Abstract <p>This study examines the effect of TiB₂ contents (4wt%, 8wt%, and 12 wt%) and hot rolling strain (50% and 75%) on microstructural evolution and mechanical performance of in-situ Al-4.5Cu/TiB₂ composites. The composites were synthesized using stir casting assisted by the mixed salt reaction and followed by hot rolling at 450&#xa0;°C. In-situ developed TiB₂ particle were uniformly distributed throughout the composite, and grain refinement was achieved due to combined effect of TiB₂ reinforcement and hot rolling. Highest recrystallized grain fraction (31.4%) in the composite was achieved at 8% TiB₂ at 50% rolling reduction, with recrystallization diminishing at higher strain levels. At 8% of TiB_2, the composite exhibited an increase of 23% in UTS and 50% increase in microhardness compared to base alloy. Hot rolling at 75% reduction results improvement of UTS by 38% compared to as-cast composite resulting in an overall enhancement of 71% over the base alloy. Microhardness also improved by 20% compared to as-cast composite with an overall increase of 81% compared to the base alloy. These findings highlight the synergistic effect of TiB₂ content and hot rolling in tailoring the microstructure and mechanical behavior of in-situ synthesized Al-4.5Cu/TiB₂ composites.</p> Graphical Abstract <p></p>