Experimental Characterization of Deformation Mechanisms in Magnesium Rare Earth Alloys

非技术摘要：现代载人和自动驾驶车辆的总体通用性、可部署性和能效与它们的重量成反比。镁的重量几乎是钢的四倍，其超低密度和高比强度使镁合金成为商业和国防平台的轻质材料。然而，镁的塑性和成形性有限，这是因为它的六方晶体结构导致了强烈的塑性各向异性，这限制了它的使用。最近通过稀土合金化在成形性方面取得了进展，本项目将详细了解这些稀土元素对控制延展性和成形性的原子尺度机制的影响。从这项实验研究中获得的见解将加速合金的开发，并有助于在各种汽车、军事和航空航天应用中促进具有成本效益的轻量化。合作将提供有意义的STEM教育和职业发展机会，参加SABES将为JHU研究人员提供一个亲自与巴尔的摩小学生互动的机会，并让他们对STEM活动有一个独特的看法。技术摘要：这项研究的科学价值在于我们希望看到和了解支撑镁合金力学响应的变形机制，并阐明稀土元素在提高延展性和改善成形性方面的基础作用。将进行的实验任务包括：(1)确定镁稀土合金中的活动滑移系；(2)位错形态和微观结构的细观表征；(3)位错核的原子尺度表征；(4)影响孪晶形核和生长的因素的确定。将使用基于扫描电子显微镜的EBSD成像和STEM观测，以及基于透射电子显微镜的明场、弱束暗场、高分辨EM和STEM成像以及纳米尺度的定向和弹性应变映射。收集的实验数据将被数字存档，并用于促进材料基因组倡议设想的综合计算材料科学和工程(ICMSE)。

Nontechnical abstract: The overall versatility, deployability and energy efficiency of modern manned and autonomous vehicles are inversely related to their weight. Magnesium (Mg) is nearly four times lighter than steel and its ultra-low density and high specific strength make Mg alloys attractive lightweighting materials for commercial and defense platforms. However, the use of Mg has been inhibited by its limited ductility and formability, which is attributed to strong plastic anisotropy that results from its hexagonal crystal structure. Recent gains in formability have been achieved through rare earth alloying, and this project will provide a detailed understanding of the influence that these rare earth elements have on the atomic-scale mechanisms that govern ductility and formability. The insights obtained from this experimental study will accelerate alloy development and help promote cost-effective lightweighting in a wide variety of automotive, military and aerospace applications. Collaborations will provide meaningful STEM educational and career advancement opportunities, and participation in SABES will offer JHU researchers a chance to personally interact with and give Baltimore elementary school students a unique perspective on STEM activities. Technical Abstract:The scientific merit of this study is predicated in our desire to see and understand the deformation mechanisms that underpin the mechanical response of Mg alloys and to elucidate the fundamental role that rare earth elements have in increasing ductility and improving formability. The experimental tasks to be undertaken include: (i) identification of active slip systems in Mg-RE alloys, (ii) meso-scale characterization of dislocation morphologies and microstructures, (iii) atomic-scale characterization of dislocation cores, and (iv) identification of the factors influencing twin nucleation and growth. SEM-based EBSD mapping and STEM observations and TEM-based bright field, weak-beam dark field, HREM, and STEM imaging and nanoscale orientation and elastic strain mapping will be employed. The experimental data collected will be digitally archived and used to promote Integrated Computational Materials Science and Engineering (ICMSE) as envisaged by the Materials Genome Initiative (MGI).