雀斑严重损害了高温合金叶片的晶体完整性和力学性能，给重型燃气轮机定向凝固大尺寸叶片的制备带来巨大挑战。本文回顾了国内外近几十年雀斑研究进展，包括通过原子探针、同步辐射、数值模拟等手段研究雀斑形成过程中的元素偏析、热溶质对流及枝晶碎臂行为，描述了基于温度场或糊状区密度的雀斑形成判据，阐释了叶片结构、工艺条件等对雀斑分布的影响规律，综述了雀斑缺陷的控制技术和方法。目前，关于雀斑的报道普遍聚焦于“小尺寸、拉速≤ 1.5 mm/min、高W/Re含量合金”的情形，这与工程实际中重型燃机“大叶片、拉速≥ 2.0 mm/min、低W/Re含量合金”时雀斑的凝固条件及发生状况存在较为显著的差异。因此，深入研发适用于重型燃机大尺寸叶片中雀斑的快速预测方法和有效控制技术，成为当前及未来的重要需求和研究方向。

Freckles severely degrade the crystalline integrity and high-temperature mechanical properties of superalloy blades, posing a critical barrier to the fabrication of large-sized directionally solidified blades for heavy-duty gas turbines. This paper reviews the research progress on freckles over the past several decades, both domestically and internationally. It summarizes investigations of elemental segregation, thermo-solutal convection, and dendrite arm fragmentation during freckle formation using techniques such as atom probe tomography, synchrotron radiation, and numerical simulation. Freckle formation criteria based on temperature fields or mushy-zone density have been described, and the influences of blade geometry and solidification parameters on freckle distribution have been elucidated. Moreover, freckle control techniques and methods are comprehensively reviewed. At present, most studies on freckles focus on cases involving “small-sized specimens, low withdrawal rates (≤ 1.5 mm/min), and alloys with high W/Re contents”, which exhibit relatively significant differences from the freckle solidification conditions and occurrence patterns of “large blades, high withdrawal rates (≥ 2.0 mm/min), and alloys with low W/Re content” in the engineering practice of heavy-duty gas turbines. Therefore, developing rapid freckle prediction methods and effective control technologies specifically suited to the solidification conditions of large blades in heavy-duty gas turbines has become a critical need and a key research direction for the present and future.