In the current study, the microstructure evolution and mechanical behaviour in a commercial low silicon boron steel were investigated after one-step quenching and partitioning (Q&P) treatment under different isothermal temperatures in the range 260–320 °C. This processing approach resulted in a complex microstructure consisting of a tempered martensite matrix with bainitic ferrite, fresh martensite, and retained austenite, offering a superior combination of mechanical properties compared to the directly water-quenched condition, where a fully martensitic structure was exhibited. The Q&P processed steel isothermally held at a high temperature of 320 °C showed lower work-hardening, which was mainly associated with the lower fraction of initially formed martensite and the corresponding tempering responses, compared to the steels held at lower temperatures. The phase transformation behaviour throughout the heat treatment was studied by dilatometry, regarding the martensitic transformation upon initial cooling, carbon partitioning combined with the martensite tempering and austenite decomposition during isothermal holding, as well as the fresh martensite formation on the final cooling. Additionally, the microstructure characteristics were examined using X-ray diffraction, scanning electron microscope, and electron backscatter diffraction techniques.

在当前的研究中，在260-320°C的不同等温温度下，通过一步淬火和分配（Q＆P）处理后，研究了商用低硅硼钢的显微组织演变和力学行为。这种加工方法导致了复杂的微观结构，该组织由回火的马氏体基体与贝氏体铁素体，新鲜的马氏体和残留奥氏体组成，与直接水淬条件下表现出完全的马氏体结构相比，具有优异的机械性能组合。经过Q＆P处理的钢在320°C的高温下等温保持，其加工硬化率较低，这主要与初始形成的马氏体的分数较低以及相应的回火响应有关，与保持在较低温度下的钢相比。通过膨胀法研究了整个热处理过程中的相变行为，包括初始冷却时的马氏体相变，等温保温过程中碳分配与马氏体回火和奥氏体分解相结合以及最终冷却时新的马氏体形成。另外，使用X射线衍射，扫描电子显微镜和电子背散射衍射技术检查了微观结构特征。以及最终冷却时形成的新鲜马氏体。另外，使用X射线衍射，扫描电子显微镜和电子背散射衍射技术检查了微观结构特征。以及最终冷却时形成的新鲜马氏体。另外，使用X射线衍射，扫描电子显微镜和电子背散射衍射技术检查了微观结构特征。