中文摘要：

对Q235级低碳钢板条马氏体在550℃多道次单向压缩变形后退火和室温大塑性变形轧制后在此温度退火的显微组织演变规律进行了对比研究，结合未变形板条马氏体在此温度的回火组织演变，讨论了变形对马氏体分解过程、铁素体再结晶晶粒尺寸和析出碳化物形貌的影响．实验结果表明，变形显著影响马氏体分解过程，促进渗碳体的析出和铁素体回复及再结晶．热变形组织铁素体再结晶晶粒尺寸在0．5μm左右；渗碳体形貌从细棒状向球状转变，随变形量增大渗碳体尺寸增大。继续保温60min导致铁素体晶粒长大到1μm左右，晶粒内部的渗碳体消失，原先在铁素体晶界析出的渗碳体球化、粗化．冷轧试样在550℃退火保温时间在30min内得到0．3～0．4μm超细晶粒和尺度小于150nm的弥散渗碳体颗粒组织；随退火保温时间延长到60min，铁素体再结晶晶粒长大到1．9um，渗碳体颗粒尺寸约160nm．

英文摘要：

The microstructure evolution during multi-pass warm deformation at 550 ℃ and subsequent annealing process of lath martensite was investigated and compared with that of SPD （severe plastic deformation） cold-rolled lath martensite during annealing at 550 ℃. In comparison with tempered martensite at the same temperature, the effects of warm and cold deformation on ferrite grain size and cementite precipitation were discussed. The results showed that both warm and cold deformation significantly promoted the precipitation of cementite as well as recovery and recrystallization of ferrite. The grain size of recrystallized ferrite after warm deformation was 0.5μm, meanwhile rod-type cementite particles changed to spherical-type, the size of cementite grew along with the increase of deformation reduction. Then ferrite grains grew up to 1μm when subsequently annealed at 550 ℃ for 60 min, and Ostwald ripening occurred during annealing process. In cold-rolled specimens which annealed at 550℃for 30 min, 0.3 - 0.4μm ferrite grains and dispersed cementite particles with the size below 150 nm formed. The mean sizes of ferrite grains and cementite particles grew up to 1.9 μm and 160 nm during subsequent annealing.