Hierarchical strain distribution analysis formed in DP steel using a combination of metallographic image and digital image correlation method
Hierarchical strain distribution analysis formed in DP steel using a combination of metallographic image and digital image correlation method
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结合金相图像和数字图像相关方法对 DP 钢进行分层应变分布分析
DOI：
10.2355/tetsutohagane.100.1238
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发表时间：
2014
影响因子：
0.3
通讯作者：
S. Takaki
中科院分区：
文献类型：
--
作者：
Nobuo Nakada;M. Nishiyama;N. Koga;T. Tsuchiyama;S. Takaki
和导致韧性断裂的宏观应变集中，将数字图像相关（DIC）方法应用于通过扫描电子显微镜（SEM）获得的数字图像，以分析低碳双相钢中多尺度的应变分布。除了晶界，马氏体晶粒中的亚结构和铁素体基体中的腐蚀阴影在SEM图像中被清楚地观察到，它们增强了SEM数字图像的随机性。因此，SEM图像和DIC方法的组合（SEM-DIC方法）能够在多个尺度上评估金属中的不均匀应变分布。应变分布的发展看起来不同的放大倍数的SEM观察，由于像素依赖的空间分辨率的差异;微观尺度的应变图表明，应变是本地化的铁素体基体，而宏观尺度的应变图显示，应变似乎存在于拉伸试样的宽度。这一结果表明，宏观应变集中是伴随着渗透的微观局部应变。回火处理降低了马氏体的硬度，使马氏体晶粒内的应变显著增加，导致铁素体与马氏体之间的应变差减小。因此，不仅微观局部应变的发展，而且宏观应变集中的延迟，导致DP钢的塑性显着恢复。
and the macroscopic strain concentration responsible for ductile fracture, digital image correlation (DIC) method was applied to the digital images obtained by a scanning electron microscope (SEM) to analyze a strain distribution in a low carbon dual-phase steel in multiple scales. As well as grain boundaries, a substructure in martensite grains and a corrosion shade in ferrite matrix were clearly observed in SEM image and they enhance the random nature of SEM digital image. Therefore, the combination of SEM image and DIC method (SEM-DIC method) is able to evaluate a heterogeneous strain distribution in metal in multiple scales. The development of strain distribution looks different depending on the magnification of SEM observation due to the difference in pixel-dependent spatial resolution; micro-scale strain map indicated that strain is localized in ferrite matrix, while macro-scale strain map revealed that strain seems to exist over a width of tensile specimen. This result suggests that macroscopic strain concentration is accompanied by a percolation of microscopic localized strains. In addition, the strain in martensite grains is increased considerably as the hardness of martensite is reduced by tempering treatment, which leads to the reduction in the strain gap between ferrite and martensite. As a result, the developments of not only microscopic localized strain but also macroscopic strain concentration are retarded, leading to the significant recover of ductility in DP steel.