Ben Haj Slama Meriem, Gey Nathalie, Germain Lionel, Zhu Kangying, Allain Sébastien
Institut Jean Lamour UMR Université de Lorraine, CNRS 7198 Nancy, France.
Laboratoire d'Etude des Microstructures et de Mécanique des Matériaux (LEM3), UMR, Université de Lorraine, F-57000 Metz, France.
Materials (Basel). 2018 Sep 24;11(10):1808. doi: 10.3390/ma11101808.
The stability of lath-like microstructures during low-temperature isothermal ageing was analyzed in a Fe5Ni0.33C (in wt %) steel. The microstructures were characterized using Scanning Electron Microscopy (SEM) coupled with Electron Backscatter Diffraction (EBSD). Advanced orientation data processing was applied to quantify the hierarchical and multiscale organization of crystallographic variants subdividing Prior Austenite Grains (PAG) into packets/blocks/sub-blocks. The result shows that ferrite laths of martensite or lower bainite are stable, whatever the ageing temperature (up to 380 °C). On the contrary, a granularization process is triggered when microstructures contain a fraction of upper bainite. This metallurgical evolution corresponds to a rapid and significant change of the ferrite matrix involving a disappearance of 60° disoriented blocks. The phenomenon affects in turn the mechanical properties. The final microstructures obtained after isothermal holding look like granular bainite, which raises some questions about the classification of bainite.
在Fe5Ni0.33C（重量百分比）钢中分析了板条状微观组织在低温等温时效过程中的稳定性。使用扫描电子显微镜（SEM）结合电子背散射衍射（EBSD）对微观组织进行表征。应用先进的取向数据处理来量化将原始奥氏体晶粒（PAG）细分为包/块/子块的晶体学变体的层次和多尺度组织。结果表明，马氏体或下贝氏体的铁素体板条是稳定的，无论时效温度如何（高达380°C）。相反，当微观组织包含一部分上贝氏体时，会引发粒化过程。这种冶金演变对应于铁素体基体的快速且显著变化，涉及60°取向差块的消失。该现象进而影响力学性能。等温保持后获得的最终微观组织看起来像粒状贝氏体，这对贝氏体的分类提出了一些问题。
