Microscopic strain partitioning in Luders band of an ultrafine-grained medium Mn steel
Microscopic strain partitioning in Luders band of an ultrafine-grained medium Mn steel
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超细晶粒中锰钢 Luders 带中的微观应变分配
DOI：
10.1016/j.msea.2019.138050
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发表时间：
2019
期刊：
影响因子：
6.4
通讯作者：
M.X. Huang
中科院分区：
文献类型：
--
作者：
X.G. Wang;C.H. Liu;B.B. He;C. Jiang;M.X. Huang
本文研究了一种超细晶中锰相变诱发塑性(TRIP)钢在奥氏体-铁素体双相组织中Lüders带微观应变分配的测定和理解。首先，发展了一种微观数字图像相关(μ-DIC)方法，该方法能够在亚晶尺度上实现高分辨率的应变映射。由于当地的L应变评估，铁素体和残余奥氏体间的应变分配是定量的。结果表明，在宏观应变为9.5%时，铁素体中的平均Lüders应变约为10.1%，奥氏体中的平均Lüders应变约为9.1%，表明这两个相对Lüders带的塑性变形都很重要。除了两个相之间的应变分配外，一个更引人注目的发现是同一相内Lüders应变的显著异质性。结合应变场分析，用电子背散射衍射(EBSD)和透射电子显微镜(TEM)研究了应变分离的微观组织来源。结果表明，L带应变不均匀形成的主要原因是拉伸变形前初始组织中可动位错的不均匀分布。并证明了晶粒度和晶体织构是影响L应变分布的次要因素。
This paper is focused on the determination and understanding of the microscopic strain partitioning in the Lüders band of an ultrafine-grained medium Mn transformation-induced plasticity (TRIP) steel with austenite-ferrite dual phase microstructures. First, a microscopic digital image correlation (μ-DIC) method is developed that enables high-resolution strain mapping at the subgrain scale. Thanks to the local Lüders strain assessment, the strain partitioning between ferrite and retained austenite is quantified. It reveals that the average Lüders strain in ferrite is about 10.1% and that in austenite about 9.1% at a macroscopic Lüders strain 9.5%, thus it indicates that both phases are important to the plastic deformation in the Lüders band. Besides the strain partitioning between the two phases, a more striking finding is the significant heterogeneity of Lüders strain within the same phase. The microstructural origins for the strain partitioning are investigated using electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM) in combination with the strain field analysis. The results show that the main cause for strain heterogeneity formation in Lüders band can be attributed to the heterogenous distribution of mobile dislocations in the initial microstructure before tensile deformation. And the effects of grain size and crystallographic texture are proofed to be the secondary factors that may only have minor influence on Lüders strain distribution.