Influence of strain path on nucleation and growth of voids in dual phase steel sheets

• Published in: Materials & design Vol. 92; pp. 1028 - 1037
• Main Authors: Samei, Javad, Green, Daniel E., Cheng, Jia, de Carvalho Lima, Murilo Soares
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 15.02.2016
• Subjects: Axial stress; Damage; Dual phase steel; Dual phase steels; Duplex stainless steels; Formability; Forming limit curve; Microstructure; Nucleation; Sheet metal; Strain; Strain path; Voids; Voids; Forming limit curve; Strain path; Microstructure; Dual phase steel
• ISSN: 0264-1275; 1873-4197
• DOI: 10.1016/j.matdes.2015.12.103

The objectives of this work are to describe the nucleation and growth of voids in DP600 dual phase steel sheets formed along different strain paths, and to investigate the correlation between the micro-mechanisms of damage and the forming limits. DP600 sheet specimens were stretch-formed in uniaxial, plane strain and biaxial tension using the Marciniak–Kuczynski formability test. The evolution of damage in the microstructure was correlated to the formability in each strain path by quantitatively analyzing void density, void area fraction, void aspect ratio and mean void size. Results showed that DP600 steel sheets have less formability in plane strain compared to uniaxial and biaxial tension due to the more rapid elongation and growth of voids. Moreover, the sheets safely deformed to much greater effective strains in biaxial tension due to the smaller mean void size and slower void growth. As proposed by Gurson Gurson (1977) , Tvergaard and Needleman Tvergaard and Needleman (1984) , void volume fraction is an important damage parameter. However, this work shows that void aspect ratio and mean void size also significantly influence the evolution of damage and the formability of dual phase steels. [Display omitted] •DP600 steel sheets were formed in different strain paths and the forming limit curve was obtained.•Micro-mechanisms of voids nucleation and growth are studied in different strain paths.•Quantitative analyses of voids are presented in 3D diagrams vs major and minor strains.•Correlation between evolution of voids and forming limits is discussed.•Fracture surfaces at different strain paths are described.