The Al–33% wt. Cu and Al–33% wt. Cu/5% wt. C composites are prepared using mechanical alloying (MA) of elemental powders followed by cold and hot pressing. The features of phase transformations in the obtained in this way powder samples and composites are studied using X-ray diffraction analysis and scanning electron microscopy. The MA during 1–2 hours leads to an intensification of the reaction processes and dissolution of copper in aluminium with the formation of a supersaturated solid solution of Al (Cu) containing up to 4.9 at.% and 1.3 at.% copper in powders Al–33% wt. Cu and Al–33% wt. Cu/5% wt. C, respectively. Further MA results in formation of metastable b.c.c. Al$_4$Cu$_9$ and stable b.c.t. Al$_2$Cu phases. Thus, the phase composition of both powder mixtures after 8 hours of milling includes 3 crystalline phases: Al(Cu), Al$_4$Cu$_9$ and Al$_2$Cu. As also shown, the addition of 5% wt. of graphite during MA promotes both fracturing of metal powders and wrapping of graphite particles around them. The crystalline structure of the graphite is shown to transform into amorphous one during MA. Hot pressing leads to the decomposition of metastable Al$_4$Cu$_9$ in all composites, as well as the formation of Al$_4$C$_3$ carbide in Al–Cu/C composites. The effect both phase composition (the presence of metastable Al$_4$Cu$_9$ and stable Al$_2$Cu phases, as well as Al$_3$C$_4$ carbide) and microstructure modification of MAed powders on the mechanical properties of composites after cold and hot pressing is considered. Possible strengthening mechanisms of Al–Cu and Al–Cu/C composites are discussed.