MSE Seminar: Exploring Nanocrystalline Tungsten Alloys for Fusion Energy Platforms

Date/Time

02/20/2018
3:45 pm-5:00 pm
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Location

Rhines Hall, Room 125
549 Gale Lemerand Drive
Gainesville, FL 32611

Details

Join the Department of Materials Science and Engineering for light refreshments and a discussion lead by Dr. Jason Trelewicz of Stony Brook University.

The unique ability of grain boundaries to act as effective sinks for radiation damage plays a significant role in nanocrystalline materials due to their large interfacial area per unit volume. Leveraging this mechanism in the design of tungsten as a plasma-facing material, which will be subjected to high heat fluxes, elevated temperatures, aggressive particle and neutron fluxes, and high stresses, provides a potential pathway for enhancing its performance under fusion-relevant conditions. In this presentation, microstructure, phase evolution, and stability during self-ion irradiation is explored in nanocrystalline tungsten. Grain growth is shown to transpire through a discontinuous process at intermediate temperatures, which is coupled to an allotropic phase transformation of metastable β-tungsten to stable BCC α-tungsten. The addition of alloying elements stabilizes tungsten against the formation of this metastable phase while simultaneously inhibiting grain growth up to 1000°C. In situ self-ion irradiation also demonstrates that the addition of solute acts to stabilize the grain boundary network against irradiation-induced instabilities with insights into the underlying mechanisms presented from displacement cascade simulations. Nanoindentation results on helium implanted nanocrystalline tungsten will finally be summarized that reveal a new transition in the scaling of mechanical properties with fluence and attributed to the competition of softening due to grain boundary cavity formation with hardening from intragranular defect loop damage.

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Department of Materials Science and Engineering