Impact of annealing at 1000°C in flowing He with low O₂ concentration on the room temperature tensile properties of Mo alloys

Technical Report · Thu Sep 01 04:00:00 EDT 2022

DOI:https://doi.org/10.2172/1973347· OSTI ID:1973347

Dryepondt, Sebastien ^[1]; Willoughby, Adam ^[1]; Johnston, Brandon ^[1]

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1. Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)

NorthStar is developing an accelerator-based technology to produce the medical isotope Mo-99. A previous ORNL report (ORNL/SPR-2022/2490) studied the oxidation behavior of Mo in flowing He with low oxygen content at 800°C and 1000°C and it was shown that an O₂ concentration lower than ~5ppm (μ1/1) is required to achieve acceptable oxidation rates for wrought or powder metallurgy (PM) Mo. Oxidation may also impact the mechanical properties of Mo and this report summarizes tensile results at room temperature on wrought and PM Mo before and after exposure at 1000°C in flowing He with O₂ concentration varying from 1 to 15 ppm O₂. It was found that oxidation at 1000°C results in a significant decrease of Mo strength and ductility with brittle intergranular fracture surfaces, likely due to the segregation of oxygen at grain boundaries. For the PM Mo material, the decrease in strength and ductility was also observed after annealing in vacuum at 1000°C, indicating that the diffusion of the oxygen trapped in the material pores to grain boundaries after 20-100h at 1000°C is sufficient to embrittle the material. Finally, initial results on actual aMo and high-density disks provided by NorthStar revealed the lack of ductility of the materials due to the specific disk microstructure.

• Research Organization: Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
• Sponsoring Organization: USDOE National Nuclear Security Administration (NNSA)
• DOE Contract Number: AC05-00OR22725
• OSTI ID: 1973347
• Report Number(s): ORNL/SPR--2022/2641
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE