Anisotropic Growth of the Primary Dendrite Arms in a Single-Crystal Thin-Walled Nickel-Based Superalloy,Advanced Engineering Materials

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Anisotropic Growth of the Primary Dendrite Arms in a Single-Crystal Thin-Walled Nickel-Based Superalloy
Advanced Engineering Materials ( IF 3.4 ) Pub Date : 2022-01-19 , DOI: 10.1002/adem.202101332
Selina Körber ₁ , Michael Fleck ₁ , Rainer Völkl ₁ , Uwe Glatzel ₁

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The influence of the withdrawal rate and wall thickness on the primary and secondary dendrite arm spacings of single-crystal specimens manufactured by the Bridgman process is investigated. Thin-walled specimens with wall thicknesses of 0.4, 0.8, 1, and 2 mm are compared with conventional cast single-crystal cylindrical specimens with a diameter of 15 mm of the nickel-based superalloy MAR M247LC. It is found that the average primary dendrite arm spacing decreases slightly with decreasing wall thickness, whereas the secondary dendrite arm spacing is relatively independent of the cast wall thickness. The slight decrease in primary dendrite arm spacing relates to an ≈ 0.2 mm wide boundary zone next to the ceramic mold/cast metal interface that is not only present in the thin-walled specimens, but also within cylindrical single-crystal specimens. Within this boundary zone, the primary dendrite arm spacing is anisotropic. While the spacing of two dendritic cores sitting aside each other (y-direction) remains at the bulk value, the spacing of two dendritic cores sitting in line with the interface normal (x-direction) is significantly reduced.

中文翻译：

单晶薄壁镍基高温合金中一次枝晶臂的各向异性生长

研究了拉拔率和壁厚对 Bridgman 工艺制造的单晶试样一次和二次枝晶臂间距的影响。将壁厚为 0.4、0.8、1 和 2 mm 的薄壁试样与直径为 15 mm 的镍基高温合金 MAR M247LC 的常规铸造单晶圆柱形试样进行了比较。发现平均一次枝晶臂间距随着壁厚的减小而略有减小，而二次枝晶臂间距与铸件壁厚相对无关。一次枝晶臂间距的轻微减小与靠近陶瓷模具/铸造金属界面的 ≈ 0.2 mm 宽的边界区域有关，该边界区域不仅存在于薄壁样品中，还存在于圆柱形单晶样品中。在这个边界区域内，一次枝晶臂间距是各向异性的。而两个彼此并排的树突核的间距（y方向）保持在体积值，与界面法线（x方向）对齐的两个枝晶核的间距显着减小。

更新日期：2022-01-19

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