Experimental Characterization of Deformation Mechanisms in Magnesium Rare Earth Alloys

非技术性摘要：现代载人和自动驾驶车辆的整体多功能性、可部署性和能源效率与其重量成反比。 镁（Mg）比钢轻近四倍，其超低密度和高比强度使镁合金成为商业和国防平台的有吸引力的轻量化材料。然而，镁的使用受到其有限的延展性和可成形性的限制，这归因于其六方晶体结构导致的强塑性各向异性。 通过稀土合金化，最近在可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可成形性的原子级机制的影响。 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干教育和职业发展的机会，并在SABES参与将提供JHU研究人员有机会亲自互动，并给巴尔的摩小学生干活动的独特视角。 技术摘要：这项研究的科学价值是在我们希望看到和理解的变形机制，支撑镁合金的机械响应，并阐明稀土元素在增加延展性和改善可成形性的基本作用。要进行的实验任务包括：（i）在Mg-RE合金中的活动滑移系统的识别，（ii）位错形态和微观结构的介观尺度表征，（iii）位错核心的原子尺度表征，以及（iv）识别影响孪晶成核和生长的因素。 将采用基于SEM的EBSD映射和STEM观察以及基于TEM的明场、弱束暗场、HREM和STEM成像以及纳米级取向和弹性应变映射。收集的实验数据将被数字化存档，并用于促进材料基因组计划（MGI）所设想的综合计算材料科学与工程（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).