The synergistic effects of pre-intercritical annealing treatments and multiple heating to the two-phase region (followed by quenching) on the microstructure and mechanical properties of dual-phase (DP) steel were studied. Intercritical annealing of ferritic-pearlitic, martensitic, and cold-rolled martensitic microstructures was investigated. The effects of tempering, austenitisation, grain growth, and recrystallisation were unravelled and an optimum holding time was characterised for each initial microstructure. Grain refinement by recrystallisation of cold-rolled martensitic microstructure resulted in the enhancement of tensile properties. Thermal cycling through multi-step intercritical annealing resulted in grain refinement and enhanced mechanical response. It was revealed that thermal cycling combined with the carefully controlled pre-intercritical microstructure could be simply used for the improvement of mechanical properties of DP steel.

中文翻译：

---

通过预临界退火处理和热循环改善双相钢的性能

研究了预临界退火处理和两相区多次加热（随后淬火）对双相 (DP) 钢组织和力学性能的协同作用。研究了铁素体-珠光体、马氏体和冷轧马氏体微观结构的临界间退火。揭示了回火、奥氏体化、晶粒生长和再结晶的影响，并对每个初始微观结构的最佳保温时间进行了表征。通过冷轧马氏体微观结构的再结晶来细化晶粒导致拉伸性能的增强。通过多步临界间退火的热循环导致晶粒细化和增强的机械响应。