Effects of local stress, strain, and hydrogen content on hydrogen-related fracture behavior in low-carbon martensitic steel
Effects of local stress, strain, and hydrogen content on hydrogen-related fracture behavior in low-carbon martensitic steel
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DOI：
10.1016/j.actamat.2021.116828
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发表时间：
2021-04-07
期刊：
影响因子：
9.4
通讯作者：
Tsuji, Nobuhiro
中科院分区：
文献类型：
--
作者：
Shibata, Akinobu;Yonemura, Takashi;Tsuji, Nobuhiro
通过显微组织观察、有限元模拟和数字图像相关分析，研究了不同应力集中系数试样的氢相关断裂行为。所研究的合金是一种具有完全马氏体组织的简单模型合金（Fe-0.2C二元合金）。当含氢量较大（2.21质量ppm (ppm时为121质量ppm)）时，裂纹沿原有奥氏体晶界萌生扩展。通过有限元模拟发现，裂纹起裂部位对应于高应力和高氢含量区域。虽然应力集中因子不同，但裂纹起裂部位的应力水平和氢含量几乎相同，表明氢相关的晶间断裂起源于奥氏体晶界的应力控制脱黏。含氢量较小的试样（0.41质量ppm(22.5质量ppm)），准解理裂纹在缺口根部表面形成，沿{011}面扩展。有限元模拟结果表明，准解理裂纹起始部位的塑性应变最大。此外，通过DIC分析，我们证实了氢增强了局部塑性变形。由于准解理裂纹起裂部位的局部最大主应力、塑性应变和氢含量随应力集中系数的不同而不同，因此准解理裂纹起裂的临界定量条件并不像晶间裂纹起裂那样简单。(c) 2021 Acta Materialia Inc.Elsevier Ltd.出版。版权所有。
The present study investigated the hydrogen-related fracture behavior of specimens with different stress concentration factors through microstructure observation, finite element (FE) simulation, and digital image correlation (DIC) analysis. The alloy studied was a simple model alloy (Fe-0.2C binary alloy) with fully martensite structure. When the hydrogen content was large (2.21 mass ppm (121 at ppm)), the crack initiation and propagation occurred along the prior austenite grain boundaries. Through the FE simulations, we found that the crack initiation sites corresponded to the region with high stress and high hydrogen content. Although the stress concentration factors were different, the stress level and the hydrogen content at the crack initiation sites were almost the same, indicating that the hydrogen-related intergranular fracture originated from stress-controlled decohesion at the prior austenite grain boundaries. For the specimen with small hydrogen content (0.41 mass ppm (22.5 at ppm)), the quasi-cleavage cracks formed at the surface of the notch root and propagated along the {011} planes. The FE simulations revealed that the plastic strains were maximum at the initiation sites of the quasi-cleavage cracks. Moreover, we confirmed that hydrogen enhanced the local plastic deformation by DIC analysis. As the local values of maximum principal stress, plastic strain, and hydrogen content at the initiation sites of the quasi-cleavage cracks were different depending on the stress concentration factor, the critical quantitative condition for the initiation of quasi-cleavage cracking was not simple compared to that of the case of intergranular cracking.(c) 2021 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.