Abstract:Al-Si(-Cu) casting alloys are important candidate materials for complex hot-end components such as engine blocks and cylinder heads because they combine castability, gas tightness and precipitation-strengthening potential. Their use at 300~350°C, however, is limited by the coarsening, dissolution or transformation of metastable θ′ and β′ precipitates, together with degradation of eutectic Si and grain-boundary structures. This review summarizes recent progress in microstructural regulation strategies for improving the heat resistance of Al-Si(-Cu) casting alloys. Three routes are highlighted: thermally stable nanoscale dispersoids formed by low-diffusivity transition or rare-earth elements; interfacial segregation engineering to stabilize θ′, Q′ and other metastable precipitates; and rigid interconnected networks composed of grain-boundary intermetallic compounds and eutectic Si. The roles of CALPHAD calculations, machine learning, multiscale simulation and additive-manufacturing-assisted rapid solidification are also discussed. Overall, the development of heat-resistant Al-Si(-Cu) casting alloys is moving from single-phase strengthening toward multiscale cooperative regulation that balances high-temperature strength, casting adaptability, hot-tearing sensitivity and long-term service stability. This review provides guidance for composition design, heat-treatment optimization and microstructural evaluation of Al-Si(-Cu) alloys for engine hot-end applications.