Individual phase constitutive properties of a TRIP-assisted QP980 steel from a combined synchrotron X-ray diffraction and crystal plasticity approach

• Published in: Acta materialia Vol. 132; pp. 230 - 244
• Main Authors: Hu, X.H., Sun, X., Hector, L.G., Ren, Y.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Ltd 15.06.2017; Elsevier
• Subjects: CRSS and hardening parameters; Crystal plasticity finite element model; Elastic plastic self-consistent model; Quench and partitioning steels; Synchrotron radiation; X-ray diffraction; X-ray diffraction; Quench and partitioning steels; CRSS and hardening parameters; Crystal plasticity finite element model; Synchrotron radiation; Elastic plastic self-consistent model
• DOI: 10.1016/j.actamat.2017.04.028
• ISSN: 1359-6454

Microstructure-based constitutive models for multiphase steels require accurate constitutive properties of the individual phases for component forming and performance simulations. We address this requirement with a combined experimental/theoretical methodology which determines the critical resolved shear stresses and hardening parameters of the constituent phases in QP980, a TRIP assisted steel subject to a two-step quenching and partitioning heat treatment. High energy X-Ray diffraction (HEXRD) from a synchrotron source provided the average lattice strains of the ferrite, martensite, and austenite phases from the measured volume during in situ tensile deformation. The HEXRD data was then input to a computationally efficient, elastic-plastic self-consistent (EPSC) crystal plasticity model which estimated the constitutive parameters of different slip systems for the three phases via a trial-and-error approach. The EPSC-estimated parameters are then input to a finite element crystal plasticity (CPFE) model representing the QP980 tensile sample. The predicted lattice strains and global stress versus strain curves are found to be 8% lower that the EPSC model predicted values and from the HEXRD measurements, respectively. This discrepancy, which is attributed to the stiff secant assumption in the EPSC formulation, is resolved with a second step in which CPFE is used to iteratively refine the EPSC-estimated parameters. Remarkably close agreement is obtained between the theoretically-predicted and experimentally derived flow curve for the QP980 material. [Display omitted]