New functionalities of TC-DICTRA
Thermo-Calc Anwendertreffen und Schulung
Aachen 11-13th of June 2003
Dr. Anders Engström
Thermo-Calc Software
Stockholm Technology Park
SE-113 47 Stockholm, Sweden
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Outline
ƒ Introduction
ƒ Thermo-Calc Classic, version P
ƒ Thermo-Calc for Windows, TCW2.2
ƒ DICTRA, version 22
ƒ Programming interfaces
ƒ Databases
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History of Thermo-Calc
ƒ First version of Thermo-Calc was created in 1981.
First sale was made in 1984. First sale of DICTRA
somewhat later in 1994.
ƒ The team of researchers behind the software
worked at the department of Physical Metallurgy
at the Royal Institute of Technology
ƒ In the beginning the department was the base for
development and distribution of the software
packages.
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History of Thermo-Calc
To protect the software Thermo-Calc and
DICTRA the researcher created a foundation
and donated their software rights to:
“Stiftelsen för Tillämpad Termodynamik”
or
Foundation of Computational Thermodynamics
(Current chairman: Bo Jansson)
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History of Thermo-Calc
In 1997 it was realised that the department was not
suited to be the base of a sizable software operation
and the foundation created the company:
”Thermo-Calc Software AB”
to take care of software maintenance, development
and distribution.
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History of Thermo-Calc
Today Thermo-Calc Software is the exclusive
distributor of the software with agents in USA,
Germany, Japan, China and South America.
The foundation benefits from royalty payments
which are used for grants to young researchers
and to support of various projects in the filed of
computational thermodynamics.
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Thermo-Calc Classic, version P
ƒ New features and commands in TDB, GES5,
POLY3, POST, PARROT and ED_EXP modules
ƒ Modifications to some special modules, i.e. BIN,
SCHEIL and POURBAIX
ƒ Improved documentation
ƒ Increased example collection
ƒ Improved graphics & 3D presentation
ƒ Some bugs have been corrected
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DATABASE_RETRIEVAL (TDB)
ƒ New Command: SET_AUTO_APPEND
For conveniently appending a database
with the same system definition
ƒ Automatic conversion of database files for
compatibility between Unix and
PC/Windows
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GIBBS_ENEGRY_SYSTEM (GES5)
ƒ The maximum number of constituents in a
non-ideal phase has been increased from 80
200. Ideal phases can have 1000 constituents.
Needed for solution phases with many
associates or for aqueous solutions, in
complex heterogeneous interaction systems.
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POLY_3
ƒ Improved convergence in the commands:
COMPUTE_EQUILIBRIUM
COMPUTE_EQUILIBRIUM *
ƒ MAP and STEP somewhat modified
ƒ Possibility to check internal stability of phases using:
STABILITY_CHECK
in the
SPECIAL_OPTIONS command
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POLY_3
ƒ Improvements in the command:
COMPUTE_TRANSITION
Now possible to look for any new phase
appearing when one conditions is varied
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TCP Example
ƒ Calculation of phase transitions in the alloy Ti10Al-2V using COMPUTE_TRANSITION
ƒ Exploring the new graphics
ƒ Dumping diagrams
ƒ Using C-E *
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POLY_3
ƒ Calculation of T0-temperature
The temperature or composition where the two phases
have the same Gibbs energy
T
α
γ
T0-line
Gm
G γm
G αm
T=T0 for X=X1
X1
X
X
This is usually regarded as the thermodynamic limit for a
partitionless transformation
Implemented in the SPECIAL_OPTIONS command and
as an option in STEP
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POLY_3
ƒ Calculation of paraequilibrium
%M
T0
.
γ
α
Paraequilibrium or partial
equilibrium occur when one
component in an alloy diffuse
much faster than the others.
%C
Conditions allow a partly partitionless transformation, where the
new phase can form with different content of the mobile component,
but with the same composition of the slow diffusing components.
Implemented in the SPECIAL_OPTIONS command and
as an option in STEP
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POLY_3
%M
γ
T0
Iso-activity line for C in γ
.
%M
ν
Slow
•
α
•
fα
fγ
Rapid transformation
Iso-activity line for C in α
%C
Distance
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TCP Example
ƒ Calculation of a T0-line and a phase diagram
according to paraequilibrium conditions for γ
to α transformations in a Fe-1.5Mn-0.3Si-C
alloy
ƒ Also, we will calculate an isothermal section
of a phase diagram for Fe-Mn-0.3Si-C and
append a calculated diagram according to
Paraequilibrium conditions
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POST
ƒ Conditions and database name are displayed
in diagram when plotting
ƒ New command: CREATE_3D_PLOTFILE
Creates vrml-file (Virtual Reality Modelling
Language) from tabulated data.
Makes it possible to view both squared, triangular
and tetrahedral diagrams using one of many plugins freely available for web browsers.
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Example of VRML viewers for Internet Explorer
and Netscape Navigator
ƒ For Windows and Mac:
Cortona WRML Client from Parallelgraphics
www.parallelgraphics.com
ƒ For Windows, Linux and SIG IRIX 6.2:
VRMLview from Systems in Motion (SIM)
www.sim.no
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TCP Example
ƒ Calculate the “γ-volume” in the system
Fe-Cr-C
ƒ Also, we will take a look at some liquidus
surfaces as well as the “γ-volume” for the
Fe-Cr-V-C system
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Edit-Experiments (ED_EXP)
Now possible to store and restore a weight set that records all the
weights given to different experimental points in an assessment,
using the new commands STORE_ALL_WEIGHTS and
RESTORE_ALL_WEIGHTS.
It is also possible to list out all the calculated equilibrium points
(using the LIST_ALL_EQUILIBRIA command) and to
immediately calculate property diagrams with selective stepping
options in which the calculations and the set stepping variable are
based on a specific experimental point (using the
GRAPHICS_PLOT command, which is identical to the
STEP_WITH_OPTIONS command in the POLY module).
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TCW2
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TCW2.2
ƒ TCC version P DLL engine
ƒ Database information displayed on request
ƒ Possibility to append databases
ƒ Possibility to use functions in the post module
ƒ Improved show value feature
ƒ Improved MACRO management
ƒ Some other small improvements, e.g. re-entrant
function
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TCW2.2 Example
ƒ Calculation of Pitting Resistance Equivalence
(PRE) in a duplex stainless steel:
¾How to view database information
¾How to Append a database
¾How to change phase status
¾How to enter functions and tables
¾Exploring the show value feature
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Example: PRE in a duplex stainless steel
• PRE (Pitting Resistance Equivalence) is a
empirical measure for corrosion resistance in
stainless steels.
• One definition of PRE is:
PRE=w%Cr+3,3*w%Mo+16*w%N
• For duplex stainless steels, it is desirable to have a
high and balanced PRE-numbers in ferrite and
austenite.
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DICTRA version 22
ƒ TCC version P thermodynamic engine
ƒ Larger workspaces to handle simulations with >10
elements
ƒ Possibility to simulate interfacial mobility controlled phase
transformations. Achieved by adding a Gibbs-energy
contribution to the growing phase
ƒ Model for diffusion in stoichiometric phases without any
freedom, such as A2B
ƒ Numerical integration/differentiation of curves in the post
processor
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Diffusion in stoichiometric phases
BCC +
Al2Fe
Al13Fe4
BCC
Al2Fe
Al5Fe2
Model:
Al13Fe4
BCC
Al2Fe
Al5Fe2
Fe-Al
FCC
FCC +
Al13Fe4
C
'
J k = − ∑ < Lkj >
j= 1
∆ µj
λ
(Ågren)
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Diffusion of C in Cementite (Fe3C)
Experimental data from Ozturk et al.
Experimental data from Schneider et al.
(Höglund, 2002)
Experimental information on the growth of cementite layers
at different carbon activities
Mobility of C in cementite evaluated from this data
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Evaluation of mobility for C in Cementite
ƒ Mobility of C evaluated for each activity
ƒ The average mobility determined at each temperature
ƒ The logarithm of the mobility assumed to have a linear
temperature dependency
ƒ Finally, the parameters M0 and Q in the expression below
were assessed
M
Cem
C
= M0 ⋅e
− Q / RT
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Solidification simulations
Equilibrium methods (lever-rule)
Solute diffusion is rapid, i.e. complete solute back diffusion → uniform
composition in both solids and liquid
Non equilibrium methods (SCHEIL)
Negligible diffusion in solids, i.e. no solute back diffusion → solids retain
same composition through solidification
Partial equilibrium methods (SCHEIC)
Complete interstitial but negligible substitutional solute back diffusion
Moving phase boundary methods (DICTRA)
Full integration of thermodynamics and kinetics
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Solidification simulations
Alloy:
Fe- 5%Cr – 1%C – 2%V -8%W
Lever rule
SCHEIC
SCHEIL
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SCHEIC (SCHEil with Interstitial Carbon)
ƒ Basically a SCHEIL model for the substitutional
components, with the addition that interstitial components
are allowed to move freely among the liquid and all portions
of the solid phases, so that their chemical potentials becomes
equal everywhere throughout the whole system.
Status
ƒ TCS has developed an application program with the aid of
the TQ interface.
Future
ƒ A separate module is planed to be available in TCQ and
TCW 3.0
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Solidification simulations using DICTRA
Assumptions:
ƒ Assuming that equilibrium hold locally at the phase
interface.
ƒ Assumption regarding the geometry and size of the
system, e.g. the interdendritic spacing.
ƒ Assumption regarding the cooling rate.
However,
ƒ Full consideration of diffusion in both the liquid and
solid phases.
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DICTRA Example
Microsegregation during solidification:
Bcc
Liquid
Fcc
υ
Bcc
Liquid
υ
Bcc
υ
Fcc
Fcc
Liquid
υ
Liquid
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DICTRA Example cont.
ƒ Secondary dendrite arm spacing assumed to be 200 µm.
ƒ Cooling rate assumed to be 0.2 ºC/s.
Inactive phases
Bcc
Fcc
λ/2 =100 µm
Liquid
λ/2
Temperature function:
1780 – 0.2 • TIME
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Thermo-Calc Programming Interfaces
New Versions of:
ƒ TC-API (Thermo-Calc Application Programming Interface)
¾ For Windows programming
¾ Written in C
¾ Available for Windows and Linux environments
ƒ TQ-I (Thermodynamic Calculation Interface)
¾ Written in FORTRAN
¾ Available for all UNIX dialects and Windows.
ƒ TC-Toolbox in MATLAB®
¾ Available for Windows.
All new versions based on Thermo-Calc version P
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TQ-I version 4.0
Now also possible to calculate kinetic coefficients,
e.g. atomic mobilities, tracer diffusion, chemical
diffusion and intrinsic diffusion coefficients
All syntaxes the same as in DICTRA, e.g.
M(Phase,J)
Mobility coefficient where J=diffusing specie
DT(Phase,J)
Tracer diffusion coefficient where J=diffusing specie
DC(Phase,J,K,N)
Chemical diffusion coefficient where
K=gradient specie, and N=reference specie
DI(Phase,J,K,N)
Intrinsic diffusion coefficient
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TCFE3
Thermo-Calc Software Steel database version 3
ƒ Update of TC-FE2000
ƒ Released with TCC version P
ƒ For Fe-rich alloys with the alloying elements:
Al-B-C-Co-Cr-Cu-Mg-Mn-Mo-N-Nb-Ni-O-P-S-Si-Ti-V-W
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TCFE3
Improvements:
ƒ Improved data for sigma phase in stainless steel.
ƒ Data added in the Nb-Ni, Fe-Cr-Mo and Cr-Mo-Ni
systems.
ƒ Improved data for the Ti(C,N) fcc-carbonitride.
ƒ Improvements in starting values.
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TCFE3
Comparison to experimental liquidus data for low
alloy steels, tool steels and stainless steels
Liquidus
1550
1525
Calculated value
1500
1475
1450
1425
1400
Data from:
Jernkontoret ” A Guide to the Solidification of Steels”
1375
1350
1350
1375
1400
1425
1450
1475
1500
1525
1550
Experimental value
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TCFE3
Comparison to experimental solidus data for low
alloy steels, tool steels and stainless steels
S olidus
Calculated value
1500
1400
1300
Data from:
Jernkontoret ” A Guide to the Solidification of Steels”,
where a cooling rate of 0.1°C/s was used
1200
1100
1100
1200
1300
1400
1500
Ex pe rim e nta l va lue
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TCFE3
Comparison to experimental equilibrium austenite composition
in different multicomponent, multiphase stainless steels
C h r o m iu m c o n te n t in Au s te n ite (m a s s -% )
30
Calculated value
25
20
15
10
Data from:
S.M. Wessman et al., EC Report EUR20315 EN
5
0
0
5
10
15
20
25
30
E x p e r i m e n ta l v a l u e
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TCFE3
Comparison to experimental equilibrium austenite composition
in different multicomponent, multiphase stainless steels
M o lyb d e n u m co n te n t in F e rrite (mass-%)
6.00
Calculated value
5.00
4.00
3.00
2.00
Data from:
S.M. Wessman et al., EC Report EUR20315 EN
1.00
0.00
0.00
1.00
2.00
3.00
4.00
5.00
6.00
Experim ental value
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TCFE3
Comparison to experimental equilibrium fractions of ferrite and
sigma-phase for a duplex stainless steel as a function of temperature
α
σ
Data from:
J.-O. Nilsson, P. Kangas, T.
Karlsson and A. Wilson, Metall.
Mater. Trans. A 31A, (2000), 35.
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