CAREER: Understanding Energy Statistics and Glide Mechanisms of Dislocations in Concentrated Solid-Solution Alloys

NON-TECHNICAL SUMMARY

Dislocation, a type of crystalline defect caused by the linear misalignment of atoms, plays a crucial role in determining the mechanical properties of metallic materials during processing and service. This Faculty Early Career Development (CAREER) award supports a research and education project aimed at understanding how dislocations move and how their motion affects the deformation behavior of a class of materials known as concentrated solid-solution alloys (CSAs).

In CSAs, different atomic species are randomly mixed in high concentrations, creating locally varied chemical compositions throughout the crystal lattice and spatially fluctuated energy barriers to dislocation motion. These unique atomic-scale features cause dislocations in CSAs to behave differently from those in traditional alloys, leading to mechanical characteristics that are not yet fully understood.

This research project integrates statistical theories, computational modeling, and experimental validation to develop a framework for quantitative predictions of dislocation motion in CSAs. By focusing on CSAs made from multiple refractory metals like niobium, molybdenum and tungsten, the project aims to reveal how local chemical fluctuations influence dislocation motion and how these mechanisms shape the strength and plasticity of CSAs.

The knowledge being generated could lead to new design strategies for novel refractory alloys with superior mechanical properties and room-temperature processability, addressing critical material needs in industries essential to energy and national security, including nuclear energy, electric power generation, and hypersonic aviation and aerospace.

This project also emphasizes education and outreach to engage students of all ages in materials science and engineering (MSE). It offers hands-on, specifically tailored research training for college students of different grades, introduces high school students to engaging topics in materials science, and incorporates artificial intelligence knowledge into the MSE classroom, with the overarching goal of preparing the next generation of scientists and engineers with the necessary knowledge and skills for developing stronger, more durable materials for future technologies.

TECHNICAL SUMMARY

This CAREER award supports an integrated research and education project to understand dislocation glide behavior and its effect on plastic deformation in concentrated solid-solution alloys (CSAs). In these alloys, non-dilute atomic mixing introduces inherent fluctuations in local lattice chemistry, making the energy barriers to dislocation glide (i.e., Peierls barrier) vary randomly from one lattice location to another.

Consequently, dislocations in CSAs behave distinctively from those in traditional dilute alloys, resulting in intriguing strength and plastic properties that remain poorly understood. By integrating statistical theories, multiscale dislocation modeling, and experimental validation, this project is developing a probabilistic framework for describing Peierls barrier variations and dislocation glide dynamics in CSAs.

Using body-centered cubic (bcc) CSAs of refractory metal elements as a model system, five objectives are pursued: (1) establishing a statistical representation of local chemical fluctuations; (2) predicting probability distribution functions (PDFs) of unstable stacking fault (USF) energies based on the statistical representation; (3) developing probabilistic descriptions of Peierls barriers for different slip systems based on the PDFs of USF energies; (4) elucidating dislocation glide mechanisms using the probabilistic Peierls barriers; and (5) explaining and predicting deformation behavior of bcc CSAs with experimental validation, focusing on brittle-to-ductile transition and activation of slip multiplicity. The knowledge being generated in this project could open new pathways for improving the room-temperature toughness and ductility of bcc CSAs, thereby advancing their applications in industries vital to energy and national security, including nuclear energy, power generation, aviation and aerospace.

The statistical approaches being developed are also transferable to the study of probabilistic behavior for crystalline defects in other chemically complex material systems.

This project also includes a significant educational component that ignites passion and cultivates interest in material science and engineering (MSE) among students of various ages. Building on the scientific findings from the research component, the educational component offers multidisciplinary learning and training opportunities for undergraduate students across all levels, sparks early interest in MSE among high school students, and advances the integration of materials informatics into the MSE curriculum.

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.