780MPa级热镀锌冷轧双相钢断裂过程的原位观察  

In-situ observation of fracture process for 780 MPa grade galvanized cold rolled dual phase steel

作　　者：宇文龙[1,2] 李声慈[1] 康永林[1] YU Wenlong LI Shengci KANG Yonglin(School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083, China Technical Research Institute, Shougang Co. Ltd., Beijing 100043, China)

机构地区：[1]北京科技大学材料科学与工程学院,北京100083 [2]首钢技术研究院,北京100043

出　　处：《中南大学学报（自然科学版）》2016年第10期3341-3346,共6页Journal of Central South University:Science and Technology

基　　金：国家自然科学基金资助项目(U1460101);国家高技术研究发展计划(863计划)项目(2013AA031601)~~

摘　　要：制备780 MPa级热镀锌冷轧双相钢,并对其组织性能进行测试分析;采用原位拉伸实验观察裂纹的萌生及扩展行为。研究结果表明:实验钢经热处理后获得铁素体+马氏体的双相组织;抗拉强度为789 MPa,屈强比为0.56,伸长率为23%,具有较好的力学性能;裂纹可以在铁素体内部或在铁素体-马氏体两相界上萌生;裂纹在扩展过程中遇到硬相马氏体岛时,会沿着马氏体岛的边缘绕过;铁素体产生的塑性变形能够减弱裂纹附近的局部应力集中,减缓裂纹扩展。双相钢的断口形貌是韧窝型,断裂形式属于塑性断裂。780 MPa grade galvanized cold rolled dual-phase steel was trial-produced, the microstructure and mechanical properties were tested. In-situ tensile test method was used to observe the crack initiation and propagation behavior. The results show that the dual phase steel consisting of ferrite ＋ martensite shows a tensile strength of 789 MPa, a yield ratio of 0.56, and an elongation of 23%. Cracks may derive from internal ferrite or ferrite-martensite phase boundary. When the cracks encounters hard martensite island during the expansion process, it will bypass the martensite and propagate along the edge of the islands. The plastic deformation near the crack of ferrite can weaken the local stress concentration, thus slowing crack growth. The final fracture pattern is plastic fracture, and the fracture morphology is a dimple pattern.

关 键 词：双相钢 断裂 原位观察 裂纹扩展 

分 类 号：TG142.1[一般工业技术—材料科学与工程]