DMREF/Collaborative Research: Low Cost, High Strength and Ductile Mg Alloys

作为所有结构金属中最轻的一种，镁合金在许多重量对性能和效率至关重要的应用中具有巨大的潜力，包括汽车、铁路和航空航天工业。然而，由于加工成本较高，变形镁合金的利用率仍然很低。设计材料革新和设计我们的未来(DMREF)奖支持基础研究，这些研究可以通过对加工、材料的微米级结构和性能之间的关系的基本了解，实现高强度、高延性的镁合金的高效加工。这个项目将教育不同的学生和博士后研究员，为他们提供在由计算和实验研究人员组成的跨学科团队中发挥作用所需的技能，因为他们开展了对美国制造、运输和国防部门有益的工作。在这项工作中，研究人员将研究在降水的早期阶段形成的纳米级溶质团簇，即众所周知的吉尼斯-普雷斯顿(GP)区，以了解它们如何对材料性质做出贡献，特别是最近观察到的应变率敏感性的增加。超越过渡态理论的新计算方法将被用来评估位错-GP区相互作用的动力学。实验评估将使用应变速率跳跃和重复应力松弛测试以及晶体塑性建模相结合的方法进行。在这项工作中建立的结构-性能关系将用于指导涉及GP区的合金设计策略。该项目还旨在利用基于第一性原理的计算方法来预测镁合金中GP区的原子结构和热力学性质。为了验证和指导这些模拟工作，使用了透射电子显微镜和电子能量损失谱方法来探测GP区的原子和电子尺度结构。这些联合努力将弥合关于溶质混合、相形成和界面的自由能与导致GP区形成和形态的相干应变之间相互作用的知识鸿沟。该奖项反映了NSF的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。

As the lightest of all structural metals, magnesium (Mg) alloys have great potential to be used in many applications where weight is critical to performance and efficiency, including the automotive, rail and aerospace industries. Yet wrought Mg alloys remain underutilized, due to a high processing cost. This Designing Materials to Revolutionize and Engineer our Future (DMREF) award supports fundamental research which could lead to efficient processing of high strength, high ductility Mg alloys through fundamental understanding of the relationships among processing, the micrometer-scale structure of the material, and performance. This project will educate a diverse group of students and postdoctoral fellows, providing them with the skills required to function within interdisciplinary teams comprised of computational and experimental researchers, as they perform work of benefit to the US manufacturing, transportation, and defense sectors.In this work, the researchers will investigate nanoscale solute clusters which form in the early stage of precipitation, known as Guinier-Preston (GP) zones, to understand how they contribute to materials properties, in particular to a recently observed increase in strain rate sensitivity. New computational methods that extend beyond transition state theory will be used to assess the kinetics of dislocation-GP zone interactions. Experimental assessments will be made using a combination of strain rate jump and repeated stress relaxation testing together with crystal plasticity modeling. The structure-property relationships established in this work will be used to guide alloy design strategies involving GP zones. This project also aims to predict the atomic structures and thermodynamic properties of GP zones in Mg alloys using first-principles-based computational approaches. To validate and guide these modeling efforts, transmission electron microscopy (TEM) and electron energy loss spectroscopy (EELS) approaches are employed to probe the atomistic- and electronic-scale structure of the GP zones. These combined efforts will close the knowledge gap pertaining to the interplay between the free energies of solute mixing, phase formation and interfaces, and the coherency strains which are responsible for the formation and morphology of GP zones.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.