Étude des Transformations de Phase dans des Alliages base TiAl faiblement alliés en Silicium

Abstract : The goal of this study is the understanding of the influence of silicon on the microstructure of TiAl-based alloys. Small additions of silicon are actually known to improve the heat resistance of these intermetallics. It is shown here that silicon segregates strongly at the microscopic scale during solidification, leading to the apparition of primary silicides in the interdendritic regions. After a study of this segregation, homogenization heat treatments were performed in order to focus on a quantitative study of the solid-solid transformations occuring in these alloys. Thus, silicide precipitation was observed at the gamma/alpha2 interfaces in homogeneous lamellar structures. However, the lamellar structure undergoes its own evolution as the silicides nucleate and grow. The links between these simultaneous transformations are shown by our experimental results, then modelled through simple considerations. As a conclusion, mechanical tests on controlled microstructures give some trends on the influence of silicon on the high temperature mechanical properties of TiAl alloys
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Antoine Paris. Étude des Transformations de Phase dans des Alliages base TiAl faiblement alliés en Silicium. Autre. Université de Lorraine, 2015. Français. ⟨NNT : 2015LORR0340⟩. ⟨tel-01752262⟩

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