【摘要】 研究目的：厚钢板在大型桥梁工程中的应用越来越多，其厚度方向的力学性能梯度特征对构件承载能力存在影响，目前厚钢板中表层-芯部屈服行为差异的形成机制尚不明确。本文研究以Q420qD桥梁厚钢板为对象，通过分层拉伸试验结合多尺度显微组织表征，揭示其厚度方向屈服行为差异的微观机理。研究结论：（1）试验钢板表层呈现连续屈服特性，而芯部各层表现出不连续屈服行为；（2）显微组织分析显示，全厚度组织均由粒状贝氏体（GB）和多边形铁素体（PF）构成；由表层到芯部，平均晶粒尺寸从6.86μm增大至11.57μm；位错密度在表层至1/8厚度范围内出现显著下降；（3）机理分析揭示了厚钢板厚度方向屈服行为差异的位错-晶粒尺寸分布协同作用机制；（4）本研究成果可为厚钢板的生产工艺优化提供理论依据，并为大型桥梁工程中厚钢板的合理应用提供参考。更多还原

【Abstract】 Research purposes: Thick steel plates are essential structural components in grand bridges, where through-thickness mechanical property gradients critically influence overall performance. The mechanisms underlying the distinct yield behaviors between surface and core regions in thick steel plates remain insufficiently understood. This study investigates a Q420 qD grade bridge steel plate and employs layered tensile tests combined with multi-scale microstructural characterization to elucidate the micro-mechanisms underlying through-thickness variations in yielding behavior.Research conclusions:(1) The surface layer of the experimental steel plate exhibits continuous yielding behavior, while the core layers demonstrate pronounced discontinuous yielding characteristics.(2) Microstructural analysis shows that the full-thickness structure is composed of granular bainite(GB) and polygonal ferrite(PF). From the surface to the core, the average grain size increases from 6.86 μm to 11.57 μm. Dislocation density shows a marked decrease from surface to 1/8 thickness before stabilizing.(3) The mechanistic analysis reveals a dislocation-grain size distribution synergistic mechanism underlying the yield behavior differences.(4) These results offer a theoretical foundation for the process optimization of thick steel plates and provide a reference for their appropriate application in grand bridge engineering.更多还原