Zhu Chen, Cerezo Alfred, Smith George D W
Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH, UK.
Ultramicroscopy. 2009 Apr;109(5):545-52. doi: 10.1016/j.ultramic.2008.12.007. Epub 2008 Dec 24.
The nature of the initial carbides formed during the early stages of the tempering of steels is still a matter of debate. Conventionally, the main transition carbide is described as epsilon carbide, with a composition of approximately Fe(2.4)C. However, earlier one-dimensional atom probe (1DAP) results indicated the existence of carbon-rich regions having much lower carbon contents, with maxima of around 10at%. There was some uncertainty about the interpretation of the 1DAP results, because of possible problems with alignment of the aperture and with trajectory aberration effects. We have therefore re-visited this topic, using the three-dimensional (3D) atom probe, and studying both a model Fe-Ni-C alloy and a well-known engineering steel (AISI4340). We demonstrate that, for both materials, low-temperature (20-150 degrees C) aging produces carbon-rich regions with average peak carbon contents of up to 10%. We show for the first time the three-dimensional structure of these carbon-rich regions, and demonstrate that fine-scale faulting exists within them.
钢回火早期形成的初始碳化物的性质仍然存在争议。传统上，主要的过渡碳化物被描述为ε碳化物，其成分约为Fe(2.4)C。然而，早期的一维原子探针（1DAP）结果表明存在碳含量低得多的富碳区域，其最大值约为10at%。由于孔径对准和轨迹像差效应可能存在问题，对1DAP结果的解释存在一些不确定性。因此，我们使用三维（3D）原子探针重新研究了这个课题，并研究了一种模型Fe-Ni-C合金和一种著名的工程钢（AISI4340）。我们证明，对于这两种材料，低温（20-150摄氏度）时效会产生平均峰值碳含量高达10%的富碳区域。我们首次展示了这些富碳区域的三维结构，并证明其中存在精细尺度的位错。
