Modeling Grain Boundary Motion and Dynamic Recrystallization in Pure Metals

Abstract

International audienceThe current study proposes a new approach of modeling discontinuous dynamic recrystallization in pure copper and cobalt based on the inverse analysis of experimental data. This approach comprises two steps: First, the mobility of grain boundaries is determined by a mean-field model in the steady state regime, then in a second step the information collected (mobility, nucleation frequency) is used to determine the mechanical behavior and the grain size change. The nucleation criterion is reformulated in a more general expression, and a new expression of the nucleation frequency with a single empirical parameter is proposed. The model predicts the stress-strain curves and the evolution of mean grain size, and is in good agreement with experimental data for both copper and cobalt. The modeling procedure requires a minimum of initial material parameters and could be especially attractive in the case of complex metals and alloys for which these parameters are unknown. (c) The Minerals, Metals & Materials Society and ASM International 201

Correlation between strain-rate sensitivity and dynamic softening behavior during hot processing

“…where c denotes the boundary energy and M BM represents the boundary mobility, which could be calculated by [32]:…”

The integrated influence on hot deformation of dual-phase titanium alloys incorporating dynamic recrystallization evolution and α/β phase transformation

“…Derived from K-M model and inverse proportion between θ and σ, a constitutive model could be constructed as Voce law given [7]:…”

Correlation between grain size and flow stress during steady-state dynamic recrystallization

“…K denotes a constant, usually within the range from 1 to 10, and n is a relevant exponent equal to 1/2$ 2/3. The Derby function has been validated with excellent application for the hot deformation of various alloy systems [12,13]. Stress-strain curves for the isothermal compression of austenitic steel alloy 800 H [6,7] are exhibited in Fig.…”

“…This phenomenon could also validate the Derby function, showing that the same stress levels under the DRX steady state correspond to similar grain sizes during hot deformation. With the assumption that non-distortion DRX grains nucleate and bulge spherically from the deformed portion, the thermodynamic condition for DRX steady state could be demonstrated as the balance between the boundary surface energy increases and the volume free energy decreases as [13]:…”

“…The mobility capacity increases with the temperature owing to the diffusion dependence. The boundary mobility is usually assumed to be proportional to the self-diffusivity at the grain boundaries, which could be calculated by [13]:…”