Browsing by Author "Kawasaki, M"

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    Martensitic phase transformation and deformation behavior of Fe–Mn–C–Al twinning-induced plasticity steel during high-pressure torsion
    (Wiley Online Library, 2014-02-05) Yan, K; Bhattacharyya, D; Lian, Q; Kabra, S; Kawasaki, M; Carr, DG; Callaghan, MD; Avdeev, M; Li, HJ; Wang, Y; Liao, XZ; Langdon, TG; Liss, KD; Dippenaar, RJ
    The transformation between the face centered cubic austenitic and hexagonal close-packed martensitic phases during high-pressure torsion processing was observed in a Fe–Mn–C–Al twinning-induced plasticity steel. This phase transformation was not found in the same material processed by unidirectional compressive and tensile deformation. Initiated by the high-pressure loading, the martensite phase initially increased with torsional strain but diminished subsequently. Texture evolution of the austenitic phase was compared with the ideal texture distribution of face-centered cubic materials after shear deformation.© 2014, WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
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    Neutron and x-ray studies of TiAl-Nb intermetallics undergone high-pressure torsion
    (Australian Institute of Nuclear Science and Engineering, 2016-11-29) Li, X; Dippenaar, RJ; Kawasaki, M; Liss, KD
    High-pressure torsion is a severe-plastic-deformation technique rendering the bulk metallic material into an ultrafine microstructure. Not only the application of high pressure in the 6 GPa range bears potential for phase transformation, moreover huge plastic shear strains of 10 to 100 is achieved by torsion processing. In a first study, pellets of y-based Ti-45Al-7.5Nb have been processed under 6 GPa at room temperature, (i) with pressure loading and unloading only, (ii) with 5 turns of torsion and (ii) 10 turns. The material, which usually is brittle and hard to deform, was successfully processed and showed ductility under these conditions. First investigations by neutron and X-ray diffraction are presented, emphasizing the complementarity of both kinds of quantum beams. While X-rays determine the overall structure, such as close-packing, neutrons are particularly sensitive to the order parameter in the constituting y-TiAl and a2-Ti3Al intermetallic phases. It is found that the atomic order decreases on larger amount of processing. Also structural transformations regarding the atomic packing take place. These preliminary examinations open routes for physical understanding and recovery of the occurring crystallographic transformation and microstructural arrangements.