Papers by Author: Chris H.J. Davies

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Authors: F. Xiong, Chris H.J. Davies
Authors: P.J. Hurley, Barry C. Muddle, Peter D. Hodgson, Chris H.J. Davies, Bradley P. Wynne, P. Cizek, M.R. Hickson
Authors: P. Cizek, Bradley P. Wynne, Chris H.J. Davies, Barry C. Muddle, Peter D. Hodgson, Allan Brownrigg
Authors: Michael Battaini, Elena V. Pereloma, Chris H.J. Davies
Abstract: This paper investigates the changes in deformation mechanisms of commercially pure titanium over a range of temperatures for different orientations relative to the initial rolling texture. Samples from grade 1 titanium plate were tested in plane strain compression (PSC). Extremes of orientation relative to the predominant split basal texture were tested at temperatures from 25°C to 700°C. Specimens were subsequently examined using X-ray texture analysis and electron back-scatter diffraction (EBSD). Changing the orientation resulted in substantial yield stress anisotropy. This was found to be largely related to the orientation of the dominant texture relative to the most favorable orientation for the easiest slip mode (prism slip), and significantly but to a lesser extent on differences in twinning behaviour. The most important difference in twinning was the operation of {1012} tensile twinning in c-axis tension and {1122} compression twinning in c-axis extension. Calculations indicated that at low temperature both of these twinning modes accommodate a significant amount of strain. Twinning was also found to be the most significant factor affecting work hardening behaviour, with reorientation hardening occurring for some sample orientations. As temperature was increased above ~350°C {1011} twinning became the dominant twinning mode, but its contribution to the strain was not as large as the low temperature twinning modes, and the total amount of twinning decreased with temperature. The decrease in twinning with increasing temperature led to a reduction in the difference in work hardening behaviour. The quantitative information gathered in the course of this work is discussed in the context of mechanical property prediction.
Authors: Mark Easton, Chris H.J. Davies, Matthew R. Barnett, Franka Pravdic
Abstract: A recent trial investigated the effect of solidification grain refinement of billet on the grain refinement and properties of alloy ZM20. It was found that even at levels of 0.4Mn, significant grain refinement could be obtained when 0.7Zr was added. At 0.2Mn grain sizes as low as 60μm were obtained. Billets of Mg-2Zn-0.2Mn with four different grain sizes, due to different Zr and cooling rates were then cast via vertical direct chill casting and extruded conventionally. Benefits of grain refinement of the billet on extrusion were found to be a slight increase in the size of the operating window, and a reduction of the grain size in the extrudate. However, the effect of the reduction in extrudate grain size due to refinement of the billet was small compared with the amount of grain refinement obtained due to recrystallisation on extrusion.
Authors: Cheng Fan Gu, László S. Tóth, Benoît Beausir, Tim Williams, Chris H.J. Davies
Abstract: A comparative experimental and simulation study of oxygen-free high conductivity copper produced by equal channel angular pressing (ECAP) one-pass has been carried out by using electron backscatter diffraction (EBSD) and a recently proposed grain refinement model. The grain size and misorientation distributions were extracted from the EBSD measurements. It was found that the microstructure in the ECAP deformed copper was much more refined on the TD plane. The grain size observed experimentally can be fairly well predicted by the grain fragmentation model.
Authors: M. Staiger, Chris H.J. Davies, Peter D. Hodgson, B. Jessop, Allan Brownrigg
Authors: Adrian Grosvenor, Chris H.J. Davies
Authors: Ji Kang Zhong, Matthew S. Dargusch, Chris H.J. Davies
Abstract: The hot deformation behaviour of the alpha / beta Ti-6Al-4V alloy was investigated at various temperatures and strain rates by means of compression and torsion tests. As expected, the peak flow stress increased with increasing strain rate and decreased as the initial sample temperature was increased. The different flow behaviours observed are discussed in terms of the volume fraction of each phase. The dual phase Ti-6Al-4V alloy was assumed to be a composite material containing a soft phase and a hard phase. By taking into consideration the phase-to-phase interaction and volume fraction change with temperature, constitutive models are proposed to simulate the deformation behaviours. By application of the rule of mixtures the modelled yield stresses showed good agreement with the experiment results.
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