Local Phase Transformation Strengthening at Microtwin Boundaries in Nickel-Based Superalloys
Local Phase Transformation Strengthening at Microtwin Boundaries in Nickel-Based Superalloys
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DOI：
10.1016/j.actamat.2022.118206
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发表时间：
2022-08-06
期刊：
影响因子：
9.4
通讯作者：
Mills, M. J.
中科院分区：
文献类型：
--
作者：
Egan, A. J.;Xue, F.;Mills, M. J.
这项工作研究了两个类似的多晶合金，不同的只有1原子%的Nb含量，阐明其在高温蠕变过程中的局部相变强化的效果。压缩蠕变试验进行了750？和600 MPa至0.5%的应变，导致以微孪晶为主的变形。高Nb合金RRHT5在最小蠕变速率方面表现出比RRHT3更好的上级蠕变强度。通过原子分辨率扫描透射电子显微镜和能量色散谱，以及原子探针断层扫描，揭示了一种新的局部相变沿着微孪晶界面的RRHT 5的变形显微组织的特征。取向特定的cECCI和超晶格本征和非本征层错在该合金的分析去卷积其他局部相变的强化效果。密度泛函理论计算补充了实验结果，并建议这是chi相的形成。RRHT 5蠕变强度的增加归因于沿微孪晶界面的沿着局部相变，这抑制了微孪晶的有害增厚和应变的快速积累。(c)2022 Acta Materialia Inc.由爱思唯尔有限公司出版。保留所有权利。
This work investigated two similar polycrystalline alloys, differing by only 1 at% Nb content, which elucidated its effect on local phase transformation strengthening during high temperature creep. Compression creep tests were conducted at 750 ? and 600 MPa to 0.5% strain, resulting in deformation dominated by microtwinning. Higher Nb alloy RRHT5 exhibited superior creep strength to RRHT3 in terms of minimum creep rate. The deformation microstructures were characterized via atomic resolution scanning transmission electron microscopy and energy-dispersive spectroscopy, as well as atom probe tomography, which revealed a novel local phase transformation along microtwin interfaces in RRHT5. Orientation specific cECCI and analysis of superlattice intrinsic and extrinsic stacking faults in this alloy deconvolved strengthening effects of other local phase transformations. Density functional theory calculations complemented the experimental results and suggested this was chi phase formation. Increased creep strength of RRHT5 was attributed to local phase transformation along microtwin interfaces, which inhibited deleterious thickening of microtwins and rapid strain accumulation. (c) 2022 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.