Abstract
In this study, the in situ tensile test in SEM was used for online observation of the deformation process and fracture mechanism of mechanically alloyed Al composite; also different techniques, including Scanning Electron Microscope (SEM), the Energy-Dispersive X-ray Spectroscopy (EDX), Transmission Electron Microscopy (TEM), Electron Diffraction and High-Resolution Scanning TEM (HR-S/TEM) were used for identifying of secondary phases. Microscopic analysis revealed spherical grains in the interval of 30–40 μm. The presence of intermetallic secondary precipitates Al-Fe-Si, Mg₅Si₆, and Al-Fe(Mn,Si) nanoparticles was confirmed. The in-situ test showed that the first cracks were created on the sample's surface and simultaneously in triple junctions of grains. Also, decohesion of Mg₅Si₆ and Al-Fe(Mn,Si) nanoparticles and rupture of large Al-Fe-Si particles were observed. Subsequently, the cracks propagated along the grain boundaries. The fracture surface is complex and composed of two systems. Based on the performed analysis, the model of fracture mechanism was proposed.

Key words
mechanical alloying, Al composite, in-situ tensile test in SEM, fracture mechanism

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