The influence of beryllium addition on the microstructure and mechanical properties of Al-15%Mg2Si in-situ metal matrix composite

Highlights: → Primary Mg2Si particles refined by Be additions. → Be changed the shape of particles from an irregular shape to the faceted polygonal. → Pseudo-eutectic Mg2Si has mainly a fine fibrous structure in all specimens. → In specimens with Be, βAl-Mg-Be phase based on a β-Al3Mg2 phase was observed. → Be improved UTS and elongation values of the composite extremely. - Abstract: The effects of Beryllium (Be) on the microstructure and mechanical properties of Al-15%Mg2Si composite were investigated. The results showed that with the increase of Be content, the average size and volume fraction of primary Mg2Si particles decreases. Pseudo-eutectic Mg2Si has mainly a fine fibrous structure in both specimens with and without Be. However, in the samples containing Be, the path for crack propagation along cell boundaries is very tortuous. Meanwhile, βAl-Mg-Be phase based on a β-Al3Mg2 phase of the Al-Mg system was observed in specimens containing Be. It was found that with the addition of Be the ultimate tensile strength (UTS) and elongation values improved. A study of the specimen's fracture surfaces via scanning electron microscope revealed that Be increases the number of fine dimples and decohered Mg2Si particles.