Etude de la contribution de la technique spark plasma sintering à l'optimisation des propriétés mécaniques de l'alliage de titane TA6V

Abstract : The cost prices of the titanium alloys limit their applications to strong added value fields. The decrease of the pieces shaping costs while mastering microstructures and mechanical properties is an important issue. Shaping processes from powder metallurgy as Spark Plasma Sintering (SPS) can allow to reach these goals. The first moments of the sintering were studied according to the initial compactness of the granular body. When the latter is low, the area of necks between granules, highlighted by microtomography, are bigger. These observations can be explained by the fact that current densities at contact points are higher when the contact areas are lower. Furthermore, the very close final densities in spite of the different initial compactness let think that the mechanisms in action during sintering are different. An electro-thermal and mechanical modelling by finished element allowed to describe in a very realistic way the densification of the TA6V. The densification law of the material was configured by means of creep tests programmes performed dine the SPS chamber as well as of compaction tests of the granular body. Ways of improvement of the model were also proposed. In the last part of the word, a panel of microstructures obtained by SPS of TA6V as well as a scale transfer from the small cylindrical samples towards more massive and complex shapes was studied. Furthermore, the tensile properties of near-net-shape specimens were characterised. Domains (temperature and pressure) of dense, homogeneous and repeatable microstructures obtaining were identified. The scale transfer reveals that the SPS repeatability is both validated in terms of microstructures and mechanical properties of the densified specimens. Furthermore, tensile properties are at the same level as the forged materials, in particular an elongation at break of about 13%.
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Ugras Kus. Etude de la contribution de la technique spark plasma sintering à l'optimisation des propriétés mécaniques de l'alliage de titane TA6V. Matériaux. Université Paul Sabatier - Toulouse III, 2017. Français. ⟨NNT : 2017TOU30131⟩. ⟨tel-02274980⟩

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