 Calphad: CALculation of PHAse Diagrams 
Definition:  Computer coupling of
phase diagrams and
thermochemistry. 
Explanation:  Phase diagrams are a
very powerful tool
for predicting the
state of a system
under different
conditions. The
Calphad approach is
based on the fact
that a phase diagram
is manifested by the
equilibrium
thermodynamic
properties of the
system. Hence, it is
possible to
calculate a phase
diagram by modeling
the thermodynamic
properties of all
the phases in a
system. By combining
the models for
several low order
systems, it is
possible to
construct
multicomponent
databases, which can
be used to predict
the state of
multicomponent
alloys.
Obvious applications
include the direct
calculation of phase
diagrams, phase
equilibria and
thermodynamic
properties such as
Gibbs energies,
chemical potentials,
activities,
enthalpies and heat
capacities using
software such as
ThermoCalc.
The Calphad method
also forms the basis
for simulation of
phase
transformations
using phase
field modeling
or diffusion
simulation methods
(→DICTRA)
and for process
simulation, which
makes it to be one
of the
key tools for ICME
(Integrated
Computational
Materials
Engineering).

Picture / Figure / Diagram: 

(a) Overview of the Calphad method, (b) Calculated isothermal section of the FeMnC phase diagram.


SFBLink:  Within the SFB the Calphad method is used for the calculation of stacking fault energy (→SFE), T_{0}, M_{s} for εmartensite as well as more conventional phase equilibria and phase diagrams which are used to predict solidification ranges, microsegregation, formation of carbides (cementite and kappa carbide) and other phases. It is also used for the calculation of solubilities of gaseous elements such as nitrogen and hydrogen. 
References:  HL Lukas, SG Fries, B Sundman, Computational Thermodynamics – The Calphad Method, Cambridge University Press, Cambridge, UK, 2007. D Djurovic, B Hallstedt, J von Appen, R Dronskowski, Calphad, 35, 479491(2011). 

