Distribution of the microalloying element Cu in B4C-reinforced 6061Al composites

Cu is an important microalloying element in Al-Mg-Si (6xxx series) alloys, but its role in B4C-reinforced Al-Mg-Si composites is rarely known. In this work, using the state-of-the-art Cs-corrected transmission electron microscopy (TEM), the Cu-related precipitation in a B4C/6061 Al composite fabricated at different temperatures is revealed at an atomic level. In the composite hot-pressed at 560 °C, Q phase is the main Cu-contained precipitates. When the pressing temperature increases to 620 °C, the chemical reactions between B4C reinforcements and the alloy matrix generate Al3BC and MgB2. Moreover, Cu is found to segregate at the interfaces between precipitates and the matrix, which is assumed to increase the nucleation of the reaction products.