In-situ Studies of Erosion in Ultrafine-Grained and Nanocrystalline Metals

About This Grant

NON-TECHNICAL SUMMARY Impact-induced erosion from high-speed particle collisions occur at the microscale in critical systems such as jet engine turbine blades, satellites, and chemical pipelines. Ultrafine-grained and nanocrystalline metals, with their superior mechanical properties hold promise for improved erosion resistance, but the underlying mechanisms remain poorly understood. This award is addressing this gap through in-situ studies of supersonic impact-induced erosion in metals across a broad range of grain sizes, from tens of microns down to the nanometer scale. Using in-situ supersonic impact testing, the project examines material response at small scales and extreme strain rates, focusing on understanding the key hardening and softening mechanisms. This research is enabling the design of new materials that can prevent erosive failures, with the potential to strengthen the national defense, automotive, aerospace, and energy industries. This activity is also engaging K–12 students to strengthen the STEM pipeline and enhance national competitiveness. This project supports education and workforce development by introducing new curricula, raising student awareness of emerging opportunities in metals, and connecting industry with the latest research advances. TECHNICAL SUMMARY Deformation localization under supersonic impact is a precursor to erosive failure and is governed by the competition between hardening and softening mechanisms at extreme strain rates. The overall goal of this project is to systematically investigate these mechanisms in ultrafine-grained and nanocrystalline metals, within a strain-rate regime that is largely inaccessible to conventional mechanical testing and as as result, remains significantly underexplored. This research further refines a novel combination of laser-induced microprojectile impact testing and spherical nanoindentation to isolate and quantify dislocation–phonon interactions which are hypothesized to be the primary hardening mechanism under erosive impact conditions. This integrated approach is being used to study how grain size influences ballistic dislocation transport and its role in impact-induced hardening. In parallel, the study is also exploring the microstructural origins of softening, focusing on two key mechanisms, adiabatic shear instability and grain coarsening. Moreover, this project is examining how these are affected by grain size. High-resolution cross-sectional microscopy is being used to characterize microstructural evolution while providing mechanistic insight. Together, this investigation is revealing how the interplay between hardening and softening mechanisms govern a material’s resistance to erosive failure and offer design guidelines to help prevent such failures. This project also supports education and workforce development by introducing new curricula, raising student awareness of emerging opportunities in metals, and connecting industry with the latest research advances. 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.