Composites eutectiques et hypo-eutectiques Mg/gamma-Mg17Al12 : microstructures et comportement mécanique à l’ambiante et à chaud

Abstract : For a 31 at.% Al content, the Mg-Al system shows a eutectic mixture formed by Mg fibers embedded in a matrix of a complex metallic phase, the gamma-Mg17Al12 phase. During the thesis, eutectic and hypoeutectic Mg-Al alloys have been prepared by solidification to obtain in situ composites with various volume fractions of complex phases. These alloys appear as a new kind of composites containing complex metallic phases. The mechanical behaviour at room temperature shows that plasticity is possible even for high volume fraction of the gamma-Mg17Al12 phase, a phase which is very hard but brittle at room temperature. At high temperature (250°C-350°C), for all composites, compression tests exhibit a stress peak followed by a pronounced softening. Microstructural studies suggest that the room temperature plasticity is related to the fine scale microstructure of the complex metallic phase gamma-Mg17Al12. At high temperature, the mechanical behavior results preferentially from dynamic recrystallisation and grain boundary sliding.
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Souad Benrhaiem. Composites eutectiques et hypo-eutectiques Mg/gamma-Mg17Al12 : microstructures et comportement mécanique à l’ambiante et à chaud. Matériaux. Université de Grenoble, 2014. Français. ⟨NNT : 2014GRENI094⟩. ⟨tel-01228518⟩

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