Precision Nanocrystallization by CNC-Controlled Surface Mechanical Attrition Treatment

Despite their strength-ductility benefits, heterogeneously nanostructured materials are often difficult to manufacture and implement commercially. To realize their benefits in a processing-friendly manner, surface mechanical attrition treatment (SMAT) can be used to produce surface nanocrystallization on bulk parts through repeated impacts leading to cumulative deformation and microstructural refinement. This results in a gradient of grain size for improved strength and fatigue resistance. In most SMAT approaches, the randomness of surface treatment prevents the direct, quantitative study and control of individual impacts needed to directly connect processing variables with surface geometry and nanoscale grain development. This project utilizes surface impact with controlled energy and position to study the fundamentals of impact-induced microstructural phenomena in samples with both single impact sites and precisely patterned impact arrays. These methods provide new approaches to research heterogeneous microstructures and are directly scalable for industrial implementation. Both aspects and preliminary findings will be discussed.