Influence des séquences de traitements thermiques sur les transformations structurales de l'alliage beta-cez : easpects cinétiques et morphologiques

Abstract : Phase transformation sequances of the beta-Cez and Ti-6246 titanium alloys were studied during several thermal treatments. Several technics were used to show the structural changes : transmission electron microscopy, X-ray diffraction patterns, electrical resistance and analytical electron microscopy. The different transformation sequences occurring during heating and (alpha+beta) annealing treatments were studied for three initial structures for the beat-Cez alloy, which present different degree of metastability obtained by different cooling rates from the stable beta temperature range. We showed that an initial structure (beta metastalbe + omega anisothermal) transforms in different ways depending on the heating rate. For a slow heating rate, the omega phase precipites in the beta transient matrix followed by alpha clusters ; which coarsen to form the alpha lamellae at higher temperatures; For a rapid heating rate (Vc=5 degrés C/s), the omega phase is not observed. However, a supposed orthorhombixal phase is observed nearby 450 C. Whatever the reating rate, a maximum of alpha phase content is observed up to 700 C. For temperatures higher than 700 C, the matrix homogenization and the dissolution and coarsening of alpha phase are observed, up to 830 C and continue during the annealing treatments. For an initial structures (beta metastable + alpha + alpha clusters) stemed from the beta range during a slow cooling (1,5 C/s), only a weak growth in the alpha phase is observed during heating up to 560 C. After this temperature, alpha clusters dissolve themselves up to 700 C. For temperature higher than 700 C, the same structural changes as for the previous initial microstructure are observed
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http://docnum.univ-lorraine.fr/prive/INPL_T_1994_FERREIRA_SANGUINETTI_R.pdf
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Submitted on : Thursday, March 29, 2018 - 1:40:49 PM
Last modification on : Monday, April 16, 2018 - 10:41:05 AM

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Ricardo Artur Sanguinetti Ferreira. Influence des séquences de traitements thermiques sur les transformations structurales de l'alliage beta-cez : easpects cinétiques et morphologiques. Autre [cond-mat.other]. Institut National Polytechnique de Lorraine, 1994. Français. ⟨NNT : 1994INPL093N⟩. ⟨tel-01752311⟩

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