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（Mg）合金在许多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，由于加工成本高，锻造镁合金仍然未得到充分利用。该设计材料革命和工程我们的未来（DMREF）奖支持基础研究，通过对加工，材料的微米级结构和性能之间的关系的基本理解，可以导致高强度，高韧性镁合金的有效加工。该项目将培养一批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，因为他们从事的工作对美国的制造业，运输业和国防部门都有好处。在这项工作中，研究人员将研究沉淀早期形成的纳米级溶质团簇，称为Guinier-Preston（GP）区，以了解它们如何影响材料性能，特别是最近观察到的应变率敏感性增加。新的计算方法，超越过渡态理论将被用来评估位错GP区相互作用的动力学。实验评估将使用应变率跳跃和重复应力松弛测试与晶体塑性建模相结合。在这项工作中建立的结构-性能关系将用于指导合金设计策略，涉及GP区。本项目还旨在使用基于第一性原理的计算方法预测镁合金GP区的原子结构和热力学性质。为了验证和指导这些建模工作，透射电子显微镜（TEM）和电子能量损失谱（EELS）的方法来探测GP区的原子和电子尺度的结构。这些共同的努力将缩小有关溶质混合的自由能之间的相互作用的知识差距，相形成和接口，并负责形成和形态的GP区域的相干应变。这个奖项反映了NSF的法定使命，并已被认为是值得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的支持。

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.