Constitutive relationships for 22MnB5 boron steel deformed isothermally at high temperatures

The strain, strain rate and temperature dependency of a boron steel, which was isothermally deformed under uniaxial compression tests, has been investigated at temperatures between 600 and 900°C, and at strain rates of 0.1, 1.0 and 10.0 s−1. Two constitutive models were used to correlate the plastic behavior: the Voce constitutive relation in combination with the kinetic model proposed by Kocks and the phenomenological model proposed by Molinari–Ravichandran. The Kocks model has been introduced in the Voce formulation to describe the temperature and the strain rate dependency of the saturation stress and of the yield stress. The Molinari–Ravichandran model is based on a single internal variable that can be viewed as being related to a characteristic length scale of the microstructure that develops during deformation. It has been shown that the plastic behavior of the boron steel can be well described using these two models.