以真空感应熔炼+电渣重熔+真空自耗重熔三联冶炼GH4065高合金化镍基变形高温合金棒材(直径280 mm)为对象，系统研究了该合金点状偏析的低倍组织、元素分布、第二相及晶粒形貌，分析了典型溶质元素对点状偏析行为的影响，探讨点状偏析的形成规律与机制及控制思路。结果表明，GH4065合金点状偏析主要源于枝晶间富Ti、Nb等元素的熔体密度较小冲破枝晶臂流动形成的通道偏析；锻造后生成较多的板条状η相、块状M₃B₂型硼化物与MC型碳化物。热力学相计算亦证实了点状偏析区较正常组织区域更容易生成η相、M₃B₂和MC。热处理后，与正常组织区域相比，点状偏析中仍存在板条状η相，一次γ′相的尺寸和数量明显增加，二次γ′相尺寸和形貌基本相同但数量减少。分析发现，由于点状偏析区的成分变化使得γ′相回溶温度升高，导致锻造中粗大γ′相阻碍再结晶长大，点状偏析区晶粒尺寸小于正常组织区域。采取前道次冶炼精细化控制、释放电极残余应力、适度降低真空自耗重熔熔化速率、加强真空自耗重熔冷却等措施，可以有效降低点状偏析的形成倾向。

GH4065 alloy is a new type of high-alloyed wrought superalloy, in which freckle defect is extremely prone to form in large ingot. In the present research, the freckle of GH4065 alloy bar with the diameter of 280 mm produced by vacuum induction melting (VIM)+electroslag remelting (ESR)+vacuum arc remelting (VAR) triple smelting was studied. The macrostructure, secondary phases and grain structure of the freckle were investigated, the influences of solute elements on the freckle were analyzed, and both the mechanism and control methods were also discussed. The results show that the freckle in GH4065 alloy is caused by channel segregation with the low-density Ti and Nb-rich melt flows. Additionally, lots of lath-like η-phases, block M₃B₂ borides and MC carbides are formed in the forged condition. It is confirmed by the thermodynamic calculations that the η-phases, M₃B₂ borides and MC carbides are much easier forming in the freckle than that in matrix. After heat treatment, compared with matrix, the lathy η-phases are still existed in the freckle; the size and quantity of primary γ′ phases increase significantly while the size and morphology of the secondary γ′ phase are basically identical, only with less quantity. It has been found that due to the high content of γ′ phase, the γ′ dissolution temperature in the freckle is higher than that in the matrix. This induces an impeded recrystallization process caused by the coarsened γ′ phases during forging process and the grain size of the freckle region is significantly smaller than that of matrix. Based on this study, the formation of freckle can be effectively controlled by meticulous controlling of the previous smelting process, releasing of electrode residual stress, suitably reducing VAR melting rate, and accelerating VAR cooling.