Manufacturing Ductile Metallic Glasses Using Pattern-Seed-Spread Shear Band Engineering

Metallic glasses are a unique class of metals with a disordered atomic structure, unlike most conventional metals that exhibit an orderly crystalline arrangement. This structural difference gives metallic glasses exceptional strength and hardness but also makes them brittle and prone to sudden failure under tension—limiting their widespread application since their discovery in the 1960s. Researchers have been seeking ways to improve their ductility by introducing soft zones, known as shear bands, which can absorb stress and permit limited deformation. However, existing techniques lack precise control over the formation and behavior of these zones. This project supports fundamental research to develop a new, cost-effective processing method that creates carefully designed patterns of shear bands. This method enables metallic glasses to deform without catastrophic failure by tailoring their internal structure using laboratory-scale equipment not traditionally employed in metal manufacturing. The approach requires minimal capital investment and opens new pathways for processing these advanced materials. By enhancing ductility and enabling structural control, the project broadens the application potential of metallic glasses for advanced engineering technologies. It also contributes to strengthening U.S. manufacturing capabilities and advancing national goals in science, innovation, and economic competitiveness. University students involved in this research will gain valuable training for future careers in advanced materials and manufacturing. Despite their exceptional strength and elastic strain limits, metallic glasses (MGs) have seen limited commercialization due to their near-zero tensile ductility. Shear bands facilitate localized stress relaxation in metallic glasses by forming soft regions within a hard matrix, but controlling their formation and evolution remains a major processing challenge. Broad application of MGs requires processing strategies capable of systematically engineering shear bands to significantly enhance tensile ductility. This project introduces a novel approach for shear band engineering through strategic patterning, seeding, and spreading in metallic glasses, using an innovative combination of Rockwell indentation and high-pressure torsion – techniques not previously recognized for processing metallic glasses. To demonstrate the applicability and effectiveness of this approach, the study will focus on Cu-based and Zr-based MGs, both of which possess high glass-forming ability and are relevant to a wide range of engineering applications. By combining shear band engineering, multiscale microstructural characterization, microscope-based in-situ mechanical testing, and high-performance molecular dynamics simulations, this project will advance the fundamental knowledge of (i) the relationships between processing conditions and shear band microstructure, (ii) the mechanisms underlying shear band-induced tensile ductility, and (iii) microstructure design strategy to overcome the long-standing strength-ductility tradeoff in metallic glasses. 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.