Influence of Al₂O₃ Particles Weight Fraction on Fracture Mechanism of AZ61 Mg-Al₂O₃ System Studied by In Situ Tensile Test in SEM

In situ observation of AZ61 Mg alloy with 1 and 5 wt% of Al₂O₃ in the scanning electron microscopy was performed to study influence of the weight fraction of Al₂O₃ particles on the deformation and fracture mechanism during tensile test. Structure of the experimental materials was also analysed; microstructures were heterogeneous, with randomly distributed globular Al₂O₃ particles (average diameter of 25 nm) and Mg₁₇Al₁₂ intermetallic phase (average diameter of 0.4 μ m). It was shown that during tensile deformation the failure of Mg₁₇Al₁₂ particles and decohesion of the matrix-Al₂O₃ particles interphase boundary started simultaneously. Decohesion resulted from the different physical properties of matrix and Al₂O₃ particles. The influence of the Al₂O₃ weight fraction on the final fracture was evident; for material with 5 wt% of Al₂O₃, the fracture surface was approximately perpendicular to the loading direction and for material with 1 wt% of Al₂O₃ was at 45° angle. Fracture surface had transcrystalline ductile character.