Revealing complex planar defects and their interactions at atomic resolution in a Laves phase containing Co-base superalloy
Revealing complex planar defects and their interactions at atomic resolution in a Laves phase containing Co-base superalloy
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DOI：
10.1016/j.actamat.2023.119568
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发表时间：
2023-12
期刊：
影响因子：
9.4
通讯作者：
Li Wang;Yihao Wang;F. Pyczak;M. Oehring;Min Song;Yong Liu
中科院分区：
文献类型：
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作者：
Li Wang;Yihao Wang;F. Pyczak;M. Oehring;Min Song;Yong Liu
本研究发现，Co-9Al-9W-2Zr合金在900℃退火后形成的立方zrco_2基Laves相中广泛形成了不同的平面断层和大量的断层相交，并在原子分辨率上进行了检测。通过分析，证实了同步剪切是三次Laves相中孪晶、外源层错和内禀层错形成的机制，有三个等效的Burgers向量1/6<112> Shockley部分可用于同步剪切。但位错核心区的原子洗牌也需要适应完美晶格和缺陷晶格中的原子排列。首次观测到以缺失单个共原子层和恒定间隙宽度为特征的新型平面断层。缺失的单层被认为是由平面上的空位偏析引起的，特别是在{111}孪晶平面上。间隙下方的原子以不同的洗牌向量洗牌到新的位置，形成不同类型的平面断层。热处理试样中的大多数交叉点是相当温和的。入射平面断层偶尔会穿过阻隔平面断层，W在交汇区域富集。在更复杂的交集中，同步剪切和原子变换发生在外在和内在层错以及孪晶中，空位扩散和原子变换发生在新型平面断层中，形成观察到的交集构型。平面断层的广泛形成可能会显著改变含Laves相材料的力学行为，并影响其功能性能。
In this study, extensive formation of different planar faults and substantial fault intersections were found and examined at atomic resolution in the cubic ZrCo2based Laves phase formed in a Co-9Al-9W-2Zr alloy after annealing at 900 ºC. By analysis, it is confirmed that synchro-shear is the mechanism to form twins, extrinsic stacking faults and intrinsic stacking faults in the cubic Laves phase with three equivalent Burgers vectors 1/6<112> Shockley partials available for synchro-shear. But atomic shuffling in the dislocation core region is also required to fit the atomic arrangement in perfect and faulted lattices. Novel types of planar faults featured by a missing single Co-atom layer and a constant gap width are for the first time observed. The missing single layer is believed to be induced by the vacancy segregation on planes, especially on {111} twinning planes. The atoms below the gap shuffle into their new positions with different shuffling vectors to form different types of planar faults. Most intersections in the heat-treated specimen are quite gentle. Only occasionally, incident planar faults pass the barrier planar faults, and W is enriched in the intersection regions. In cases of more complex intersections, synchro-shear and atomic shuffling occur in extrinsic and intrinsic stacking faults as well as in twins, and vacancy diffusion and atom shuffling occur in the novel types of planar faults to form the observed intersection configurations. The extensive formation of planar faults might significantly alter the mechanical behavior and also influence functional properties of Laves phase containing materials.