Mesoscopic nature of serration behavior in high-Mn austenitic steel
Mesoscopic nature of serration behavior in high-Mn austenitic steel
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DOI：
10.1016/j.actamat.2020.116543
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发表时间：
2020-12
期刊：
影响因子：
9.4
通讯作者：
S. Hwang;Myeong-heom Park;Y. Bai;A. Shibata;W. Mao;H. Adachi;Masugu Sato;N. Tsuji
中科院分区：
文献类型：
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作者：
S. Hwang;Myeong-heom Park;Y. Bai;A. Shibata;W. Mao;H. Adachi;Masugu Sato;N. Tsuji
我们彻底阐明了高锰奥氏体钢锯齿行为的介观本质，这与其特有的局域变形有关。采用了一种典型的面心立方(FCC)单相结构的高锰钢Fe-22Mn-0.6C(wt.%)。经过4次反复冷轧和退火热处理，获得了平均晶粒度为2.0μm的完全再结晶组织。在初始应变速率为8.3×10−4s−1的条件下进行了室温拉伸试验，并用数字图像相关技术分析了局部应变和应变率的分布。结果表明，以变形局部化带的形成、扩展和湮灭为特征的一种独特的应变局部化行为，即所谓的Portevin-Le Chatelier(PLC)带，决定了整体力学响应在应力-应变曲线上表现为锯齿状。此外，还利用拉伸试验过程中的同步加速器X射线衍射仪来了解材料中与PLC条带有关的情况。当所有PLC带通过梁的位置时，(200)面近垂直于拉伸方向的晶格应变下降，这表明PLC带内部发生了应力松弛。同时，当PLC带通过束流位置时，位错密度急剧增加，说明材料主要在PLC带内发生塑性变形和加工硬化。所有结果一致地解释了介观尺度上的锯齿行为。应力-应变曲线上的锯齿行为完全对应于22Mn-0.6C钢中PLC带的形成、扩展和消失，局域变形即PLC带控制了材料的特征应变硬化。
We have thoroughly clarified the mesoscopic nature of serration behavior in a high-Mn austenitic steel in connection with its characteristic localized deformation. A typical high-Mn steel, Fe-22Mn-0.6C (wt. %), with a face centered cubic (FCC) single-phase structure was used in the present study. After 4 cycles of repeated cold-rolling and annealing process, a specimen with a fully recrystallized microstructure having a mean grain size of 2.0 μm was obtained. The specimen was tensile tested at room temperature at an initial strain rate of 8.3 × 10−4s−1, during which the digital image correlation (DIC) technique was applied for analyzing local strain and strain-rate distributions in the specimen. Obtained results indicated that a unique strain localization behavior characterized by the formation, propagation and annihilation of deformation localized bands, so-called Portevin–Le Chatelier (PLC) bands, determined the global mechanical response appearing as serration on the stress-strain curve. In addition, thein-situsynchrotron XRD diffraction during the tensile test was utilized to understand what was happening in the material with respect to the PLC banding. Lattice strain of (200) plane nearly perpendicular to the tensile direction dropped when every PLC band passed through the beam position, which indicated a stress relaxation occurred inside the PLC band. At the same time, the dislocation density increased drastically when the PLC band passed the beam position, which described that the material was plastically deformed and work-hardened mostly within the PLC band. All the results obtained consistently explained the serration behavior in a mesoscopic scale. The serration behavior on the stress-strain curve totally corresponded to the formation, propagation and annihilation of the PLC band in the 22Mn-0.6C steel, and the localized deformation, i.e., the PLC banding, governed the characteristic strain hardening of the material.