Browsing by Author "Lewtas, Heather"

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    Functionally graded structures of refractory metals by Wire Arc Additive Manufacturing
    (Maney Publishing, 2019-03-11) Marinelli, Gianrocco; Martina, Filomeno; Ganguly, Supriyo; Williams, Stewart W.; Lewtas, Heather; Hancock, David
    Functionally graded components are usually preferred for severe and critical service conditions, thanks to the possibility of achieving different complementary material properties within the same structure. Wire + Arc Additive Manufacturing is an emerging technology which lends itself well to the production of sound graded structures. In this study, an integral structure of two functional gradients, namely tantalum to molybdenum, and molybdenum to tungsten, was successfully deposited. A linear gradient was observed in both composition and hardness. Microstructure, elemental composition and hardness were characterised as a function of position, and discussed. The study demonstrates that WAAM has the potential to successfully deposit functionally graded structures of refractory metals, obtaining controlled properties
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    Microstructure and thermal properties of unalloyed tungsten deposited by Wire + Arc Additive Manufacture
    (Elsevier, 2019-05-01) Marinelli, Gianrocco; Martina, Filomeno; Lewtas, Heather; Hancock, David; Mehraban, Shahin; Lavery, Nicholas; Ganguly, Supriyo; Williams, Stewart W.
    Tungsten is considered as one of the most promising materials for nuclear fusion reactor chamber applications. Wire + Arc Additive Manufacture has already demonstrated the ability to deposit defect-free large-scale tungsten structures, with considerable deposition rates. In this study, the microstructure of the as-deposited and heat-treated material has been characterized; it featured mainly large elongated grains for both conditions. The heat treatment at 1273 K for 6 h had a negligible effect on microstructure and on thermal diffusivity. Furthermore, the linear coefficient of thermal expansion was in the range of 4.5 × 10−6 μm m−1 K−1 to 6.8 × 10−6 μm m−1 K−1; the density of the deposit was as high as 99.4% of the theoretical tungsten density; the thermal diffusivity and the thermal conductivity were measured and calculated, respectively, and seen to decrease considerably in the temperature range between 300 K and 1300 K, for both testing conditions. These results showed that Wire + Arc Additive Manufacture can be considered as a suitable technology for the production of tungsten components for the nuclear sector.