深过冷条件下珠光体特征尺寸及断裂行为分析  

Analysis of characteristic dimension and fracture behavior of pearlitic steel under deep undercooling conditions

作　　者：孟灿 徐平伟[1,2,3] 李静 梁宇[1,2,3] MENGCan;XUPingwei;LIJing;LIANGYu(School of Materials and Metallurgy,Guizhou University,Guiyang 550025,Guizhou,China;Guizhou Key Laboratory of Material Structure and Strength,Guiyang 550025,Guizhou,China;National and Local Joint Engineering Laboratory of High Performance Metal Structural Materials and Manufacturing Technology,Guiyang 550025,Guizhou,China;Department of Equipment Support and Remanufacturing,Army Academy of Armored Forces,Beijing 100072,China)

机构地区：[1]贵州大学材料与冶金学院,贵州贵阳550025 [2]贵州省材料结构与强度重点实验室,贵州贵阳550025 [3]高性能金属结构材料与制造技术国家地方联合实验室,贵州贵阳550025 [4]陆军装甲兵学院装备保障与再制造系,北京100072

出　　处：《钢铁研究学报》2021年第1期75-83,共9页Journal of Iron and Steel Research

基　　金：国家自然科学基金资助项目(51901053,51461007);贵州省自然科学基金资助项目([2017]5788)。

摘　　要：采用扫描电镜(SEM)、透射电镜(TEM)、Instron拉伸机、原位拉伸等实验方法,研究了深过冷工艺对珠光体特征尺寸及断裂行为的影响。结果表明:在相同奥氏体晶粒尺寸条件下,过冷奥氏体通过深过冷条件后,比直接等温所得的珠光体团尺寸降低47.9%,珠光体平均片层间距细化12%。拉伸性能表明,在相同等温温度下,通过深过冷后的试样塑性指标明显提升。原位拉伸观察发现,直接等温试样珠光体团较大,变形协调性较差,微裂纹易在珠光体团内萌生,而深过冷试样珠光体团较细,珠光体团之间变形协调性更好,拉伸变形过程中裂纹萌生位置较少。对比断口附近裂纹扩展路径,直接等温试样中裂纹沿Fe_(3)C/α-Fe片扩展,而深过冷试样中裂纹沿珠光体团界扩展,因此通过调整相变条件实现对珠光体团尺寸的细化,能改变裂纹萌生扩展特点,提高材料塑性指标。The effects of deep undercooling process on the characteristic dimension and fracture behavior of pearlite were studied. Methods of scanning electron microscopy(SEM), transmission electron microscopy(TEM), tensile testing with Instron machine, and in-situ tensile test were used. The results indicate that, for an undercooled austenite subjected to deep undercooling conditions, its colony dimensions and average lamellar spacing of pearlite reduce by 47.9% and 12%, respectively, compared to those of pearlite obtained from austenite with the same grain size and produced by direct isothermal method. The tensile test results indicate that, under the same isothermal conditions, the plasticity index of the specimen is clearly enhanced after deep undercooling. The results of the in-situ tensile test indicate larger pearlite colonies and a poor deformation compatibility between the pearlite colonies in the direct isothermal samples. Therefore, micro-cracks are readily initiated across the pearlite colonies. On the other hand, refined pearlite colonies and an appropriate deformation compatibility between the pearlite colonies have been observed in the deep undercooled specimens. Accordingly, the initiation positions of cracks during the tensile deformation process are less in the undercooled samples compared to those in the direct isothermal samples. In addition, the cracks near the fracture surface of the direct isothermal sample propagate along the Fe_(3)C/α-Fe sheet while those of undercooled specimens propagate the boundaries of pearlite colonies. Therefore, the dimension of pearlite colonies can be refined by adjusting the phase transformation conditions. Moreover, the modification can alter the initiation and propagation characteristics of cracks, and significantly enhance the plasticity index of the material.

关 键 词：深过冷 珠光体特征尺寸 断裂行为 原位拉伸 裂纹路径 

分 类 号：TG161[金属学及工艺—热处理] TG115.21[金属学及工艺—金属学]