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Molecular dynamics simulations to identify atomistic deformationmechanisms in two-phase lamellar TiAl alloys

分子动力学模拟识别两相层状 TiAl 合金的原子变形机制

基本信息

批准号：
404541620
负责人：
Privatdozentin Dr. Rebecca Janisch
金额：
--
依托单位：
Abteilung Mikromechanische und makroskopische Modellierung
依托单位国家：
德国
项目类别：
Research Grants
财政年份：
2018
资助国家：
德国
起止时间：
2017-12-31 至 2021-12-31
项目状态：
已结题

来源：
https://gepris.dfg.de/gepris/projekt/404541620?language=en
关键词：
Molecular dynamics simulations identify atomistic

项目摘要

Modern structural materials usually display a hierarchical microstructure, and hence interdependent deformation mechanisms on different length-scales, which determine the macroscopic behaviour. Using computational material models with representative volume elements or suitable homogenisation methods, we can identify the relevant microstructural parameters that dominate this deformation behaviour. However, very often the understanding of defect-microstructure interactions on the smallest length scale is missing. This understanding is crucial for a purposeful improvement of continuum models and a systematic optimisation of the microstructure. Of highest importance in this context is to determine the significance of different processes such as dislocation motion and twinning and the conditions under which they occur. These conditions can be varied systematically within atomistic simulations, and the resulting processes can be analysed.In the project at hand deformation and fracture of lamellar microstructures in two-phase TiAl alloys is investigated using molecular dynamics simulations. The ratio ofstrength and deformability of TiAl alloys can be optimized by creating lamellar microstructures. They are characterised by additional microstructural parameters besides the grain size, such as the spacing of alpha-2 lamellae within the grains, the thickness of the gamma-lamellae between the alpha-2 lamellae, and the sequence and frequency of certain gamma-gamma interfaces (pseudo-twin, rotational boundary, true twin). All these parameters contribute to the confinement of dislocation motion, respectively twin formation, in a manner which is still unresolved. Experimentally, a Hall-Petch-type strengthening behaviour is observed. In this project its range of validity and the way in which the individual microstructural parameters contribute to it, will be clarified. The questions, which length- scale in a multiphase, nano-structured alloy dominates the strength and toughness, and which critical values control twin formation and dislocation motion, are of general importance for formulating quantitative multiscale models of deformation and fracture in hierarchical microstructures.

现代结构材料通常表现出分层的微观结构，因此在不同的长度尺度上具有相互依赖的变形机制，这决定了宏观行为。使用具有代表性的体积元素或合适的均匀化方法的计算材料模型，我们可以确定主导这种变形行为的相关微观结构参数。然而，往往缺乏对最小长度尺度上的缺陷-微观结构相互作用的理解。这种理解对于有目的地改进连续模型和系统地优化微观结构至关重要。在这方面，最重要的是确定不同过程的意义，如位错运动和孪生，以及它们发生的条件。这些条件可以在原子模拟中系统地改变，并且可以分析由此产生的过程。在手头的项目中，使用分子动力学模拟研究了两相TiAl合金中层状微观结构的变形和断裂。TiAl合金的强度和变形能力的比例可以通过创建片层组织来优化。它们的特征在于除了晶粒尺寸之外的其他微观结构参数，例如晶粒内α-2层的间距，α-2层之间的γ-层的厚度，以及某些γ-γ界面（假孪晶，旋转边界，真孪晶）的顺序和频率。所有这些参数有助于限制位错运动，分别孪晶的形成，在某种程度上，这仍然是悬而未决的。在实验上，观察到一个霍尔-佩奇型强化行为。在这个项目中，其有效性的范围和方式，其中个人的微观结构参数有助于它，将得到澄清。多相纳米结构合金的长度尺度决定强度和韧性，孪晶的形成和位错的运动由哪个临界值控制，这些问题对于建立分级显微组织中变形和断裂的定量多尺度模型具有普遍的重要性。