20CrMnTi钢马氏体多层次结构及TiN夹杂对断裂韧度的影响  

Influence of martensitic multi-level structure and TiN inclusions on fracture toughness of 20CrMnTi steel

作　　者：龙绍檑 朱单单 罗相兰 易艳良 杨明[4] 卢叶茂 梁益龙[4] Long Shaolei;Zhu Dandan;Luo Xianglan;Yi Yanliang;Yang Ming;Lu Yemao;Liang Yilong(School of Materials and Energy Engineering,Guizhou Institute of Technology,Guiyang Guizhou 550003,China;Guizhou Yonghong Heat Transfer and Cooling Technology Co.,Ltd.,Qiannan Guizhou 550601,China;School of Chemical Materials,Jinan University,Guangzhou Guangdong 510632,China;School of Materials and Metallurgy,Guizhou University,Guiyang Guizhou 550025,China)

机构地区：[1]贵州理工学院材料与能源工程学院,贵州贵阳550003 [2]贵州永红换热冷却技术有限公司,贵州黔南550601 [3]暨南大学化材学院,广东广州510632 [4]贵州大学材料与冶金学院,贵州贵阳550025

出　　处：《金属热处理》2025年第2期43-51,共9页Heat Treatment of Metals

基　　金：贵州省基础研究计划(自然科学类)(黔科合基础[2020]1Y199);高层次人才科研启动经费项目(XJGC20190949)。

摘　　要：采用三点弯曲试样测试了20CrMnTi钢的断裂韧度(K_(IC)),发现K_(IC)值随晶粒粗化而降低,这与其他低碳板条马氏体钢K_(IC)和晶粒尺寸的关系相矛盾。基于此,通过OM、EBSD、SEM等方式及热力学模型、断裂力学模型对20CrMnTi钢的断裂行为进行了分析。结果表明,基于Hall-Petch方程建立的20CrMnTi钢多层次组织与K_(IC)的关系发现,马氏体板条块(Block)是其断裂韧度的有效晶粒,但断裂形貌分析显示,20CrMnTi钢粗晶和细晶状态的有效晶粒不同。进一步分析发现,断口上存在一定数量的不规则TiN夹杂,热力学计算显示TiN夹杂形成于液相区,尺寸较粗大,很容易导致裂纹萌生。借助SEM和断裂力学计算对裂纹扩展进行分析,发现20CrMnTi钢细晶状态下裂纹扩展曲折进行,且横切板条马氏体束,导致其获得较好断裂韧度,而粗晶状态下裂纹路径平直,展现出较差的韧性。因此,TiN夹杂的形成是导致20CrMnTi钢的断裂韧度发生突变的关键因素,该研究结果对高性能20CrMnTi钢的制备具有重要指导意义。Fracture toughness(K_(IC))of 20CrMnTi steel was tested by using three-point bending specimens,and it was found that the value of K_(IC)decreases with grain coarsening,which contradicts the relationship between the K_(IC)and the grain size of other low carbon lath martensitic steels.Based on this,the fracture behavior of the 20CrMnTi steel was analyzed by means of OM,EBSD,SEM and thermodynamic model,fracture mechanics model.The results show that the relationship between the multi-level microstructure of the 20CrMnTi steel and K_(IC)established based on the Hall-Petch equation reveals that the martensitic lath block is the effective grain for fracture toughness.Still,the fracture morphology analysis reveals that the effective grains in the coarse or fine grain states of the 20CrMnTi steel are different.Further analysis reveals the presence of a certain number of irregular TiN inclusions on the fracture,and thermodynamic calculations show that the TiN inclusions are formed in the liquid-phase region with coarse size,which can easily lead to crack initiation.The crack propagation is analyzed with the help of SEM and fracture mechanics calculations,revealing that the crack propagation in the fine grain state of the 20CrMnTi steel is zigzagging and cross-cutting the lath martensite packet,which leads to a better fracture toughness,whereas the crack path in the coarse grain state is straight and shows a poor toughness.Therefore,the formation of TiN inclusions is the key factor leading to the abrupt change in fracture toughness of the 20CrMnTi steel,and the results of this study are of great significance in guiding the preparation of the high-performance 20CrMnTi steel.

关 键 词：低碳20CrMnTi钢 板条马氏体 多层次结构 TIN 断裂韧度 

分 类 号：TG142.13[一般工业技术—材料科学与工程]