A novel crystal plasticity model incorporating transformation induced plasticity for a wide range of strain rates and temperatures

• Published in: International journal of plasticity Vol. 152; p. 103188
• Main Authors: Connolly, D.S., Kohar, C.P., Inal, K.
• Format: Journal Article
• Language: English
• Published: New York Elsevier Ltd 01.05.2022; Elsevier BV
• Subjects: Axial stress; Calibration; Crystal dislocations; Crystal plasticity; Crystal structure; Evolution; Fracture toughness; High strength steels; Martensite; Martensitic transformations; Plane strain; Plastic properties; Retained austenite; Strain rate; Strain-rate dependence; Temperature; Temperature dependence; Thermo-mechanical modeling; Transformation induced plasticity; Thermo-mechanical modeling; Crystal plasticity; Temperature dependence; Strain-rate dependence; Transformation induced plasticity
• ISSN: 0749-6419; 1879-2154
• DOI: 10.1016/j.ijplas.2021.103188

Transformation induced plasticity (TRIP) is an effect common to several classes of advanced high strength steels (AHSS) with promising automotive applications. This effect is characterized by the transformation of retained austenite (RA) to martensite, resulting in increased hardening, increased fracture resistance, and improved formability. Accurate thermo-mechanical modeling over a range of strain-rates and temperatures is critical to fully utilize the improved performance of AHSS exhibiting the TRIP effect. In this work, a novel thermodynamically consistent rate-dependent crystal plasticity formulation is developed, which incorporates strain-rate and temperature dependent strain-induced martensitic transformation. Thermodynamic arguments are used to derive plastic slip and transformation driving forces accounting for various physical mechanisms (e.g. applied stress, temperature, crystal orientation, stored dislocation energy), as well as a constitutive law governing temperature evolution. RA and transformed martensite mechanical thermo-elasto-viscoplastic behavior is explicitly modeled, and a modified Taylor homogenization law is proposed to determine strain partitioning while accounting for transformation. The model is then calibrated and validated for a QP3Mn alloy over a large range of temperatures (-10°C–70°C) and strain-rates (5 × 10-4s−1–200s−1). The evolution of the Taylor–Quinney coefficient and the orientation dependence of transformation are found to match well with trends in literature. The fully calibrated model is compared to a model recalibrated without strain-rate dependent transformation, demonstrating that capturing strain-rate dependent transformation may be necessary even for materials where no direct experimental strain-rate dependence. Plane strain and equibiaxial tension simulations are conducted using the calibrated model, showing that increasing triaxiality results in increased transformation. An extension to the calibrated model is proposed for materials which do not match the predicted trend. •Novel modified Taylor homogenization of mechanical and thermodynamic behavior.•Novel transformation kinetics law capturing strain-rate and temperature dependence.•First TRIP CP model calibrated and validated over wide range of strain rates and temperatures.•Results highlight importance of rate-dependent transformation.•Strain path analysis predicts increasing transformation with triaxiality.