Deitz Julia I, Ruggles Timothy J, Noell Philip J, Susan Donald F, Kustas Andrew B, Kotula Paul G, Michael Joseph R
Materials Characterization and Performance Department, Sandia National Laboratories, 1515 Eubank Blvd. SE - Mail Stop 1411 - Albuquerque, NM 87123, USA.
Microsc Microanal. 2023 Jun 9;29(3):913-918. doi: 10.1093/micmic/ozad041.
Heat-treated FeCo-based magnetic alloys were characterized using a suite of electron microscopy techniques to gain insight into their structural properties. Electron channeling contrast imaging (ECCI) in the scanning electron microscope (SEM) found unique grains towards the outer edge of a FeCo sample with nonuniform background contrast. High-magnification ECCI imaging of these nonuniform grains revealed a weblike network of defects that were not observed in standard uniform background contrast grains. High-resolution electron backscattered diffraction (HR-EBSD) confirmed these defect structures to be dislocation networks and additionally found subgrain boundaries within the nonuniform contrast grains. The defect content within these grains suggests that they are unrecrystallized grains, and ECCI can be used as a rapid method to quantify unrecrystallized grains. To demonstrate the insight that can be garnered via ECCI on these unique grains, the sample was imaged before and after micro indentation. This experiment showed that slip bands propagate throughout the material until interacting with the dislocation networks, suggesting that these specific defects provide a barrier to plastic deformation. Taken together, these results show how ECCI can be used to better understand failure mechanisms in alloys and provides further evidence that dislocation networks play a critical role in the brittle failure of FeCo alloys.
采用一系列电子显微镜技术对经过热处理的铁钴基磁性合金进行表征，以深入了解其结构特性。扫描电子显微镜（SEM）中的电子通道对比度成像（ECCI）发现，在铁钴样品的外边缘存在独特的晶粒，其背景对比度不均匀。对这些不均匀晶粒进行高倍ECCI成像，发现了一个网状的缺陷网络，而在标准均匀背景对比度的晶粒中未观察到这种网络。高分辨率电子背散射衍射（HR-EBSD）证实这些缺陷结构为位错网络，并且在对比度不均匀的晶粒中还发现了亚晶界。这些晶粒中的缺陷含量表明它们是未再结晶晶粒，并且ECCI可以用作量化未再结晶晶粒的快速方法。为了证明通过ECCI可以获得关于这些独特晶粒的见解，在微压痕前后对样品进行了成像。该实验表明，滑移带在整个材料中传播，直到与位错网络相互作用，这表明这些特定缺陷对塑性变形形成了障碍。综上所述，这些结果展示了ECCI如何用于更好地理解合金中的失效机制，并进一步证明位错网络在铁钴合金的脆性失效中起关键作用。
