Enhancement of Nanostructured Ferritic Alloy 14YWT Properties via Heat Treatment for Post-Consolidation Processing

The nanostructured ferritic alloy 14YWT is a promising candidate for in-core use in generation IV nuclear reactors, due to a dense dispersion of insoluble, ultrafine-scale Y-Ti-O nano-oxides, which provide a high degree of irradiation tolerance and thermal stability. This study investigates the effects of heat treatment on the workability of 14YWT, along with the effect of processing history on abnormal grain structures and radial microstructural uniformity. In this study, a 14YWT rod consolidated at 850 degrees C was heat treated in argon at 1100 degrees C, 1150 degrees C, 1200 degrees C, or 1250 degrees C for 1 or 8 hours and changes in mechanical properties and microstructure were examined using microhardness and electron backscattered diffraction (EBSD). Two distinct types of large abnormal grains were observed, each with unique processing origins, including one with high and the other with low strain energy. Consolidation via direct extrusion resulted in radial microstructural gradients, where the center of the rod was softer with larger grain sizes and lower strain energies. These gradients persisted and intensified throughout heat treatment. Based upon this work, the recommended heat treatment for increased workability with minimal microstructural change is 1150 degrees C for 1 hours.

Automated summary

The study investigates the effects of heat treatment on the workability of 14YWT, as well as the impact of processing history on abnormal grain structures and radial microstructural uniformity. It was found that consolidation via direct extrusion resulted in radial microstructural gradients, and the recommended heat treatment for increased workability with minimal microstructural change is 1150 degrees C for 1 hour.