两相区轧制后淬火引入马氏体降低钢板屈强比

晶粒细化和分裂增韧可使两相区轧制的层状超细晶钢板具有高强度同时韧性优异.前期研究发现轧后空冷生成的层状超细晶钢板，存在屈强比偏高的问题，高达0.9.本研究通过轧后淬火在层状超细晶组织中引入马氏体的方法降低屈强比.研究发现，在750℃和810℃轧制后淬火，层状超细晶组织中可生成体积分数约为14%的马氏体.此部分马氏体使拉伸过程中呈现连续屈服行为，提高加工硬化率，使钢板的屈强比降至0.7以下，解决了屈强比偏高的问题.此外，实验钢在具有高强度的同时，韧性优良.

Introducing Martensite to Reduce Yield Ratio of Steel Plates Rolled in Dual-Phase Region by Quenching

Grain refinement and delamination toughening can endow high strength and superior toughness to laminated and ultrafine-grained steel plates rolled in the dual-phase region. The previous study indicated that the laminated and ultrafine-grained steel plates possessed a high yield ratio up to 0.9 when air cooling was applied after rolling. In the present study， martensite was introduced to the laminated and ultrafine-grained steel plates by quenching after rolling to reduce the yield ratio. We found that martensite with a volume fraction of ~14% was generated by quenching followed by rolling at 750℃ or 810℃. Continuous yielding behavior was present during tensile testing due to the existence of martensite， and high work hardening rate was obtained. As expected， the reduced yield ratio lower than 0.7 was realized so that the problem that yield ratio was too high was solved for the laminated and ultrafine-grained steel plates. Moreover， high strength and good toughness were acquired.