The as-cast microstructure of a single-crystal CMSX-4 Ni-base superalloy produced by directional solidification was studied. The 〈100〉 misorientation of the angled and spiral grain selectors was evaluated for 3.33 and 5.0 mm/min withdrawal rates. The dendritic microstructure presented primary dendrite arm spacing around 370 µm (for a withdrawal rate of 3.33 mm/min) and 320 µm (for 5.0 mm/min); and interdendritic γ–γ′ islands, whose volume fraction was around 5.4% (for 3.33 mm/min) and 6.1% (for 5.0 mm/min). The microsegregation profiles of one withdrawal condition (for 5.0 mm/min) were used to extrapolate the solidus and γ′ solvus temperatures using the Thermo-Calc software. These microsegregation profiles of the as-cast microstructure also affected the solid-state γ′ precipitation in terms of shape, size and volume fraction. In the center of the dendrite, the γ′ precipitates were regularly cubic-shaped with a face of approximately 0.5 µm and a volume fraction of 55%. In the periphery of the dendrite, the morphology of the γ′ precipitates was more asymmetric, and the volume fraction of the γ′ phase increased to 65%. Two morphologies of the interdendritic γ–γ′ islands, fine and coarse, were observed, and a eutectic solidification sequence was proposed. The results indicated that the chemical composition of the interdendritic liquid progressed from hypoeutectic (fine interdendritic structure) to hypereutectic (coarse interdendritic structure) during the solidification.

研究了定向凝固法制备的单晶CMSX-4 Ni基高温合金的铸态组织。评估了成角度的和螺旋状晶粒选择器的<100>取向不良，其退刀速度为3.33和5.0 mm / min。树枝状组织的主要枝晶臂间距大约为370 µm（退出速率为3.33 mm / min）和320 µm（最长为5.0 mm / min）。和树突状的γ - γ '岛，其体积分数分别为5.4％（3.33毫米/分钟）和6.1％（5.0毫米/分钟）。使用一种退避条件（5.0 mm / min）的微偏析图来推断固相线和γ使用Thermo-Calc软件的固溶温度。铸态微观结构的这些微偏析轮廓也影响了固态γ '沉淀的形状，大小和体积分数。在枝晶的中央，γ '沉淀物呈规则的立方体形状，其表面约为0.5μm，体积分数为55％。在枝晶的外围，γ '沉淀的形态更加不对称，并且γ '相的体积分数增加到65％。树突间γ – γ的两种形态观察到细小和粗糙的岛，并提出了共晶凝固顺序。结果表明，在凝固过程中，枝晶间液体的化学成分从亚共晶（精细的枝晶结构）发展到过共晶（粗枝晶结构）。