Viscoplasticité à l'ambiante du titane en relation avec ses teneurs en oxygène et hydrogène

Abstract : The aim of the thesis is to study at the macroscopic, mesoscopic and microscopic scales, the effects of interstitials contents (oxygen and hydrogen) on titanium viscoplasticity at room temperature. At the macroscopic scale, the behavior was studied by tensile tests, strain rate jumps, relaxation and creep tests along to the rolling direction and the transverse direction. The materials show an anisotropic behavior due to a marked crystallographic behavior and a variation of the deformation modes when changing the loading direction. We note a hardening effect of oxygen and a discrete effect of hydrogen especially in the beginning of the plastic flow and during creep. The activated deformation mechanisms were observed in real time during in-situ tensile tests under an optical microscope or under SEM preceded by EBSD measurements of crystal orientations and accompanied by measures of local deformation fields and strain heterogeneity by digital image correlation. The tests highlight the predominance of prismatic glide. A solicitation along the transverse direction and an increase in the oxygen content promotes the basal glide and twinning. The critical resolved shear stresses of different slip systems increases with increasing oxygen contents. The analysis was also based on TEM observations of dislocations arrangements and twinning. The experimental data were used to identify a mean-field crystal viscoplasticity model.
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Submitted on : Tuesday, March 31, 2015 - 2:57:10 PM
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  • HAL Id : tel-01137807, version 1

Citation

Bassem Barkia. Viscoplasticité à l'ambiante du titane en relation avec ses teneurs en oxygène et hydrogène. Sciences de l'ingénieur [physics]. Ecole Polytechnqiue, 2014. Français. ⟨tel-01137807⟩

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