Multi-stage micro-scale deformation-based processing of ultra-thin metallic sheets has been widely used in the manufacturing of light-weight parts with complicated structures. Because only a few grains are distributed along the thickness direction of ultra-thin sheets, the grain size effect on the in-grain microstructure evolution must be understood. Moreover, the intragranular orientation mismatch induced by prior processing needs to be studied to accurately describe the additional deformation resistance and anisotropy in the step-by-step fabrication. In this study, 0.1-mm-thick SS 316L sheet samples with different mean grain sizes were deformed to two strain levels, with the electron backscatter diffraction (EBSD) used to characterize the microstructures of the deformed samples. Based on the EBSD data and crystal plasticity finite element simulations, the effects of local constraints and grain size on intragranularly misoriented grain boundary (IMGB) evolution was statistically analyzed. The IMGB patterns were organized into four categories, and the characteristics of local constraints near the grain boundary triple junctions were delineated. The formation of IMGBs was found to be induced by the concentration of high local strain, which was governed by local constraints, including the geometrical and deformation-related factors. Because of the higher intragranular strain and longer dislocation moving distance before annihilation, the IMGBs accumulate more easily inside large grains. The collected local constraint characteristics and the linear correlation between IMGB length and grain area were applied in a proposed three-step procedure for estimating the IMGB patterns and magnitudes of the micro-scale deformation of ultra-thin sheets. This comprehensive and quantitative description of IMGB evolution provides a fundamental basis for understanding the grain-level deformation mechanisms and for the constitutive modelling of the mechanical responses of ultra-thin sheets in complex deformation.

基于多级微尺度变形的超薄金属片加工已广泛应用于制造结构复杂的轻质零件。由于只有少数晶粒沿超薄板的厚度方向分布，因此必须了解晶粒尺寸对晶内显微组织演变的影响。此外，需要研究由先前加工引起的晶内取向失配，以准确描述分步制造中的额外变形阻力和各向异性。在这项研究中，将具有不同平均晶粒尺寸的 0.1 毫米厚的 SS 316L 板材样品变形为两个应变水平，并使用电子背散射衍射 (EBSD) 来表征变形样品的微观结构。基于EBSD数据和晶体塑性有限元模拟，统计分析了局部约束和晶粒尺寸对晶内错向晶界（IMGB）演化的影响。将IMGB图案分为四类，并描绘了晶界三结附近的局部约束特征。发现 IMGBs 的形成是由高局部应变的集中引起的，该应变受局部约束的控制，包括几何和变形相关因素。由于湮没前较高的晶内应变和较长的位错移动距离，IMGBs更容易在大晶粒内聚集。将收集到的局部约束特征和 IMGB 长度与晶粒面积之间的线性相关性应用于所提出的三步程序中，用于估计 IMGB 模式和超薄板微尺度变形的大小。这种对 IMGB 演化的全面和定量描述为理解晶粒级变形机制和超薄板在复杂变形中的力学响应的本构建模提供了基础。