工程科学学报，第38卷，第3期：357-363,2016年3月 Chinese Journal of Engineering,Vol.38,No.3:357-363,March 2016 D0l:10.13374/j.issn2095-9389.2016.03.009:http://journals.ustb.edu.cn 热轧态与回火态AH80DB低碳贝氏体钢组织与冲击 韧性 赵雷超”，孙斌堂”，黄运华》，张施琦》，丁一”，闫小琴)，张跃” 1)北京科技大学材料科学与工程学院，北京1000832)北京科技大学新材料技术研究院，北京100083 3)长江大学机械工程学院，荆州434023 ☒通信作者，E-mail:xqyan(@mater.ustb.cdu.cn 摘要采用光学显微镜、扫描电子显微镜和透射电子显微镜对热轧态和回火态AH80DB低碳贝氏体钢的显微组织、马氏 体/奥氏体(M/A)岛、第二相的析出行为以及晶界取向差、有效晶粒尺寸进行研究，揭示回火后低碳贝氏体钢冲击韧性得到改 善的原因.结果表明：两种试样的组织均由板条状贝氏体、粒状贝氏体和针状铁素体组成，其中回火态试样中针状铁素体组 织较多.热轧态钢中存在较大尺寸M/A岛且呈方向性分布，大角度晶界比例占17.33%，有效晶粒尺寸为3.57um;而回火态 钢中M/A岛的尺寸较小，大角度晶界比例增加3.43%，有效晶粒尺寸减小0.56μm.热轧态钢中析出相主要是(Nb,T)C,尺 寸在50~150nm之间，回火态试样中析出较多细小的球状(Nb,Ti)C析出相，尺寸在10nm左右. 关键词低碳钢：贝氏体：冲击韧性；显微组织：析出相 分类号TG142.2 Microstructure and impact toughness of hot rolled and tempered low carbon bainitic steel AH80DB ZHAO Lei--ehao”,SUN Bin-tang”',HUANG Yun-hua,ZHANG Shi-g》,DlNG,YAN Xiao-gin回，ZHANG Yue” 1)School of Materials Science and Engineering,University of Science and Technology Beijing,Beijing 100083,China 2)Institute for Advanced Materials and Technology,University of Science and Technology Beijing,Beijing 100083,China 3)College of Mechanical Engineering,Yangtze University,Jingzhou 434023,China Corresponding author,E-mail:xqyan@mater.ustb.edu.cn ABSTRACT The microstructure,martensite/austenite (M/A)islands,precipitated phases,high-angle grain boundaries and effec- tive grain size of hot rolled and tempered low carbon bainitic steel AH80DB were studied by scanning electron microscopy (SEM), transmission electron microscopy (TEM)and electron back-scattered diffraction (EBSD).The reason for the improvement in impact toughness of the low carbon bainitic steel after tempering was discovered.The results show that the microstructures of both the samples mainly consist of lath bainite,granular bainite and acicular ferrite.There is more acicular ferrite in the tempered steel.Coarse M/A islands are found in the hot rolled steel and its distribution is directional,the ratio of large-angle grain boundaries is 17.33%,and the average effective grain size is 3.57 um.Nevertheless,the size of M/A islands decreases after tempering.Besides,the ratio of large- angle grain boundaries increases by 3.43%and the average effective grain size decreases by 0.56 um after tempering.The precipita- ted phase of the hot rolled steel is (Nb,Ti)C with the size of 50-150 nm,while much small and spherical precipitates with the size of about 10 nm appear after tempering. KEY WORDS low carbon steel:bainite:impact toughness:microstructure;precipitation 收稿日期：201501-23 基金项目：教育部创新团队和新世纪人才计划资助项目(RT1106):高等学校学科创新引智计划资助项目(B140O3):中央高校基本科研业务 费资助项目(FRF-As-3001A)工程科学学报，第 38 卷，第 3 期: 357--363，2016 年 3 月 Chinese Journal of Engineering，Vol． 38，No． 3: 357--363，March 2016 DOI: 10． 13374 /j． issn2095--9389． 2016． 03． 009; http: / /journals． ustb． edu． cn 热轧态与回火态 AH80DB 低碳贝氏体钢组织与冲击 韧性 赵雷超1) ，孙斌堂1) ，黄运华2) ，张施琦3) ，丁 一1) ，闫小琴1) ，张 跃1) 1) 北京科技大学材料科学与工程学院，北京 100083 2) 北京科技大学新材料技术研究院，北京 100083 3) 长江大学机械工程学院，荆州 434023  通信作者，E-mail: xqyan@ mater． ustb． edu． cn 摘 要 采用光学显微镜、扫描电子显微镜和透射电子显微镜对热轧态和回火态 AH80DB 低碳贝氏体钢的显微组织、马氏 体/奥氏体( M/A) 岛、第二相的析出行为以及晶界取向差、有效晶粒尺寸进行研究，揭示回火后低碳贝氏体钢冲击韧性得到改 善的原因． 结果表明: 两种试样的组织均由板条状贝氏体、粒状贝氏体和针状铁素体组成，其中回火态试样中针状铁素体组 织较多． 热轧态钢中存在较大尺寸 M/A 岛且呈方向性分布，大角度晶界比例占 17. 33% ，有效晶粒尺寸为 3. 57 μm; 而回火态 钢中 M/A 岛的尺寸较小，大角度晶界比例增加 3. 43% ，有效晶粒尺寸减小 0. 56 μm． 热轧态钢中析出相主要是( Nb，Ti) C，尺 寸在 50 ～ 150 nm 之间，回火态试样中析出较多细小的球状( Nb，Ti) C 析出相，尺寸在 10 nm 左右． 关键词 低碳钢; 贝氏体; 冲击韧性; 显微组织; 析出相 分类号 TG142. 2 收稿日期: 2015--01--23 基金项目: 教育部创新团队和新世纪人才计划资助项目( IＲT1106) ; 高等学校学科创新引智计划资助项目( B14003) ; 中央高校基本科研业务 费资助项目( FＲF-As-13-001A) Microstructure and impact toughness of hot rolled and tempered low carbon bainitic steel AH80DB ZHAO Lei-chao 1) ，SUN Bin-tang1) ，HUANG Yun-hua2) ，ZHANG Shi-qi 3) ，DING Yi 1) ，YAN Xiao-qin1)  ，ZHANG Yue 1) 1) School of Materials Science and Engineering，University of Science and Technology Beijing，Beijing 100083，China 2) Institute for Advanced Materials and Technology，University of Science and Technology Beijing，Beijing 100083，China 3) College of Mechanical Engineering，Yangtze University，Jingzhou 434023，China Corresponding author，E-mail: xqyan@ mater． ustb． edu． cn ABSTＲACT The microstructure，martensite /austenite ( M/A) islands，precipitated phases，high-angle grain boundaries and effec￾tive grain size of hot rolled and tempered low carbon bainitic steel AH80DB were studied by scanning electron microscopy ( SEM) ， transmission electron microscopy ( TEM) and electron back-scattered diffraction ( EBSD) ． The reason for the improvement in impact toughness of the low carbon bainitic steel after tempering was discovered． The results show that the microstructures of both the samples mainly consist of lath bainite，granular bainite and acicular ferrite． There is more acicular ferrite in the tempered steel． Coarse M/A islands are found in the hot rolled steel and its distribution is directional，the ratio of large-angle grain boundaries is 17. 33% ，and the average effective grain size is 3. 57 μm． Nevertheless，the size of M/A islands decreases after tempering． Besides，the ratio of large￾angle grain boundaries increases by 3. 43% and the average effective grain size decreases by 0. 56 μm after tempering． The precipita￾ted phase of the hot rolled steel is ( Nb，Ti) C with the size of 50--150 nm，while much small and spherical precipitates with the size of about 10 nm appear after tempering． KEY WOＲDS low carbon steel; bainite; impact toughness; microstructure; precipitation