Substructure and crystallography of lath martensite in as-quenched interstitial-free steel and low-carbon steel
Substructure and crystallography of lath martensite in as-quenched interstitial-free steel and low-carbon steel
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淬火无间隙原子钢和低碳钢板条马氏体的亚结构和晶体学
DOI：
10.1016/j.actamat.2023.118675
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发表时间：
2023
期刊：
影响因子：
9.4
通讯作者：
Tsuzaki Kaneaki
中科院分区：
文献类型：
--
作者：
Shibata Akinobu;Miyamoto Goro;Morito Shigekazu;Nakamura Akiko;Moronaga Taku;Kitano Houichi;Gutierrez-Urrutia Ivan;Hara Toru;Tsuzaki Kaneaki
用聚焦离子束扫描电子显微镜连续切片和先进的透射电子显微镜研究了无间隙位(IF)钢和低碳钢(0.2C钢)淬火板条马氏体的亚结构和结晶学特征。三维分析表明，所谓的板条是最小的结构单元，其形态表现为楔形板，而不是理想的板条形状。IF钢的习惯面取向分布在(5 7 5)ATO(1 1 1)Ai上，而在0 2 C钢中则接近根据马氏体晶学唯象理论所预测的结果。在IF钢中，可以观察到较发达的位错胞、缠绕位错和弯曲位错。相反，在0.2C钢中观察到了直位错和渗碳体的形成。此外，两种钢在给定板条内的取向都发生了显著变化。板条边界包括规则间隔的台阶和(0 1 1)个Matomistic梯田平面。与(0 1 1)M晶面不连续相对应的界面位错可以分步观察到，这些位错的引入是为了补偿相邻板条之间的取向偏差。此外，在0.2C钢的板条和块状晶界观察到碳的偏析。对位错结构、渗碳体的形成以及碳原子在板条和块状晶界上的偏析的观察结果表明，淬火过程中亚结构发生了显著变化。根据我们的实验结果，我们讨论了板条马氏体亚结构和结晶学特征的来源。
In this study, the substructures and crystallographic features of as-quenched lath martensite in interstitial-free (IF) steel and low-carbon steel (0.2C steel) were investigated using focused ion beam-scanning electron microscopy serial sectioning and advanced transmission electron microscopy. A three-dimensional analysis revealed that the morphology of the so-called lath, the smallest structural unit, exhibited a wedge-shaped plate instead of the ideal lath shape. The habit plane orientations were distributed from (5 7 5)Ato (1 1 1)Ain the IF steel, whereas they were near to that predicted based on the phenomenological theory of martensite crystallography in the 0.2C steel. In the IF steel, well-developed dislocation cells, tangled dislocations, and curved dislocations could be observed. Conversely, straight dislocations and cementite formation were observed in the 0.2C steel. Moreover, the orientation changed significantly inside a given lath in both steels. The lath boundary comprised regularly spaced steps with (0 1 1)Matomistic terrace planes. Interfacial dislocations corresponding to the discontinuity of the (0 1 1)Mlattice planes could be observed at steps, and these dislocations were introduced to compensate for the misorientation between adjacent laths. Additionally, carbon segregations were observed at the lath and block boundaries in the 0.2C steel. Our observation results on the dislocation structures, cementite formation, and segregation of carbon atoms on the lath and block boundaries indicated that the substructure changed significantly during quenching. Based on our experimental results, we discuss the origin of the substructures and crystallographic features of lath martensite.