Abstract: The Al-Fe alloy exhibits excellent thermal conductivity, which has broad application in electricity, automobiles, and electronic components industries. However, the coarse microstructure deteriorates the mechanical properties, development of new high-strength, high-thermal-conductivity alloys is essential. This study employed SEM, EPMA, in-situ synchrotron X-ray radiography, and synchrotron X-ray computed tomography to systematically examine the influence of Al-5Ti-1B (Al-Ti-B) addition and cooling rate on the microstructural characteristics, thermal conductivity, and mechanical properties of Al-Fe alloys. The findings demonstrate that introducing Al-Ti-B into Al-3Fe alloy generates TiB2 phases, acting as effective nucleation sites for iron-rich intermetallic phases (Fe-phases) and α-Al grains, significantly reducing the nucleation time. The primary Fe-phases and α-Al grains were significantly refined, thereby synergistically improving both the thermal conductivity and mechanical properties of the alloy. The aggregation of TiB2 suppresses the preferential growth of plate-like Fe-phase along the <010> orientation while promoting the formation of star-shaped Fe-phase that grow along multiple directions. In the Al-3Fe alloy with 0.3% Al-Ti-B addition under fast cooling, thermal conductivity peaks at 210 W/(m·K), a 14.5% increase over the base alloy. With 0.5% Al-Ti-B addition, the UTS, YS, and EL improve by 16.2%, 17.3%, and 54.3%, respectively. This study provides an efficient and convenient strategy for enhancing the thermal conductivity and mechanical performance of Al-Fe alloys.