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Instruments / Technical Area	Publication Details	Published
I13-1-Coherence I13-2-Diamond Manchester Imaging	Understanding the complex 3D structures of metal carbides for optimising the manufacture of Ni superalloys Jiawei Mi , Zhiguo Zhang Diamond Proposal Number(s): [9974, 13488, 22525] Show Abstract ▼ Abstract: Metal carbides are important microstructure constituents in polycrystalline Ni-based superalloys. They play a dominant role in determining the formation of cast defects and the strength of the alloys. However, the nucleation and growth dynamics of metal carbides, especially the true 3D network structure and morphology formed in different solidification conditions, have not been fully understood. Researchers focused on studying the 3D network structures and distribution of the metal carbides in a widely used IN713LC Ni superalloy. Their objective was to reveal the true 3D spatial information of the metal carbides and to understand the nucleation and growth dynamics of the metal carbides in different solidification conditions. The microtomography capability at the Diamond-Manchester imaging branchline (I13-2) offers a spatial resolution down to ~1 μm, while the ptychography capability at the Coherence branchline (I13-1) provides a spatial resolution down to ~30 nm. The research demonstrated clearly the advantage and technical potential of using the two complementary tomography techniques. The team found individual MC carbides distributed on the grain boundary between the gamma and gamma prime phases. The dominant growth directions of carbide branches were mainly determined by the local composition of the remaining liquid phase and geometric constraints. The metal carbides exhibited spherical, strip or network structure depending on the solidification cooling rates. The 3D characteristics of those structures were quantified for the first time. The findings can assist in optimising the manufacture of Ni superalloys to reduce casting defects. Scientists can use the rich 3D datasets to understand the initiation and propagation of crack at metal carbides during plastic deformation and service more quantitatively.	Jul 2021
	Synchrotron X-ray imaging and ultrafast tomography in situ study of the fragmentation and growth dynamics of dendritic microstructures in solidification under ultrasound Zhiguo Zhang , Chuangnan Wang , Billy Koe , Christian M. Schlepütz , Sarah Irvine , Jiawei Mi Acta Materialia 8 DOI: 10.1016/j.actamat.2021.116796 Open Access Show Abstract ▼ Abstract: High speed synchrotron X-ray imaging and ultrafast tomography were used to study in situ and in real time the fragmentation and growth dynamics of dendritic microstructures of an Al-15%Cu alloy in solidification under ultrasound. Under the studied condition, a strong swirling acoustic flow of ∼0.3 m/s was observed, resulting in efficient dendrite fragmentation due to thermal perturbation remelting plus mechanical fracture and separation effects. Acoustic flow fatigue impact and phase collision effects were found to play a minor role in causing dendrite fragmentation. Just 10 s of ultrasound application at the early stage of solidification produced ∼100% more dendrite fragments compared to the case without ultrasound, resulting in 20∼25% reduction in the average grain size in the solidified samples. Furthermore, the dendrite morphology and tip growth velocity were mainly affected by the initial dendrite fragment number density and their distribution. The systematic and real-time datasets obtained in near operando conditions provided valuable 4D information for validation of numerical models and assistance in developing optimisation strategy for ultrasound melt processing in industry.	Mar 2021
I13-1-Coherence I13-2-Diamond Manchester Imaging	Multiscale characterization of the 3D network structure of metal carbides in a Ni superalloy by synchrotron X-ray microtomography and ptychography Zhiguo Zhang , Jia Chuan Khong , Billy Koe , Shifeng Luo , Shi Huang , Ling Qin , Silvia Cipiccia , Darren Batey , Andrew J. Bodey , Christoph Rau , Yu Lung Chiu , Zhu Zhang , Jean-Christophe Gebelin , Nick Green , Jiawei Mi Scripta Materialia 193, 71 - 76 DOI: 10.1016/j.scriptamat.2020.10.032 Diamond Proposal Number(s): [9974, 13488, 22525] Open Access Show Abstract ▼ Abstract: Synchrotron X-ray microtomography and ptychography were used to characterize the 3D network structure, morphology and distribution of metal carbides in an as-cast IN713LC Ni superalloy. MC typed carbides were found to distribute mainly on the grain boundary between the matrix γ and γ' phase. The differences in solidification cooling rate had a minor influence on the volume fraction of the MC type carbides, but significantly affected the carbide size, distribution and network morphology. Depending on the local composition of the remaining liquid phase and geometric constraints, the carbides can form either spherical or strip or network morphologies. The research demonstrated clearly the advantage and technical potential of using the two complementary tomography techniques synergistically to characterize non-destructively complex multiple-phase structures in three dimensional space with a spatial resolution of ~30 nm.	Oct 2020

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