A comparative study has been carried out on the microstructural evolution, mechanical properties, wear behaviour, as well as the aging kinetics of the Al-4.5 (wt. percent) Cu alloy and TiB2 or TiC particles reinforced in situ composite, subjected to rolling at temperatures in the mushy zone. The preparation of Al-4.5Cu-5 (wt. percent) TiB2 and Al-4.5Cu-5TiC composites involved the in situ formation of the TiB2 or TiC particles inside the molten α-Al through a mixed salt route, followed by stir casting into plates. The microstructures of the as cast alloy have shown coarse α-Al dendrites, while those of the as cast composite possess rosette-type grains with TiB2 or TiC particles located at the grain boundaries. The plate-shaped specimens, in cast or pre-hot rolled conditions, have been rolled at the temperatures for nominal liquid volume fractions of 10, 20 or 30 percent, to thickness reductions in the range of 2.5-10 percent. The temperatures corresponding to the selected volume fractions have been obtained from the Al-Cu binary equilibrium phase diagram. The liquid volume fractions have been experimentally determined using image analysis of the globules of dendrites or fine grain clusters formed due to the rapid solidification of liquid in samples quenched after soaking at the selected phase diagram temperature, and found close to the desired nominal volume fractions of liquid. While the alloy could be rolled free of defects under all conditions, the as cast Al-4.5Cu-5TiB2 composites have failed through alligatoring, except when thickness reduction was 5 percent or lower at 30 volume percent liquid. Strain localization and shear failure have been proposed as the mechanisms of failure by alligatoring, which was partially prevented on prior hot rolling, causing homogenization and equiaxed grain formation. Alligatoring could not be observed on mushy state rolling of the Al-4.5Cu-5TiC composites, except for 10 percent thickness reduction. Mushy state rolling leads to nearly equiaxed grain structure having bimodal size distributions. Remarkable grain refinement takes place in matrix of the as-cast Al 4.5Cu-5TiB2 composite, on subjecting to multiple mushy state roll passes. Significant redistribution of the TiB2 particles is also achieved after seven mushy state roll passes, as those are driven from their original locations at grain boundaries by viscous drag of the intergranular liquid, subjected to shear during rolling. But subjecting the in situ Al 4.5Cu-5TiC composite to multiple mushy state roll passes leads to failure with intergranular cracking due to the formation of brittle Al3Ti and Al4C3 through a chemical reaction at the αAl-TiC interfaces, during soaking or rolling at temperatures in the mushy zone.