The carbon distribution behavior and crystal structure of as-quenched martensite in Fe-1Mn-C (C: 0.07 to 0.8 mass pct) steels were quantitatively investigated by atom probe tomography (APT) and X-ray diffraction with Rietveld analysis. APT revealed that the martensite steels contained quantities of carbon in solid solution far beyond its solubility in body-centered cubic (bcc)-Fe in all the alloys investigated; the carbon atoms were non-homogeneously distributed as carbides or aggregates on dislocations due to autotempering. Tetragonality was observed in the steels with interstitial solute carbon concentrations in the range of 0.1 to 0.7 mass pct, but was not evident below 0.1 mass pct. The appearance and disappearance of tetragonality in the low-carbon steels may be explained by the disordered bcc ↔ ordered body-centered tetragonal (bct) mechanism, considering the partial tetragonality due to the heterogeneity of the interstitial solute carbon distribution. The existence of tetragonality in the autotempered low-carbon steels can alternatively be understood by a mechanism based on the kinetic decrease of tetragonality during cooling, where the microscopic strain release is the rate-controlling process. The excess carbon solubility in the autotempered low- and medium-carbon martensite is due to the existence of tetragonal distortions, owing to the slow kinetics of the tetragonality decrease during cooling.

中文翻译：

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淬火后的Fe-1Mn-C（C：0.07至0.8 Mass Pct）马氏体中过量的溶质碳和四方性

通过原子探针层析成像（APT）和X射线衍射和Rietveld分析定量研究了Fe-1Mn-C（C：0.07至0.8质量pct）钢中淬火马氏体的碳分布行为和晶体结构。APT发现，在所有研究的合金中，马氏体钢中固溶体中的碳含量远远超过其在体心立方（bcc）-Fe中的溶解度。由于自回火，碳原子不均匀地分布为碳化物或聚集体。在间隙溶质碳浓度在0.1至0.7质量％的范围内的钢中观察到四方性，但在0.1质量％以下则不明显。考虑到由于间隙溶质碳分布的不均匀性而导致的部分四方性，低碳钢中四方性的出现和消失可以用无序的bcc↔有序体心四方（bct）机制来解释。可以通过基于冷却过程中四方性的动力学降低的机理来理解自回火低碳钢中四方性的存在，其中微观应变释放是速率控制过程。在自回火的低碳和中碳马氏体中过量的碳溶解性归因于四方形的存在，这是由于冷却过程中四方性下降的缓慢动力学所致。可以通过基于冷却过程中四方性的动力学降低的机理来理解自回火低碳钢中四方性的存在，其中微观应变释放是速率控制过程。在自回火的低碳和中碳马氏体中过量的碳溶解性归因于四方形的存在，这是由于冷却过程中四方性下降的缓慢动力学所致。可以通过基于冷却过程中四方性的动力学降低的机理来理解自回火低碳钢中四方性的存在，其中微观应变释放是速率控制过程。在自回火的低碳和中碳马氏体中过量的碳溶解性归因于四方形的存在，这是由于冷却过程中四方性下降的缓慢动力学所致。