In this article, the influence of simulated thermal cycles for the heat-affected zone (HAZ) on the microstructural evolution and mechanical properties in a low-carbon high-strength Cu-bearing steel was investigated by microstructural characterization and mechanical tests. The results showed that the microstructure of the coarse-grained heat-affected zone (CGHAZ) and the fine-grained heat-affected zone (FGHAZ) was mainly comprised of lath martensite, and a mixed microstructure consisting of intercritical ferrite, tempered martensite and retained austenite occurred in the intercritically heat-affected zone (ICHAZ) and the subcritically heat-affected zone (SCHAZ). Also, 8–11% retained austenite and more or less Cu precipitates were observed in the simulated HAZs except for CGHAZ. Charpy impact test indicated that the optimum toughness was obtained in FGHAZ, which was not only associated with grain refinement, but also correlated with deformation-induced transformation of the retained austenite, variant configuration as interleaved type and a relatively weak variant selection. The toughness of ICHAZ and SCHAZ exhibited a slight downtrend due to the presence of Cu precipitates. The CGHAZ has the lowest toughness in the simulated HAZs, which was attributed to grain coarsening and heavy variant selection. In addition, the contribution of Cu precipitates to yield strength in simulated HAZs was estimated based on Russell–Brown model. It demonstrated an inverse variation trend to toughness.

在本文中，通过微观结构表征和力学测试，研究了模拟热循环对热影响区（HAZ）的影响，从而对低碳高强度含铜钢的微观组织演变和力学性能产生了影响。结果表明，粗晶粒热影响区（CGHAZ）和细晶粒热影响区（FGHAZ）的组织主要由板条马氏体组成，由临界铁素体，回火马氏体和残余马氏体组成的混合组织。奥氏体发生在临界热影响区（ICHAZ）和亚临界热影响区（SCHAZ）。另外，除了CGHAZ外，在模拟的热影响区中观察到8-11％的残留奥氏体，或多或少的Cu析出物。夏比冲击试验表明，在FGHAZ中获得了最佳的韧性，这不仅与晶粒细化有关，而且还与残余奥氏体的变形诱导相变，交错型组织和相对较弱的组织选择有关。由于存在铜沉淀，ICHAZ和SCHAZ的韧性显示出轻微的下降趋势。在模拟的热影响区中，CGHAZ的韧性最低，这归因于晶粒粗化和大量选择。此外，根据Russell-Brown模型估算了模拟热影响区中Cu析出物对屈服强度的贡献。它显示出韧性的逆变化趋势。而且还与残余奥氏体的变形引起的相变，相变配置为交错型以及相对较弱的相变选择相关。由于存在铜沉淀，ICHAZ和SCHAZ的韧性显示出轻微的下降趋势。在模拟的热影响区中，CGHAZ的韧性最低，这归因于晶粒粗化和大量选择。此外，根据Russell-Brown模型估算了模拟热影响区中Cu析出物对屈服强度的贡献。它显示出韧性的逆变化趋势。而且还与残余奥氏体的变形引起的相变，相变配置为交错型以及相对较弱的相变选择相关。由于存在铜沉淀，ICHAZ和SCHAZ的韧性显示出轻微的下降趋势。在模拟的热影响区中，CGHAZ的韧性最低，这归因于晶粒粗化和大量选择。此外，根据Russell-Brown模型估算了模拟热影响区中Cu析出物对屈服强度的贡献。它显示出韧性的逆变化趋势。这归因于晶粒粗化和大量的变种选择。此外，根据Russell-Brown模型估算了模拟热影响区中Cu析出物对屈服强度的贡献。它显示出韧性的逆变化趋势。这归因于晶粒粗化和大量的变种选择。此外，根据Russell-Brown模型估算了模拟热影响区中Cu析出物对屈服强度的贡献。它显示出韧性的逆变化趋势。