IWPDF2023

Investigation of Failure Mechanisms in Dual-Phase Steels through Micromechanics-Based Frameworks

I.U. Aydiner ∗ , B. Tatli, T. Yalçinkaya

Department of Aerospace Engineering, Middle East Technical University, Ankara 06800, Türkiye

∗ aydiner.umay@metu.edu.tr

Keywords: dual-phase steel, crystal plasticity, cohesive zone modeling, ductile fracture.

Due to their special composition, which combines the ductile ferrite phase with the hard and brittle martensite phase, dual-phase (DP) steels have excellent formability and intriguing material properties. However, this incompatible deformation behavior of two phases within DP steels results with complicated failure mechanisms in micro-scale. These include martensite cracking and interface decohesion between the ferrite-martensite (F/M) and ferriteferrite (F/F) phases [1, 2]. A detailed analysis of DP steel microstructure using a micromechanics-based methodology is required in order to understand their plastic and failure behavior. To capture the impact of microstructure evolution on macroscopic response, a crystal plasticity and cohesive zone modeling based failure framework for three-dimensional Representative Volume Element (RVE) calculations is used. For the brittle martensite phase, the isotropic J2 plasticity model is used, whereas the rate dependent crystal plasticity framework is used for the ductile ferrite phase. To study intergranular cracking, cohesive zone elements are inserted at the F/M and F/F interfaces. Additionally, an uncoupled damage model is used to model intragranular failure in the martensite phase. To calibrate the aforementioned failure models, a comprehensive parameter identification study is carried out. The ability of the framework to predict the failure and plastic responses in comparison to the findings in the literature is assessed [3]. This is achieved through analyzing and discussing a variety of threedimensional polycrystalline RVEs with diverse microstructural properties including the effect of addition of simulated cohesive interfaces, crystallographic orientation, martensite morphology, stress triaxiality and martensite volume fraction. Critical factors determining the failure mechanisms in dual-phase steels have been identified as the morphology of the martensite phase and the triaxial stress state that the material experiences. References [1] Tang, A., Liu, H., Chen, R., Liu, G., Lai, Q., Zhong, Y., Wang, L., Wang, J., Lu, Q., and Shen, Y. (2021). Mesoscopic origin of damage nucleation in dual-phase steels. Int. J. Plast., 137, 102920. [2] Lai, Q., Bouaziz, O., Gouné, M., Brassart, L., Verdier, M., Parry, G., Perlade, A., Bréchet, Y., and Pardoen, T. (2015). Damage and fracture of dual-phase steels: Influence of martensite volume fraction. Mater. Sci. Eng. A, 646, 322–331. [3] Yalçinkaya, T., Tatli, B., Ünsal, I.E., Aydiner, I.U. (2022). Crack initiation and propagation in dual-phase steels through crystal plasticity and cohesive zone frameworks. Procedia Struct. Integrity, 42, 1651-1659.

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