Relaxation of Deformed Austenite and Refinement of Bainite in a Nb-Containing Microalloyed Steel

作     者：Shanwu Yang, Xuemin Wang, Chengjia Shang, Xinlai He, Yi Yuan Material Science and Engineering School, University of Science and Technology Beijing, Beijing 100083, China 

作者机构：Univ Sci & Technol Beijing Sch Mat Sci & Engn Beijing 100083 Peoples R China 

出 版 物：《Journal of University of Science and Technology Beijing》 (北京科技大学学报（英文版）)

年 卷 期：2001年第8卷第3期

页      面：214-217页

核心收录：

学科分类：08[工学] 080502[工学-材料学] 0805[工学-材料科学与工程（可授工学、理学学位）] 

主　　题：stress relaxation strain induced precipitation refinement 

摘      要：By means of stress relaxation and strain-induced precipitation in deformed austenite, bainite with micron sheaves size was obtained in Nb-containing steel. Microstructures of deformed samples isothermally relaxed for various time followed by cooling in water were examined. Stress relaxation test and transmission electron microscopy (TEM) were employed to detect precipitation of microalloy elements, such as Nb, Ti, during isothermal holding after deformation. All the samples were constituted by lath-like bainite along with acicular ferrite, but the size of bainitic sheaves and the amount of acicular ferrite were changed with relaxation time. To achieve optimum refinement, relaxation should be confined in the stage when the precipitates have sufficiently grown and started to coarsen. The sample having not undergone relaxation does not exhibit obvious refinement despite of its higher dislocation density. These results indicate that relaxation promotes bainite to refine, which is because deformed austenitic grains are divided by dislocation walls formed during relaxation and acicular ferrite formed before bainitic transformation.