Research on the evolving yielding behaviour and micro-mechanism in biaxial deformation of DP1180 sheet based on crystal plasticity finite element model

Abstract

Abstract Dual-phase steels (DP steels) consist of ferrite and hard martensitic phase. For the high strength and good formability, they are widely used in automotive applications. Compared with the DP steels with lower strength, DP1180 is more special for the volume fraction of martensite is higher than that of ferrite. In this paper, the evolving plastic yielding behaviours and insight into their microscale mechanisms of DP1180 were studied by biaxial tension experiments and crystal plasticity finite element method. The representative volume element (RVE) model of DP1180 taking the dual phase fraction, grain size and texture into consideration is established and the relevant parameters of crystal plasticity are reverse calibrated by the uniaxial tensile test stress strain curve. The simulated biaxial tension tests were conducted by the established RVE model to investigate the yielding micro-mechanisms of DP1180 steel, and the obtained yield loci matches well with the test results. The simulation results show that the texture has a significant effect on the contours of the yield loci. The soft ferrite grains weaken the kinetic constraints to the polycrystalline matrix and further free the rotation and plastic deformation of the neighbouring grains. This study thus provides a comprehensive understanding of the effect of the microstructure (crystal structure, texture and dual phase fraction) on the yielding behaviour of DP1180 steel as well as a method of virtual experiment to get the yield loci of metallic materials.