为揭示稀土元素对高温合金凝固行为及铸态组织的影响，促进稀土改性变形高温合金的研制，本工作以一种含高质量分数γ′相镍基变形高温合金，即GH4151合金为研究对象，调整稀土元素La的添加量，通过对未添加La元素以及不同La含量的合金铸态组织和均匀化组织进行观察，分析了La含量（0、0.01、0.1、1（wt.%质量百分比，下同））对铸态以及均匀化态合金的枝晶形貌、偏析情况、析出相特征的影响规律。结果发现，La含量从0.01 wt.%La增加到0.1 wt.%La后，GH4151合金的一次枝晶间距和二次枝晶间距逐渐减小，当La含量增加至1 wt.%，一次枝晶间距呈增加趋势。在0.1 wt.%La合金中发现存在富La析出相，且伴随O、S等元素的富集。添加La元素可显著影响合金中(γ+γ′)共晶、Laves相、MC碳化物η相在枝晶间的析出，降低GH4151合金中Ti、Nb元素在枝晶间的偏析程度。0.01 wt.%La合金(γ+γ′)共晶明显减少，η相比例增加，随La含量提高，(γ+γ′)共晶逐渐增加，MC碳化物和η相减少。通过调控微量元素La可明显降低相同均匀化条件处理后Ti、Nb、Mo的残余偏析指数，从而提高合金的均质性。

The high alloying degree of GH4151 alloy gives rise to severe elemental segregation. Rare earth elements (REEs) have a great influence on the as-cast microstructure. In the present study, we delved into the evolution of the both the as-cast and homogenized microstructures of GH4151 alloy, modulating the content of the REE lanthanum (La) at varying concentrations (0, 0.01, 0.1, 1 wt.%, respectively). The results demonstrated that the inclusion of 0.01 wt.% La into GH4151 alloy led to a notable reduction in both primary and secondary dendrite spacings. Furthermore, in the 0.1 wt.% La alloy, a precipitate phase comprising La, O, and S was distinctly identified. Notably, the introduction of La significantly impacted the precipitation behavior of key phases such as (γ+γ′) eutectic, Laves phase, MC carbide, and η phase within the interdendritic regions, concomitantly mitigating the degree of segregation of Ti and Nb elements. Specifically, the (γ+γ′) eutectic content was conspicuously diminished in the 0.01 wt.% La alloy, whereas the proportion of η phase was increased. As the La content increased, the (γ+γ′) eutectic content gradually augmented, while the abundances of MC carbide and η phase diminished. Crucially, the modulation of trace La content facilitated a substantial reduction in the residual segregation indices of Ti, Nb, and Mo post homogenization, thereby enhancing the homogeneity of these major segregation elements. This improvement underscores the potential of REEs, particularly La, in refining the microstructure and mitigating segregation in GH4151 alloy.