The effects of boron additions on the microstructure, hardness and tensile properties of in situ Al–15%Mg2Si composite

In this work the influences of Boron (B) content on the microstructure, hardness and mechanical properties of Al–15%Mg2Si composite were investigated. The results showed that with the increase of B content, the average size of primary Mg2Si particles decreased from ∼23 to ∼5 μm and the volume fraction of them decreased too, but the amount of alpha phase increased. It was found that with the addition of 0.3%B, the ultimate tensile strength (UTS) and elongation values reached from 252 to 273 MPa and 2.2% to 3.7%, respectively. It was revealed from hardness tests that B decreases the hardness values of the composite. Also, a small amount of Boride compounds formed as a result of the addition of B, which were the main reason of the decreasing of tensile properties at samples with high B.

► Primary Mg2Si particles refined by B additions.
► Some Borides were observed in specimens containing B.
► B decreased the hardness values of the composite.
► Addition of B improved UTS and elongation values of the composite.