Effect of AlB2–Mg interaction on the mechanical properties of Al-based composites

A series of Al-based composites with a matrix containing 2.5 wt.%Cu and 1 wt.%Mg, and reinforced with Al diborides was manufactured and characterized via microscopy and mechanical testing. The impact resistance of the composites revealed interaction between AlB2 dispersoids and Mg originally present in the Al matrix. An unexpected increase in the absorbed impact energy of composites with diborides prompted complementary experiments leading to this finding. Hardness tests were correlated to those results and provided further evidence of the interaction between Mg and the dispersoids. Additional energy dispersive spectroscopy (EDS) analysis and X-ray diffraction tests supported with crystal modeling demonstrated that Mg effectively diffused into the AlB2 crystal producing a doped structure with an Al1−xMgxB2 formula where x lies between 0.08 and 0.15.