Transactions of Materials and Heat Treatment

Title：Fracture characteristics and mechanism on DP780 dual-phase steel under different strain states

Authors： Yu Li Liu Jing Ge Rui Wei Xing Peng Zhou Chen Ming Liu Dong

Unit： Wuhan University of Science and Technology Research Institute of Baoshan Iron & Steel Co. Key Laboratory of Development and Application Technology of Automotive Steels (BaoSteel)

KeyWords： DP780 dual-phase steel strain state fracture failure equivalent plastic fracture strain limited thinning rate phase interface stress concentration

ClassificationCode：TG386

year,vol(issue):pagenumber：2022,47(10):48-55

Abstract：

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.

Funds：

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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