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Microscale-Calibrated Modeling of the Deformation Response of Dual-phase Steels

Peng Chen (Brown University), Hassan Ghassemi Armaki (Brown University), Sharvan Kumar (Brown University), Allan Bower (Brown University), Shrikant Bhat (ArcelorMittal Global R&D), Sriram Sadagopan (ArcelorMittal Global R&D)

Computational Materials Design via Multi-scale Modeling

Wed 10:45 - 12:15

Barus-Holley 190

A combination of micro-pillar compression tests and microstructure-based numerical simulations were used to determine the flow strength and strain partitioning in two commercial low-carbon dual phase steels, DP980 and DF140T.The two steels have significantly different microstructures: for example, the martensite volume fraction in DP980 is 61% while that in DF140T is 39%. Surprisingly, the two steels exhibit similar uniaxial stress-strain behavior. To determine the microstructural origin for this behavior, the mechanical response of the ferritic and martensitic phases in both steels were measured by extracting micron-scale compression specimens from the material, and deforming the pillars in uniaxial compression using a nanoindenter. The materials were characterized using a microstructure-based crystal plasticity model, which accounts for non-Schmid behavior in the ferritic phase, and contains a detailed description of the hierarchical microstructure of martensite. Material parameters were determined by fitting model predictions to the micro-pillar compression data. The crystal plasticity model was then used to predict the flow stress and strain partitioning during uniaxial tensile deformation of the two steels. The ferritic phases in the two steels were found to have similar flow strength. In contrast, the flow stress of martensite extracted from DF140T was found to be approximately twice that of DP980. This strength difference is offset by the difference in martensite volume fraction in the two steels, which consequently have nearly identical uniaxial tensile behavior. The strain partitioning and interfacial stress distributions in the two steels differ significantly, however, which has important implications on their tensile ductility.