Zirconium alloys

Zr-based alloys

This research is part of the nuclear fission activity within the FIM Group. The 3D atom probe technique has allowed new insight into areas of metallurgy that have previously been extensively investigated over several decades. My recent work with the group has centred on the analysis of zirconium alloys using 3DAP. Zirconium alloys are used in the nuclear industry as fuel rod cladding. In new high performance reactors the break-down in corrosion resistance of these alloys is becoming the limiting factor in the amount of fuel that can be used before the rod must be replaced. Pressurised water reactors (PWR) currently make use of just a third of the fuel in each rod before they must be removed and reprocessed. Improving our understanding of the failure of these materials should allow us to improve their performance, a matter of high economic and environmental importance.

The examples shown above and below demonstrate the nano-chemical resolution of the atom probe and two such insights that have been gained into the metallurgy of these alloys: A previously uncharacterised sub-oxide layer between the metal and bulk oxide (which has now also been shown using high resolution electron microscopy), and the direct observation of the segregation of solute to grain boundaries.

3D atom maps of a grain boundary region of ZIRLO (a) showing all ions, (b) showing the segregation of iron, and (c) the segregation of and niobium at the interface. The grain boundary occupies a larger area than would be expected in the reconstruction space; this is due to local magnification effects arising from the atom probe specimen geometry [1].

For more details on this project, please contact Prof. George Smith.

[1] D. Hudson and G. D. W. Smith, Initial Observation of Grain Boundary Solute Segregation in a Zirconium Alloy (ZIRLO) by 3D Atom Probe. Scripta Mat., 61 4 (2009) 411-414