低合金高强钢板沿厚度方向优异的组织均匀性是良好强韧性的重要保证，理解贝/马复相的回火反应有助于调整低合金高强钢板的热处理工艺参数，实现超厚结构板的变形控制。本工作以贝/马复相的回火硬度和微观组织演变行为作为研究重点，并与单一马氏体和下贝氏体的回火行为进行了对比。结果表明，等温淬火贝/马复相的硬度与下贝氏体含量呈线性关系。短时间回火过程中，单一马氏体回火硬度最高，其次为贝/马复相，单一下贝氏体回火硬度最低，这与长时间回火硬度正好相反。短时间回火过程中，碳化物的粗化与回火硬度的降低息息相关，其中贝/马复相中马氏体和下贝氏体碳化物的粗化速率与单一马氏体和下贝氏体碳化物粗化速率分别保持一致；长时间回火过程中，贝/马复相板条和碳化物的粗化与单一下贝氏体更为相似。

Variations in lower bainite and martensite phase configurations through thickness play an important role in achieving an optimum combination of strength and toughness for thick high-strength low-alloy (HSLA) steel plates. A comprehensive understanding of the hardness and microstructural evolution of tempered lower bainite and martensite (LB/M) mixtures contributes to the adjustment of the quenching and tempering parameters to further control HSLA plate deformation during manufacturing. Therefore, this study focused on the tempering behavior of the mixed LB/M microstructure and compared this behavior with those of the singular martensite and lower bainite phases. Results have shown that the hardness of LB/M microstructures follows the rule of mixtures. Hardness declines from singular martensite to the LB/M microstructure and further decreases to singular lower bainite during short-term tempering, whereas an opposite hardness decreasing trend is observed during long-term tempering. Carbide coarsening leads to a decrease in hardness during short-term tempering, where the coarsening of martensitic and lower bainitic carbides in the LB/M microstructure is consistent with that of singular martensitic and bainitic carbides. Furthermore, the coarsening of laths and carbides in the LB/M mixture is similar to that in the singular lower bainitic microstructure for long-term tempering, where lower bainitic carbides are more stable than martensitic carbides.