锻压技术

DP780双相钢在不同应变状态下的断裂特性及机理

英文标题：Fracture characteristics and mechanism on DP780 dual-phase steel under different strain states

作者：余立刘静葛锐魏星彭周陈明刘冬

关键词：DP780双相钢应变状态断裂失效等效塑性断裂应变极限减薄率相界面应力集中

分类号：TG386

出版年,卷(期):页码：2022,47(10):48-55

摘要：

先进高强钢（AHSS）是重要的汽车轻量化材料，其在不同应变状态下会表现出不同的断裂特性。以DP780双相钢为研究对象，研究了其在典型应变状态下的断裂失效行为，并对试样的微观组织和断口形貌进行了观察和表征，分析了DP780双相钢在不同应变状态下断裂的微观机理。研究表明：随着应变比的提高，等效塑性断裂应变ε-f先减小后增大；平面应变状态下ε-f最小，等轴拉伸应变状态下ε-f最大。应变状态对DP780双相钢的断裂特性和失效有重要影响：平面应变状态下，试样芯部的厚向应变梯度和三向拉应力状态增加了变形的不协调程度，加速了微孔洞的萌生和生长，相对于单轴拉伸更容易产生厚向裂纹而发生撕裂；等轴拉伸应变状态下，材料变形均匀，厚向应变梯度小，孔洞的萌生和生长受到抑制，从而使DP780双相钢在等轴拉伸应变状态下的等效塑性断裂应变最大。

Advanced high strength steel (AHSS) is an important material for lightweight in automobile, which performs different fracture characteristics under different strain states. Therefore, for DP780 dual-phase steel, the fracture failure behavior under typical strain state was studied. Then, the microstructure and fracture morphology of samples were observed and characterized, and the fracture micro-mechanism of DP780 dual-phase steel under different strain states was analyzed. The results show that with the increasing of strain ratio, the equivalent plastic fracture strain εf decreases first and then increases, εf is the smallest under plane strain state. And the largest under equiaxial tension strain state. And the strain state has a significant effect on the fracture characteristics and failure of DP780 dual-phase steel. Under the plane strain state, the strain gradient along the thickness direction and the triaxial tensile stress state in the material core increase the inconsistency degree of deformation, accelerate the initiation and growth of micro-voids, and are more likely to produce cracks along the thickness direction and tear compared with the uniaxial tensile state. Under the equiaxial tension strain state, the material deforms uniformly, the stain gradient along the thickness direction is small, and the initiation and growth of pores are inhibited so that the equivalent plastic fracture strain of DP780 dual-phase steel under the equiaxial tensile strain state is the largest.

基金项目：

国家自然科学基金资助项目（U20A20270）

余立（1984-），男，博士研究生，高级工程师,E-mail：yu.li@baosteel.com;通信作者：刘静（1964-），女，博士，教授,E-mail：liujing@wust.edu.cn

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