化学、结构、界面动力学、沉淀物形成及其对机械响应的反向影响之间复杂相互作用的基本理解。