Preparation of TEM Samples from Neutron-Irradiated Ferritic/Martensitic Fe-Cr Alloys
EMSL Project ID
47196
Abstract
Ferritic/martensitic steels, particularly those modified to include nanoscale oxide dispersions, show great promise use in structural applications in fusion reactors. However, generation of He through transmutation-induced reactions, coupled with displacement damage, lead to significant decreases in the ductile-to-brittle transition temperature and an overall loss of ductility. Studies have therefore been undertaken to investigate the role of He accumulation in neutron-irradiated ferritic/martensitic Fe-Cr steels with various alloying constituents such as W and V. Samples of various F/M steels (F82H, MA957, Eurofer97, and 12YWT), coated with a 1-4 µm layer of NiAl, were irradiated in the HFIR reactor. He is injected from the Ni-Al layer when the Ni undergoes transmutation, effectively producing a uniform deposition layer 5-8 µm under the NiAl coating. The layer thickness and neutron dose yield He/dpa ratios in the range of 5-50 appm He per dpa. Irradiation temperatures included 300, 400 and 500°C. Previous characterization of lower dose materials revealed that the presence of a high density of very fine He bubbles >2 nm in diameter, and in some cases a significant density of faceted voids. Alloys with oxide dispersions incorporated into the microstructure showed a significant refinement of the bubble distribution, suggesting that the oxide particle interfaces successfully serve as He-vacancy recombination sites and trap He. Higher dose conditions are now available, but their neutron dose is high enough to warrant a different specimen preparation approach. The proposal requests the use of the Quanta 3D FIB-SEM to prepare TEM samples from the region of uniform He deposition to characterize the He distribution, He bubble and void characteristics.
Project Details
Start Date
2012-02-24
End Date
2014-02-07
Status
Closed
Released Data Link
Team
Principal Investigator
Team Members