Al-Si(-Cu)系耐热铸造合金组织调控策略的研究进展

Research progress of microstructural regulation strategies in Al-Si(-Cu) series heat-resistant casting alloys

摘要:

Al-Si(-Cu)系铸造合金兼具铸造性能、气密性和时效强化潜力，是发动机缸体、缸盖等热端复杂零部件的重要候选材料；但在300~350℃服役条件下，传统θ′、β′等亚稳强化相易粗化、溶解或相变，共晶Si和晶界组织也会退化，导致高温强度和蠕变抗力下降。本文在分析高温软化机制和研究瓶颈的基础上，系统梳理了近年来Al-Si(-Cu)系铸造合金的微观组织调控策略，重点归纳三类强化路径：低扩散过渡族/稀土元素构建热稳定纳米弥散相，相界面偏聚工程稳定θ′、Q′等亚稳析出相，以及晶间金属间化合物和共晶Si构成的刚性互联网络。在此基础上，讨论CALPHAD计算、机器学习、多尺度模拟和增材制造快速凝固技术在耐热组织设计中的作用。本文认为，Al-Si(-Cu)系耐热铸造合金的后续发展应从单一强化相设计转向兼顾高温强度、铸造工艺性、热裂敏感性和长期服役稳定性的多尺度协同调控。

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.