Fundamental Insights into Multi-element Grain Boundary Segregation in Nanocrystalline Alloys

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NONTECHNICAL SUMMARYThis award supports research and educational activities aimed at gaining fundamental insights into the segregation of multiple elemental species to grain boundaries, and how it affects grain growth in nanocrystalline metallic alloys. Nearly all functional and structural materials are polycrystalline systems; they are composed of differently oriented crystalline grains that are joined at internal interfaces, termed grain boundaries. The grain size and distribution in a metal greatly influences many engineering properties, including mechanical, thermal, and electrical. For example, the mechanical strength of a metal increases rapidly with decreasing grain size. However, due to their small grain size and high density of grain boundaries, nanocrystalline materials are usually structurally unstable. As a result, they undergo rapid grain growth, which limits their use in many technological applications. In this project, the PI will investigate the segregation of multiple types of elemental species to grain boundaries and its role in grain growth in multi-component alloys. The research involves theoretical development and numerical implementation of mathematical models that will be used to simulate the dynamics of grain boundary segregation and grain growth kinetics. A primary focus of this project will be on metallic alloys composed of three different types of elements. Lying at the intersection of materials science and applied mathematics, this project will impact numerous areas of materials physics, chemical thermodynamics, and nanotechnology. Further, this project will provide an avenue to train future-generation of engineers and scientists with the skill set necessary for careers in knowledge-intensive industries in South Carolina, which is an emerging technology and manufacturing hub. The PI will design an “Atomic Legos” outreach activity to engage K-12 students in materials science and help them learn about crystals and metals. This project leverages Clemson’s “Creative Inquiry” program in order to involve undergraduate students, particularly women and underrepresented groups, in scientific research.TECHNICAL SUMMARYThis award supports the development of a mesoscale theoretical and computational modeling framework aimed at advancing our fundamental understanding of the segregation of multiple types of elemental species to grain boundaries and its role in grain growth and thermal stability of nanocrystalline metallic alloys. Owing to their nanoscale grain size, nanocrystalline materials exhibit a unique combination and properties and functionalities. However, rampant grain growth during materials processing or under service conditions is considered one of the main hurdles to the large-scale use of nanocrystalline metals in many engineering technologies. In this project, the PI aims to elucidate key multi-element grain boundary segregation mechanisms that control grain boundary migration and grain growth in metallic alloys. Specific goals of this project include: (1) Development of a theoretical and computational phase field model of multi-element grain boundary segregation in multi-component alloys that accounts for bulk and interface thermodynamics and is able to simulate the microstructural evolution over diffusive scales; (2) Perform theoretical analysis and computational studies to quantify the thermodynamic and kinetic effects of multi-element grain boundary segregation on the thermal stability of nanocrystalline alloys; (3) Quantify the role of the grain boundary network effect in solute partitioning and distribution within grain microstructures. Lying at the intersection of materials science and applied mathematics, this project will impact numerous areas of materials physics, chemical thermodynamics, and nanotechnology. Further, this project will provide an avenue to train future-generation of engineers and scientists with the skill set necessary for careers in knowledge-intensive industries in South Carolina, which is an emerging technology and manufacturing hub. The PI will design an “Atomic Legos” outreach activity to engage K-12 students in materials science and help them learn about crystals and metals. This project leverages Clemson’s “Creative Inquiry” program in order to involve undergraduate students, particularly women and underrepresented groups, in scientific research.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.