Al matrix composites with a high volume fraction of reinforcements were fabricated with a compact of Al-Ti-B4C powder mixtures by quick spontaneous infiltration (QSI) process in an aluminum melt. Given the exothermal nature of the reaction between CuO and Al, a certain amount of CuO addition to the Al-Ti-B4C system dramatically increases the adiabatic temperature and thereby enables the complete combustion reaction in an aluminum melt (about 1,173 K). After the QSI process, the compact fabricated with CuO retains its original shape and the obtained composite exhibits sound microstructure containing reaction products of TiB2, Al3BC and B4C. The formation of such reinforcements when adding CuO contributes to enhancing the properties of the composites that show far superior hardness and elastic modulus of 3.03 GPa and 158.9 GPa, respectively, with lower coefficient of thermal expansion (9.44 ppm-1) compared to those with no CuO addition.