Numerical Study on the Effects of Chemical Composition and Microstructure Inconsistencies on Mechanical Properties of Dual-Phase Steel

The chemical composition and microstructure of dual-phase steels from different production lines are inconsistent due to different manufacturing processes. It is responsible for the mechanical properties differences and brings negative impacts on the applications of DP steel during deformation. In this study, the chemical compositions, martensite volume fraction, and ferrite grain average diameter are investigated by the tests with DP780 steels from different production lines. The finite element models are established based on the microstructures of DP780 steels. Different mechanical properties of DP780 steels with various chemical compositions and microstructures are investigated on the stress-strain relationship and elongation by means of finite element simulation. A novel method with the failure element ratio as an indicator is proposed to evaluate the elongation of DP780 steel based on the micro-mechanism of tensile fracture. The quantitative effects are obtained separately in the forms of carbon content, martensite volume fraction, and ferrite grain average diameter on the mechanical properties of DP780 steel. It is suggested that the detailed chemical compositions and microstructures should be specified for the criterion of mechanical performance of DP steels.