Browsing by Author "Yu, S"

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    The characterisation and formation of novel microstructural features in a Ti−Nb−Zr−Mo−Sn alloy manufactured by Laser Engineered Net Shaping (LENS)
    (Elsevier, 2021-01) Zhu, HL; Wang, ZY; Muránsky, O; Davis, J; Yu, S; Kent, D; Wang, G; Dargusch, MS
    Novel microstructural features were found in the Ti−Nb−Zr−Mo−Sn alloy manufactured by Laser Engineered Net Shaping (LENS). Examination of the microstructure showed that the fabricated sample exhibits a layered morphology with arced deposit boundaries. Novel distributions and morphologies of various phases including β, α, α'' and ω were detected in the LENS-manufactured part which substantially differ to conventionally processed alloy counterparts. The β grains and subgrains spread over multiple deposits and layers, aligned to the build direction, forming a complex network microstructure comprising large highly textured columnar grains aligned to β phase <001> orientations. The α precipitates have needle-like shapes and are widely distributed across a majority of the deposited layers, whereas the nanoscale ω particles were present in regions absent of α precipitation. Localised, massively transformed α'' phase with a very long and curved rod-like shape and substantial surface defects was identified. The formation of these novel microstructural features is investigated and discussed in the context of the characteristics of the LENS fabrication process. The microstructures are attributed to the complex thermal history in the unique deposit-by-deposit and layer-by-layer method employed during LENS additive manufacturing in conjunction with the complex precipitation behaviours exhibited by TiNb-based alloys. The characteristics and formation mechanisms of the LENS-manufactured Ti−Nb−Zr−Mo−Sn alloy microstructures revealed here provide a basis to optimize LENS and post-LENS heat treatment processes to optimize microstructures for improved performance. © 2020 Elsevier B.V