Hardening behavior and deformation microstructure beneath indentation in heavy ion irradiated 12Cr-ODS steel at elevated temperature
Hardening behavior and deformation microstructure beneath indentation in heavy ion irradiated 12Cr-ODS steel at elevated temperature
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DOI：
10.1016/j.jnucmat.2020.152606
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发表时间：
2021
影响因子：
3.1
通讯作者：
Huilong Yang;S. Kano;John McGrady;Jingjie Shen;Y. F. Li;Dongyue Chen;Kenta Murakami;H. Abe
中科院分区：
文献类型：
--
作者：
Huilong Yang;S. Kano;John McGrady;Jingjie Shen;Y. F. Li;Dongyue Chen;Kenta Murakami;H. Abe
采用纳米压痕试验、EBSD分析和TEM观察相结合的方法，研究了12 Cr-ODS钢在573 K下重离子辐照后压痕下显微组织的硬度行为和变形。首次研究了非辐照和辐照试样的纳米压痕硬度不均匀性，并与室温辐照试样进行了比较。随后，进行TEM观察，以了解在典型的低指数取向下测试的压痕下的变形行为。结果表明，在法向（ND）和轧制方向（RD）试样上均发生了明显的辐照硬化，且硬化效果随辐照剂量的增加而增强。同时，观察到各种各向异性的硬度行为，例如，与ND试样相比，RD试样的硬度值较低，硬化效果较弱，以及相对于[111]取向，[001]取向的硬度值较低，但硬化效果较大。此外，从573 K辐照的结果显示出类似的各向异性硬度行为从RT辐照得到的那些，尽管在573 K的辐照在该钢中表现出减弱的辐照硬化效应。TEM观察的压痕下的变形显微组织表明，（i）的变形影响区的深度随取向而变化，范围从约6-9倍的位错深度，和（ii）明显的位错晶界（GB）的压痕下的相互作用被证实表现出依赖于GB和压头压痕方向之间的几何关系。通过Schmid因子分析、压头与可能滑移面的几何相容性比较以及变形组织的TEM观察，讨论了硬度各向异性行为与显微组织特征之间的相关性。结果表明，12 Cr-ODS钢的各向异性硬度行为是由于晶粒取向和晶粒形貌的不均匀性共同作用的结果，在ND面存在低长径比的细长晶粒，在RD面存在纳米层状晶粒。
Hardness behavior and deformation of the microstructure beneath the indentation in 12Cr-ODS steel after exposure to heavy ion irradiation at 573 K were investigated with combined applications of nano-indentation tests, EBSD analysis, and TEM observation. The inhomogeneous nano-indentation hardness behavior was firstly investigated in both non-irradiated and irradiated specimens and compared to those at room temperature (RT) irradiation. Subsequently, TEM observations were performed to understand the deformation behaviors beneath the indentation tested at typical low-indexed orientations. Obvious irradiation hardening was confirmed in both the normal direction (ND) and rolling direction (RD) specimens, and the hardening effect intensified with an increase in irradiation dose. Meanwhile, various anisotropic hardness behaviors were observed such as a lower hardness value and a weaker hardening effect in the RD specimen compared to the ND specimen, and a lower hardness value but a greater hardening effect in [001] orientation relative to [111] orientation. Furthermore, results from 573 K irradiation showed similar anisotropic hardness behaviors with those obtained from RT irradiation, despite the fact that irradiation at 573 K exhibited a weakened irradiation hardening effect in this steel. TEM observation of the deformation microstructure beneath the indentation reveals that (i) the depth of the deformation affected zone varied with orientation, ranging from ~6-9 times that of the indent depth, and (ii) distinct dislocation-grain boundary (GB) interactions beneath the indentations was confirmed to exhibit dependence on the geometric relation between GB and indenter impression direction. Correlation between the anisotropic hardness behavior and microstructural features is discussed based on Schmid factor analysis, comparison of geometric favorability between indenter and possible slip planes, and TEM observation of deformation microstructure. The results conclude that the anisotropic hardness behaviors in the present 12Cr-ODS steel are ascribed to the combined effect of crystal orientation and the non-uniform grain morphology with the existence of the elongated grains having low aspect ratio in the ND plane and nano-layered grains in the RD plane.