EUROPEAN CONGRESS AND EXHIBITION ON ADVANCED MATERIALS AND PROCESSES - EUROMAT 2021

The present study investigates the effect of room temperature high pressure torsion (HPT) processing of pure Nb, Nb-1Zr (wt.%) and Nb-1Zr-0.1C (wt.%) on the microstructure, texture and mechanical property evolution. Being a ductile BCC material, and due to the application of a high hydrostatic pressure, the disk-shaped samples deformed without the formation of microcracks. X-ray line profile analysis using convolutional multiple whole profile (CMWP) fitting showed the deformed samples exhibited a nanocrystalline microstructure with high dislocation density. EBSD micrographs showed that with the application of higher strain, not only did the population and misorientation angle of the high angle grain boundaries increase but also an increase in the fraction of dynamically recrystallized grains was observed. Microhardness results showed an increase in strength with alloying additions in Nb-1Zr (wt. %) and Nb-1Zr-0.1C (wt. %). TEM imaging of HPT deformed Nb-Zr-C alloy showed the presence of fine precipitates. APT analysis was done to find the composition of the precipitates. Bulk texture measurements by XRD showed subtle differences in the as deformed textures of the three alloys. The {112}<111> simple shear texture component was the strongest in all the deformed samples. However, the textures exhibited a cyclic strengthening and weakening tendency due to dynamic recrystallization. The grain size determined by EBSD, dislocation density from XLPA-CMWP, precipitate size and distribution from TEM, and texture strengthening were used to deconvolute the strengthening contributions acquired from plastic deformation, solid solution, precipitates and simple shear textures in the three alloys.