Optimisation des conditions de mise en oeuvre de la jonction Ti/Al par FSW : influences des propriétés mécaniques et metallurgiques des interfaces

Abstract : These PhD works are about heterogeneous friction stir welding between titanium (Ti grade II) and aluminum (AA1050). Research is focused on lap joining configuration in order to limit the process stress. Taguchi's design of experiments determined parameters influence for a defectless welded junction. The rotational speed of the tool has been identified as the parameter which influences the most the defects generation. Parameters combinations are linked to a heat input coefficient. The thermal conductivity difference between the two material leads to a thermal gradient in the thickness up to 80°C. No junction mechanical strength optimization has been revealed by tensile and bending tests.Microstructural analyses were performed on the welded junction in order to understand the mechanical properties. One single intermetallic compound TiAl3 nucleates in the titanium volume and ensures interface chemical continuity. Further analyses with EBSD (SEM) supplemented by ASTAR™ (TEM) method for the smaller scales have completed the observations. The process generates aluminum severe plastic deformation which induces a grain size reduction with a gradient following the configuration thicknessAll observations brought clues to understand friction stir welding phenomenon leading to microstructural evolution to realize a better link between resulting microstructure and macroscopic properties.
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Florent Picot. Optimisation des conditions de mise en oeuvre de la jonction Ti/Al par FSW : influences des propriétés mécaniques et metallurgiques des interfaces. Matériaux. Normandie Université, 2018. Français. ⟨NNT : 2018NORMC283⟩. ⟨tel-02279601v2⟩

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