Micromechanical plastic behavior of dual-phase steels

What is it about?

In this study, a topology optimization based numerical method is proposed to investigate the micromechanical plastic behavior of dual-phase (DP) steels. Representative volume elements (RVEs) are constructed using the topology optimization based artificial microstructures. Micromechanical behavior under various loading conditions are predicted for the RVEs to investigate the plasticity, strain localization and strengthening mechanism affected by the microstructural characteristics of DP steels. Plastic strain patterns including shear band are found during the deformation. Due to the twisting movement of martensite grains, the direction of the strain localization bands in the shear loading case is or to the loading direction, while it is in the tensile and compressive cases. Moreover, the effective flow behavior of the material under shear loading is lower than those found in tensile and compressive cases. The influence of various microstructural features, such as, martensite fraction, distribution of each phase, on the effective flow properties and the local strain partitioning has also been identified. Both of the effective flow properties and strain localization exhibit the tendency to be strengthened with the increase of martensite phase fraction. Furthermore, the RVE with more uniform martensite distribution leads to the decrease of effective flow properties and strain localization. Longer martensite-ferrite interface results from the clustering of martensite, which increases the strain localization effect during the plastic deformation.

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Why is it important?

Dual-phase (DP) steel contains hard martensite islands embedded into a soft ferrite matrix. Due to this specific inhomogeneous microstructure, DP steel possesses excellent mechanical properties, e.g. relatively high ultimate tensile strength (UTS), low yield to tensile strength ratio and good balance between strength and formability. Hence, DP steel becomes a promising candidate material to manufacture the car bodies in automotive industry. However, the formability of DP steel depend on the processing methods, which are controlled either by plastic strain localization or by fracture. Therefore, this study give importance to understand the local micro mechanical behavior of DP steels, using a computational modelling approach

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