Abstract The inhomogeneous microstructures caused by mesosegregation deeply influence the mechanical properties and stability of materials. However, the relationship between tensile deformation and inhomogeneous microstructures has received limited attention. This paper reports an in-depth investigation of the tensile deformation behavior and strain distribution of mesosegregated high-strength low-alloy (HSLA) steel. A multi-scale digital image correlation (DIC) analysis of in-situ scanning electron microscopy images reveals that the discrepancies in the tensile deformation behavior are caused by the microstructural discrepancies between the positive segregation zones (PSZs) and negative segregation zones (NSZs). The larger number of crossed-slip bands in the NSZs indicates a more serious plastic deformation caused by the softer microstructures of this zone, i.e., tempered upper bainite and allotriomorphic ferrite. On the contrary, the harder microstructures of the PSZs, i.e., bulk bainite ferrite, tempered martensite, and lower bainite, having fewer crossed-slip bands, display a higher plastic deformation resistance. Additionally, the lower plastic deformation resistance in the NSZs leads to a lower failure threshold and causes a fracture in the NSZs. This work reveals the influence of mesosegregation on deformation behavior and provides the guideline on the post-heat treatment of heavy forgings.

中文翻译：

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中偏析高强低合金钢的原位变形表征

摘要 介偏析引起的微观结构不均匀严重影响材料的力学性能和稳定性。然而，拉伸变形与不均匀微观结构之间的关系受到的关注有限。本文报告了对中间偏析高强度低合金 (HSLA) 钢的拉伸变形行为和应变分布的深入研究。原位扫描电子显微镜图像的多尺度数字图像相关 (DIC) 分析表明，拉伸变形行为的差异是由正偏析区 (PSZ) 和负偏析区 (NSZ) 之间的微观结构差异引起的。NSZs 中交叉滑移带的数量越多，表明该区域较软的显微组织，即回火上贝氏体和同素异形铁素体引起的塑性变形越严重。相反，PSZ 的较硬的显微组织，即块状贝氏体铁素体、回火马氏体和下贝氏体，具有较少的交叉滑移带，显示出较高的塑性变形抗力。此外，NSZ 中较低的塑性变形抗力导致较低的失效阈值并导致 NSZ 断裂。这项工作揭示了中间偏析对变形行为的影响，并为重型锻件的后热处理提供了指导。回火马氏体和下贝氏体具有较少的交叉滑移带，显示出较高的塑性变形抗力。此外，NSZ 中较低的塑性变形抗力导致较低的失效阈值并导致 NSZ 断裂。这项工作揭示了中间偏析对变形行为的影响，并为重型锻件的后热处理提供了指导。回火马氏体和下贝氏体具有较少的交叉滑移带，显示出较高的塑性变形抗力。此外，NSZ 中较低的塑性变形抗力导致较低的失效阈值并导致 NSZ 断裂。这项工作揭示了中间偏析对变形行为的影响，并为重型锻件的后热处理提供了指导。