Three-dimensional maps of geometrically necessary dislocation densities in additively manufactured Ni-based superalloy IN718
Three-dimensional maps of geometrically necessary dislocation densities in additively manufactured Ni-based superalloy IN718
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DOI：
10.1016/j.ijplas.2020.102709
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发表时间：
2020-08
影响因子：
9.8
通讯作者：
Wyatt A. Witzen;A. Polonsky;T. Pollock;I. Beyerlein
中科院分区：
文献类型：
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作者：
Wyatt A. Witzen;A. Polonsky;T. Pollock;I. Beyerlein
在这项工作中，我们提出了一种表征几何必要位错（GNDs）的亚颗粒三维分布的方法，并将其应用于增材制造（AM）镍基高温合金IN718。利用TriBeam层析成像技术获得三维电子后向散射衍射（EBSD）数据集，三维分辨率为1.5μmin。我们证明该方法提供了亚颗粒GND分布的三维评估。对于所研究的各种AM晶粒，GNDs排列成长而非结晶的亚边界，位于晶粒内部并沿着构建方向和穿过晶粒内部延伸。研究了GNDs计算中三维邻域的选择，发现子边界足够清晰，只考虑最近的邻域就足够了。子边界内的总GND密度高，可达1013m−2以上，而远离子边界的总GND密度低，约为1011m−2或以下。结果表明：GNDs以边向GNDs为主（占总GNDs密度的57%），且在{111}型平面上分布不均匀，在（111）型平面上累积最少；这些发现表明，AM颗粒含有致密的GND亚边界，这将显著影响其力学性能。
In this work, we present a method to characterize the subgranular three-dimensional distribution of geometrically necessary dislocations (GNDs) and apply it to an additively manufactured (AM) Ni-based superalloy IN718. A three-dimensional (3D) Electron Backscatter Diffraction (EBSD) data set was obtained using TriBeam tomography with resolutions of 1.5μmin all three dimensions. We demonstrate that the method provides a 3D assessment of the subgranular GND distribution. For the various AM grains studied, the GNDs were arranged into long non-crystallographic subboundaries, lying within the interior of the grain and extending along the build direction and through the grain interior. The choice of 3D neighborhood in the calculation of GNDs is examined, finding that the subboundaries are sufficiently sharp such that considering only the nearest neighbors is sufficient. The total GND densities in the subboundaries are high, reaching in excess of 1013m−2, whereas away from the subboundaries they are low, at around 1011m−2or below. The analysis reveals that GNDs are predominantly edge-oriented GNDs (>57%of total GND density) and are unequally distributed among the {111}-type planes, accumulating the least on the (111) plane. These findings reveal that AM grains contain well-organized patterns of dense GND subboundaries that would noticeably affect their mechanical performance.