Grain Boundary Analysis of U-6Nb Binary Uranium Alloy
EMSL Project ID
51802
Abstract
In applications of uranium - 6 wt% niobium (U-6Nb) important to NNSA, its mechanical properties are exploited by engineers to achieve desirable mechanical response. When U-6Nb is heated for short times (<2 hours) at low temperatures (200 ?C), it exhibits a permanent increase in yield strength and accompanying embrittlement or reduction of failure strain. The higher strength achieved via the aging treatment is explicitly relied upon in the engineering design of the system. However, despite decades of research, the physical reasons for this change in mechanical performance of the alloy after low temperature thermal exposure are unknown. Furthermore, Furthermore, there appears to be a process correlation; the mechanical behavior after low temperature heating is different for cast, wrought and additively manufactured U-6Nb. Thus microstructural characterization at the nanoscale is critical to understanding the reasons for these differences is equally critical to the establishment of unconventional and/or modern processing methods for U-6Nb. Analysis of similar material systems by others would suggest depletion of intragranular Nb, in which case Nb is likely enriched at the grain boundaries. However, analysis by our collaborator at LLNL has not been able to confirm Nb enrichment at grain boundaries using transmission electron microscopy (TEM), likely due to low relative Nb concentrations. The most promising technique to address such potentially fine elemental variations at sub-?m scales is atom probe tomography (APT). This project seeks to utilize APT to better understand variations in Nb and trace element concentrations at targeted grain boundaries of U-6Nb that has undergone varying metallurgical processing methods.
Project Details
Start Date
2021-01-01
End Date
2021-09-30
Status
Closed
Released Data Link
Team
Principal Investigator
Team Members