ABSTRACT

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.

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