This paper presents a study on damage evolution for inhomogeneous structure consisting of acicular ferrite (AF) and granular bainite (GB) in advanced steel. The characteristics of crystal orientation were also analyzed. Firstly, the reliability of the deformed image obtained by repositioning for digital image correlation (DIC) calculation was evaluated using the zero-deformation experiments and 95% confidence interval length. Obtained results show that the influence of rigid body displacement induced by repositioning on the credibility can be ignored, and the accuracy and robustness meet the experimental requirements in this study. Then, tensile tests were carried out in rolling direction (RD) and transverse direction (TD). In RD tensile, the local damage mainly expands continuously inside the adjacent bands. The transmission of strain in the AF area has a significant turn at the GB boundary. Results of TD show that the damage extends along the coarse GB grain boundaries, which is the main reason for the occurrence of microcracks. Moreover, the crystal orientation also displays banded morphology. As the load increases, the fields of AF exhibit the most of increased KAM values at higher stress. The larger size of GB and its single orientation weaken the ability to resist crack propagation. This work helps to fully understand the negative effects of coarse GB morphology on mechanical properties and reveal the damage mechanism.

本文介绍了高级钢中由针状铁素体 (AF) 和粒状贝氏体 (GB) 组成的不均匀组织的损伤演化研究。还分析了晶体取向的特征。首先，使用零变形实验和 95% 置信区间长度评估通过重新定位进行数字图像相关 (DIC) 计算获得的变形图像的可靠性。得到的结果表明，重新定位引起的刚体位移对可信度的影响可以忽略不计，精度和鲁棒性满足本研究的实验要求。然后，在轧制方向（RD）和横向（TD）上进行拉伸试验。在 RD 拉伸中，局部损伤主要在相邻带内连续扩展。AF 区域的应变传递在 GB 边界处有明显的转变。TD 结果表明，损伤沿粗 GB 晶界延伸，这是微裂纹发生的主要原因。此外，晶体取向也显示带状形态。随着载荷的增加，AF 场在较高应力下表现出大部分增加的 KAM 值。GB 的较大尺寸及其单一取向削弱了抵抗裂纹扩展的能力。这项工作有助于充分理解粗GB形态对机械性能的负面影响并揭示损伤机制。晶体取向也显示带状形态。随着载荷的增加，AF 场在较高应力下表现出大部分增加的 KAM 值。GB的较大尺寸及其单一取向削弱了抵抗裂纹扩展的能力。这项工作有助于充分理解粗GB形态对机械性能的负面影响并揭示损伤机制。晶体取向也显示带状形态。随着载荷的增加，AF 场在较高应力下表现出大部分增加的 KAM 值。GB 的较大尺寸及其单一取向削弱了抵抗裂纹扩展的能力。这项工作有助于充分理解粗GB形态对机械性能的负面影响并揭示损伤机制。