A356.2 铝合金在航空航天及汽车轻量化领域应用广泛，但铸件性能的精准预测与调控仍是技术难点。 本研究在原有工艺基础上，通过优化原铝液加料策略和辅料(Ti 和 Si)的加入时序，提出新的改进方案，系统探究了冷却速率与稀土(RE)和锶(Sr)变质剂对 A356.2 铝合金凝固组织细化的协同影响。 通过扫描电子显微镜(SEM)和光学显微镜(OM)表征发现，冷却速率是组织细化的主导因素，水冷条件下的 α-Al 晶粒尺寸较自然冷却显著减小，且单独添加 RE可显著细化 α-Al 晶粒，并获得纤维状的共晶硅。 特别地，水冷条件下 RE 与 Sr 的交互作用由“协同”转为“拮抗”，试样的晶粒尺寸较单一、粗大，且共晶硅变质不完全。

A356.2 aluminium alloy is widely used in aerospace and automotive lightweight applications. However, accurateprediction and control of its casting performance remain technically challenging. In this study, an improved process wasdeveloped by optimizing the feeding strategy of molten aluminium and the addition sequence of auxiliary materials (Ti andSi). The synergistic effects of the cooling rate and rare earth (RE) and strontium (Sr) modifications on the refinement of thesolidification microstructure of A356.2 alloys were systematically investigated. Scanning electron microscopy (SEM) andoptical microscopy (OM) characterization reveal that the cooling rate is the dominant factor in microstructure refinement.The grain size of α-Al under water cooling is significantly smaller than that under natural cooling. The addition of REalone markedly refines α-Al grains and promotes the formation of fibrous eutectic silicon. Notably, the interaction betweenRE and Sr shifts from synergistic to antagonistic under water-cooling conditions, resulting in a coarser and more uniformgrain morphology with incomplete modification of eutectic silicon.