Grain Growth in Niobium for Superconducting Radio Frequency Cavities

Abstract

This project explores the grain growth characteristics and grain morphology of bulk niobium (Nb) processed by severe plastic deformation (SPD). This report deals with factors affecting grain growth and recrystallization: purity, temperature, and time. Several heavily cold worked samples of varying purities (99.9X% and 99.99X%) were heat treated at varying temperatures and times to reveal grain growth behavior. Results presented include optical micrographs and grain characterizations in terms of size and morphology. Preliminary results indicate a significant amount of grain size banding in the recrystallized microstructures in the RG niobium. However, the RRR did not have the same banded microstructure. This may be an effect of the processing route or a result of the grain growth behavior in Nb.