Materials World Network: Developing a New Mg Alloy with Optimized Texture for Enhanced Formability

材料世界网络：开发一种具有优化织构以增强成型性的新型镁合金

• 批准号: 0603066
• 负责人: Sean Agnew
• 金额: $ 27万
• 依托单位: University of Virginia Main Campus
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2006
• 资助国家: 美国
• 起止时间: 2006-07-01 至 2010-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0603066&HistoricalAwards=false
• 关键词: Materials; World; Network; Developing; New

The goal of this project, a joint effort between the University of Virginia (UVA) and the Technical University Hamburg Harburg (TUHH) and the nearby national laboratory GKSS at Geestacht, Germany, is to develop a new wrought Mg alloy with optimized texture for promoting enhanced formability. Despite many attractive properties, the application of Mg alloy sheet is limited, in part, due to poor low temperature formability. Their forming behavior is strongly affected by crystallographic texture because of the intrinsic plastic anisotropy of the hexagonal close packed crystal structure. Conventional Mg alloy sheets exhibit strong textures (with basal planes parallel to the sheet plane) with little variation between alloys. It has only recently been reported that alloys containing significant additions of rare earth (RE) elements and yttrium (Y) develop much weaker textures during extrusion than conventional alloys, and preliminary results show that randomizing the texture of Mg alloy sheets results in improved formability. The mechanism by which RE/Y additions impart a change in the texture evolution is presently unknown, thus, an appropriate alloy design strategy is also unknown. It has been suggested that particle stimulated nucleation (PSN) of recrystallization (either static or dynamic) is responsible. However, unpublished results show that texture modification is also possible in dilute RE/Y alloys which are expected to have very little second phase. A critical step in the proposed research will be to discriminate between solid solution alloying effects and particle related effects. Computer modeling will be used to focus both the search for i) controlling mechanisms and ii) optimal compositions once the mechanism(s) of texture modification are identified. For example, it is possible that RE/Y solute atoms form nano-scale clusters which interact with dislocations in ways not presently accounted for by theories which assume ideal, random solutions. If the modeling results suggest as much, validation will be sought using diffuse scattering at a synchrotron or other experimental techniques. Regardless, phase stability and calculated phase diagram (CALPHAD) analyses will be used to identify promising compositions. Additionally, there is little experience upon which to recommend optimal textures. Forming limit diagrams (FLDs) provide an assessment of sheet metal response under various forming conditions. The texture dependence of the FLD will be predicted using a polycrystal plasticity model. This approach allows exploration of concepts which are not possible experimentally (e.g., to alter texture independent of grain size, alloy content, etc.) The predictions will be validated using experimental FLDs from TUHH/GKSS. Students and young scientists will travel to the partner institutions to become involved in relevant aspects of the research, for instance students developing formability models at UVA will benefit strongly from exposure to formability testing facilities and expertise at TUHH/GKSS. The proposed research will serve a broader goal of enabling increased application of lightweight Mg alloys in automobiles, thereby promoting improved fuel efficiency and reduced emissions of harmful greenhouse gases. Further, there are a range of portable electronics goods (cell phones, cameras, laptops, etc.) which would benefit from a readily manufactured material with a density which is typical of polymeric materials and the durability, thermal conductivity and electronic interference shielding typical of a metal. The fundamental concepts explored and models developed, e.g., recrystallization, atomic clustering, and texture effects, have broad implications for many materials systems.

该项目由弗吉尼亚大学(UVA)和汉堡哈堡工业大学(TUHH)以及附近位于德国Geestacht的国家实验室GKSS共同努力，目的是开发一种具有优化织构的新型变形镁合金，以提高成形性。尽管镁合金板材具有许多诱人的性能，但由于低温成形性差，其应用受到了限制。由于六方密排晶体结构的本征塑性各向异性，它们的形成行为受到晶体织构的强烈影响。传统的镁合金板材具有很强的织构(基面平行于板材平面)，不同合金之间几乎没有变化。最近才有报道称，大量添加稀土(RE)和Y(Y)的合金在挤压过程中产生的织构比传统合金弱得多，初步结果表明，将镁合金板材的织构随机化可以改善成形性能。RE/Y掺杂改变织构演化的机制目前尚不清楚，因此，合适的合金设计策略也是未知的。研究表明，再结晶(静态或动态)的颗粒激发形核(PSN)起主要作用。然而，未发表的结果表明，稀薄RE/Y合金的织构改变也是可能的，因为稀薄RE/Y合金的第二相很少。拟议研究中的一个关键步骤将是区分固溶体合金化效应和颗粒相关效应。一旦确定了织构修饰的机理(S)，将使用计算机模拟来集中寻找i)控制机理和ii)最佳成分。例如，RE/Y溶质原子可能形成纳米尺度的团簇，这些团簇与位错相互作用的方式目前没有被假设理想的随机解决方案的理论所解释。如果模拟结果表明了这一点，将使用同步加速器的漫射散射或其他实验技术进行验证。无论如何，将使用相稳定性和计算相图(CALPHAD)分析来确定有希望的成分。此外，几乎没有经验来推荐最佳纹理。成形极限图(FLD)提供了在不同成形条件下的板料响应的评估。FLD的织构依赖关系将使用多晶塑性模型进行预测。这种方法允许探索实验上不可能的概念(例如，独立于晶粒度、合金含量等改变织构)。这些预测将使用TUHH/GKSS的实验FLDS进行验证。学生和青年科学家将前往合作机构，参与研究的相关方面，例如，在弗吉尼亚大学开发成形性模型的学生将从接触TUHH/GKSS的成形性测试设施和专业知识中受益匪浅。拟议的研究将服务于一个更广泛的目标，即使更多的轻质镁合金能够在汽车上得到应用，从而促进提高燃料效率和减少有害温室气体的排放。此外，还有一系列便携式电子产品(手机、相机、笔记本电脑等)。这将受益于易于制造的材料，其具有典型的聚合物材料的密度和典型的金属的耐久性、导热性和电子干扰屏蔽。探索的基本概念和发展的模型，例如再结晶、原子聚集和织构效应，对许多材料系统具有广泛的意义。