Enhancing the Strength of Aluminum-Boron Carbide Composites to a High Degree by Magnesium Addition for Use in Automotive Applications

We report here a significant enhancement of the hardness of aluminumboron carbide composites by the addition of magnesium. Reactive sintering between boron carbide and aluminum-magnesium occurs by the application of heat and pressure and during subsequent annealing at high-homologous temperatures of the matrix. In this case, the deformation-induced plastic yielding enables the incorporation and dispersion of hard particles in aluminum-matrix. We examine the decomposition behavior of boron carbide at high-homologous temperatures in contact with magnesium and aluminum, and observe the interfacial, aluminum-magnesium-boride, AlMgB4 , and aluminum-boro-carbide, Al3BC, phases at boron carbide/matrix interfaces as revealed by the high-resolution transmission electron microscopy. We demonstrate that the hardness of these composites has been enhanced by two to five folds as compared to the base alloy and the existing aluminum-boron carbide composites. The addition of magnesium improves interfacial cohesion significantly between the matrix and ceramic particles as a result of interfacial boride phase, and primarily contributes to the enhancement of strength. This provides a novel method of developing aluminum-based high strength composites. 

Keywords: Aluminum alloys, Boron carbide and transmission electron microscopy, Interfaces, Microstructure, Metal matrix composites.