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Grain boundary segregation in magnesium alloys and its role in controlling the microstructure and mechanical properties

镁合金中的晶界偏析及其对显微组织和力学性能的控制作用

基本信息

批准号：
394480829
负责人：
Dr.-Ing. Talal Al-Samman
金额：
--
依托单位：
Institut für Metallkunde und Metallphysik (IMM)
依托单位国家：
德国
项目类别：
Research Grants
财政年份：
2017
资助国家：
德国
起止时间：
2016-12-31 至 2021-12-31
项目状态：
已结题

来源：
https://gepris.dfg.de/gepris/projekt/394480829?language=en
关键词：
Grain boundary segregation magnesium alloys

项目摘要

Magnesium-zinc alloys containing rare earth (RE) additions exhibit enhanced cold formability owing mostly to commercially attractive weak textures developed upon recrystallization. However, it is still unclear whether the texture modification effect in these alloy systems arises primarily from single alloying elements or from their combination. Due to the complex interplay of Zn and RE the exact underlying mechanisms remain an outstanding issue. It is hypothesized that suppression of dynamic recrystallization during deformation and retardation of grain boundary motion during static recrystallization due to solute segregation effects play a key role in understanding the rare earth effect on texture. Based on a selection criterion combining large atomic size misfit with magnesium and high bulk solubility, the proposed project aims to investigate the GB segregation characteristics of several potential RE (Gd, Dy and Er) and non-RE elements, such as Ca that has a large atomic size equivalent to RE metals, and is thus expected to show the RE texture change effect. The fact that RE elements are relatively expensive and not readily available across the globe renders the investigation of Ca as a substitute for RE technologically attractive. Special attention will be given to resulting solute drag effects on altering common recrystallization and growth mechanisms requiring boundary migration, and how this affects the development of texture and microstructure during annealing. Beside the effect of single alloying elements in binary alloys, synergy effects and effects of varying the concentration ratios of RE and Zn in ternary alloys will be investigated. The work program will utilize powerful structural and chemical characterization techniques, such as 3D atom probe tomography, as well as advanced level-set modeling of anisotropic grain growth to understand the process of selective grain growth and its effect on texture formation. It is highly anticipated that the research findings of the project will lead to sound physical basis for a new alloy design concept exploiting GB segregation for tailoring the microstructure of Mg alloys during thermomechanical processing to obtain a unique combination of improved strength and ductility.

添加稀土(RE)的镁锌合金具有更好的冷成形性能，这主要是由于在再结晶过程中形成了具有商业吸引力的弱织构。然而，目前还不清楚这些合金系统中的织构变质效应主要是来自单一的合金元素还是它们的组合。由于锌和稀土的复杂相互作用，确切的潜在机制仍然是一个悬而未决的问题。认为由于溶质偏析效应对变形过程中动态再结晶的抑制和静态再结晶过程中晶界运动的延缓是理解稀土对织构影响的关键。基于大原子尺寸失配与镁和高体溶度相结合的选择标准，该项目旨在研究几种潜在的RE(Gd，Dy和Er)和非稀土元素的GB偏析特征，例如具有相当于稀土金属的大原子尺寸的Ca，从而有望显示出RE织构变化效应。稀土元素相对昂贵且不容易在全球范围内获得的事实，使作为稀土替代品的钙的研究在技术上具有吸引力。将特别关注在改变常见的再结晶和需要边界迁移的生长机制方面所产生的溶质阻力效应，以及这如何影响退火过程中织构和微结构的发展。除了单一合金元素在二元合金中的作用外，还将研究稀土和锌在三元合金中的协同效应和不同浓度比的影响。该工作计划将利用强大的结构和化学表征技术，如3D原子探针层析成像，以及各向异性颗粒生长的高级水平集建模，以了解选择性颗粒生长过程及其对织构形成的影响。人们高度期待该项目的研究成果将为一种新的合金设计概念奠定坚实的物理基础，该概念利用GB偏析来定制镁合金在热机械加工过程中的微观结构，以获得改善的强度和延展性的独特组合。