The fracture surfaces and cracks in technically pure iron, Fe-2.5% Si alloy and low-carbon steel grade S235JR produced by quasi-cleavage (QC) hydrogen-assisted cracking (HAC) as well as by true cleavage (TC) were studied and compared on different scales through the quantitative and qualitative fractographic and side surface examinations. The mixed type QC/TC fracture surfaces were obtained using two-step mechanical testing methods involving the tension of the through-notched specimens under in-situ hydrogen charging followed by rapid fracture in liquid nitrogen. The side surface and fractographic examinations, including the quantitative facets analysis, were conducted using scanning electron microscopy (SEM), confocal laser scanning microscopy (CLSM) and electron-backscattering diffraction (EBSD) technique. It is established, that the QC and TC fracture surfaces demonstrate fundamentally different morphological and topological features in all materials investigated. It is found that, depending on the material, the average angle of misorientation (AM) between the QC facets is 1.5–2 times lower than that of the TC facets. Thus, it is concluded that the crystallographic orientation of QC facets is generally different from TC. Owing to this feature, the path of the QC HAC through the microstructure of all investigated materials is featured by the remarkably lower spatial out-of-plane deviation on the scale equal to or larger than a few facets. Conversely, on the scale of an individual facet, the path of QC HAC deviates to a greater extent than that of the TC crack. This fundamental difference between QC HAC and TC cracking is found to be not significantly influenced by the chemical composition of the ferritic alloys.

研究了通过准解理 (QC) 氢辅助开裂 (HAC) 和真解理 (TC) 生产的工业纯铁、Fe-2.5% Si 合金和低碳钢级 S235JR 的断口和裂纹，并通过定量和定性断口和侧面检查在不同尺度上进行比较。使用两步机械测试方法获得混合型 QC/TC 断裂表面，包括在原位充氢下通过缺口试样的张力，然后在液氮中快速断裂。使用扫描电子显微镜 (SEM)、共聚焦激光扫描显微镜 (CLSM) 和电子背散射衍射 (EBSD) 技术进行侧面和断口检查，包括定量面分析。它成立，QC 和 TC 断裂表面在所有研究的材料中表现出根本不同的形态和拓扑特征。发现，根据材料的不同，QC 小平面之间的平均错向角 (AM) 比 TC 小平面低 1.5-2 倍。因此，可以得出结论，QC 面的晶体取向通常与 TC 不同。由于这一特征，QC HAC 通过所有研究材料的微观结构的路径的特点是在等于或大于几个方面的尺度上显着较低的空间面外偏差。相反，在单个面的尺度上，QC HAC 的路径比 TC 裂纹的路径偏差更大。