Research

Upper: Atom-probe reconstructions of a W-25at.%Re alloy. Only Re atoms are shown. (a) before implantation and (b) after irradiation with 2MeV W ions at 500 °C to 2.8 dpa. Lower region: The concentration distributions show random distribution before and clustering of Re after irradiation.

Irradiation damage studies

Fusion engineering materials will be exposed to extreme irradiation fluences (>100 dpa). We investigate irradiation damage phenomena including solute clustering phenomena using Atom Probe (left) and helium gas accumulation using Transmission Electron Microscopy (right).

Bright Field contrast TEM images of WC-FeCr after irradiating with 6KeV He ions to ~50 at.% and ~15 dpa at 25 °C: (a) large area; (b) underfocus close-up ofWC/M6C; (c) of WC/FeCr/Cr-C region, showing preferential growth of hemispherical He bubbles.
Oxidation resistance

The first-wall materials must possess good oxidation resistance if it will withstand a loss-of-coolant accident scenario. We study corrosion performance using oxy-acetylene torch testing (right) and have developed and patented corrosion barriers for candidate WC-based materials (left).

SEM cross-sectional image of a Si-rich coating developed by pack cementation. The coating forms a two-part structure with WSix-rich inner layer and a FeSix outer layer, which provides excellent protection.

Oxyacetylene flame tests simulating fusion reactor accident scenarios. Heat flux conditions of 1, 1.3, 2.1, and 3.5 MW/m2 leading to front-facing temperatures of ~900, 1100, 1300 and 1400 oC
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High temperature flexural testing of W2B-W composites to identify the ductile-to-brittle transition temperature. (a) Maximum deflection before fracture; (b): Photograph of typical sample after testing

Thermomechanics

Fusion materials may be exposed to >1000 oC, making high temperature mechanical behaviour important. We try to understand potential mechanisms of failure, using techniques like dynamic flexural testing (left) and compressive creep (right).


Compressive testing of WC-FeCr composites to identify mechanistic retimes, showing 3 regimes of stress dependence, n. 
Material development

The extreme conditions of a fusion reactor exceed the capabilities of industrially available materials, requiring new structures and composites to be engineered. We have developed metal-ceramic composite shielding materials, including W2B-W (left) and WC-FeCr (right) in which the metallic phase offers improved fracture toughness and manufacturability.

Two W2B-W composites with different boron contents, W-16B and W-30B, which result in a trade-off between shieilding performance and damage tolerance. (a) EBSD phase maps, revealing the different boride phase fractions; (b) SEM images in BSE mode revealing the grain structure.

Top left – HAADF TEM image showing WC (light) and FeCr (dark). Smaller images – EDS dot maps showing W (red), Fe (blue), Cr (purple), C (green) and their sum (Layered). Cr-carbides are indicated by dotted circles and M6C by arrows.