Spatiotemporal Defect Dynamics and Microstructural Hierarchy under Extreme Shear

Understanding the dynamic microstructural evolution of materials under extreme shear deformation is crucial for advancing severe plastic deformation processing, tribology, and geology1-8. Despite decades of research leveraging ex situ experimental analysis and simulations, significant knowledge gaps persist regarding critical processes like grain boundary sliding and changes in dislocation density and vacancy concentration under high-speed shear3,9,10. This is largely due to the challenges of capturing real-time microstructural changes during rapid shear deformation11. To address this, here we developed a high-speed rotational diamond anvil cell for in situ synchrotron X-Ray diffraction studies. Integrating these in situ insights with multimodal ex situ characterization and multiscale computational simulations, we unravel the mechanisms of defect evolution, hierarchical microstructural refinement, and deformation-induced intermixing in a model Cu–Ni powder mixture. Capturing these rapid, previously hidden, phenomena pave the way for fresh insights into material behavior under extreme conditions, revealing fundamental mechanisms of deformation that were hitherto inaccessible.