Microstructure evolution during reheating of a Nb-bearing steel Ⅱ. Dislocation-precipitate interaction  

作　　者：Meizhen Cheng Enlong Dong Huibin Wu Shanwu Yang Xinlai He Huaxing Hou 

机构地区：[1]Materials Science and Engineering School, University of Science and Technology Beijing, Beijing 100083 [2]Anshan Iron ＆ Steel Group Corporation, Anshan 114003, China

出　　处：《Journal of University of Science and Technology Beijing》2005年第4期321-325,共5页北京科技大学学报（英文版）

摘　　要：Cooled in water after the isothermal relaxation of deformed austenite for different times, a Nb-bearing microalloyed steel always exhibits the synthetic microstructure in which bainitic ferrite dominates. Strain-induced precipitates do not occur in an unrelaxed sample while they distribute outside dislocations in the sample relaxed for long time. Most of the strain induced precipitates distribute along dislocations in the sample relaxed for proper time. After bainitic transformation, the dislocations formed in the deformed austenite remain to be pinned by the precipitates so that the thermostability of the bainitic ferrite is improved. Coarsening of the precipitates accompanied by their distribution density change has caused the first hardness peak of bainite during reheating. The second hardness peak is attributed to the precipitates, which nucleate in bainite. Dislocations inside the laths getting rid of the pinning of precipitates and their polygonization play the precursor to the evolution of microstructures during reheating.Cooled in water after the isothermal relaxation of deformed austenite for different times, a Nb-bearing microalloyed steel always exhibits the synthetic microstructure in which bainitic ferrite dominates. Strain-induced precipitates do not occur in an unrelaxed sample while they distribute outside dislocations in the sample relaxed for long time. Most of the strain induced precipitates distribute along dislocations in the sample relaxed for proper time. After bainitic transformation, the dislocations formed in the deformed austenite remain to be pinned by the precipitates so that the thermostability of the bainitic ferrite is improved. Coarsening of the precipitates accompanied by their distribution density change has caused the first hardness peak of bainite during reheating. The second hardness peak is attributed to the precipitates, which nucleate in bainite. Dislocations inside the laths getting rid of the pinning of precipitates and their polygonization play the precursor to the evolution of microstructures during reheating.

关 键 词：dislocations strain induced precipitates PINNING microstructure evolution 

分 类 号：TG142[一般工业技术—材料科学与工程]