Atomistically Informed Extended Gibbs Energy Description for Phase-Field Simulation of Tempering of Martensitic Steel
O. Shchyglo, T. Hammerschmidt, C. Miroslav, R. Drautz , I. Steinbach,
Volume: 9. Pages: 669
DOI: 10.3390/ma9080669
Published: 2016
Abstract
In this study we propose a unified multi-scale chemo-mechanical description
of the BCT (Body-Centered Tetragonal) to BCC (Body-Centered Cubic)
order-disorder transition in martensitic steel by adding the mechanical
degrees of freedom to the standard CALPHAD (CALculation of PHAse
Diagrams) type Gibbs energy description. The model takes into account
external strain, the effect of carbon composition on the lattice
parameter and elastic moduli. The carbon composition effect on the
lattice parameters and elastic constants is described by a sublattice
model with properties obtained from DFT (Density Functional Theory)
calculations; the temperature dependence of the elasticity parameters
is estimated from available experimental data. This formalism is
crucial for studying the kinetics of martensite tempering in realistic
microstructures. The obtained extended Gibbs energy description opens
the way to phase-field simulations of tempering of martensitic steel
comprising microstructure evolution, carbon diffusion and lattice
symmetry change due to the ordering/disordering of carbon atoms under
multiaxial load.