2. ThermoCalc Scripts

ThermoCalc software contains both a windows version which is a typical user interface, and a classical console version which requires input of subsequent command-line inputs. The console version will be primarily discussed in this document as it will be used later as a subroutine in the executable module to output the equilbrium of the compositional matrix array used for chemistry optimization. The console version is separated into multiple modules for first initializing the system, setting conditions for the equilibrium, running either a stepping routine (1-dimenional) for computing property diagrams or mapping routines (2-4 dimensional) for computing phase diagrams, and finally a graphing module. A flow chart of each of the modules along with their associated commands is outlined in Figure 1.

Fig. 1: Flow chart of the set of the modules for calculating phase diagrams with the console version of ThermoCalc. The bolded text in each box are the associated commandeds to enter into each module

Typically you will want to create a new file in the computers directory for every equilibrium calculation you are going to run. Inside this folder copy a shortcut to the ThermoCalc classic executable. When you enter the shortcut any files that will be saved will be saved in that directory. Upon entering the console version the first step is to save every command you input in the console into a log file. The command s-l-f, or set-log-file will create a .log file in directory that the ThermoCalc shortcut is with the filename specified in the following argument. The next line is the heading information to describe what the following file will do.

s-l-f filename  @@set log file 
Calculate isopleth of 2032Nb system @@heading for the .log file
					

The next step is to go into the appropriate initialization module. For equilibrium calculations most of the time you will use the data module to first initialize the system. The data module gives the most amount of freedom to set the specific criteria on the system, however there is a simplified module that will ask the user questions to specify the parameters for the system. The simplified module is accessed by first going into the poly-3 module by typing the command “go p-3”, and then typing “def-mat”. For the purposes of this script we will need to suspend certain constituents in the G-phase sublattice module so the data module should be used. The last thing to note is that if the user wants to perform Scheil calculations, the module command is simply “go scheil” it is set up the same way as the “def-mat” module where it will ask you a series up questions to set up the parameters.

The default database ThermoCalc will draw from is the TCFE* database, TCS Steels/Fe-alloys database. The version used in this document is version 6, and does not contain G-phase; however version 7 has recently been released and does now contain G-phase. The TTNI8 database, TT Ni-based superalloys database, was appended to the system to include G-phase in the system. It should be noted that the TT databases do not contain volumetic data whereas, the TC databases do. Therefore volumetric parameters will have to be calculated in a post process if the data is imported from a TT database.

The first step is to specify the components in the system and then import the appropriate phases for both the TCFE6 database, and the TTNI8 database. The rej P * command on line 5 rejects all the phases in the database, where the * is a wild card term meaning all. If the user does not know what phases should be present in the system, the lines 5 and 6 can be omitted an a generic run can be performed. It is necessary to specify the phases in the system, as sometimes phases that are not present in any literature on the alloy will be stable in the equilibrium calculation, which then cannot be verified. In the TCFE6 database every phase specified for the system should be restored in line 6. Be sure to input the get command after to pull the relevant information from the database. To reject certain constituents of a phase the command rej c < phase > < sublattice > can be input, where the user will then be prompted for which element they would like to reject. This operation can also be done in the windows version of ThermoCalc.

go data
def-ele Fe Cr Ni Si Nb C Mn N Mo
rej P *
res P FCC_A1 M7C3 M23C6 M6C MC Liq Z-Phase
get
app TTNI8
def-ele Fe Cr Ni Si Nb C Mn Ti Mo
rej P *
res P G_Phase
rej c g-phase 1
fe

rej c g-phase 3
Cr

rej c g-phase 3
Mn

get

After the system has been initialized it is time to set up the conditions for equilibrium. The command s-c is short for set-condition, where the intensive properties such as temperature, and pressure, and extensive properties such as the size of the system (e.g. n = 1mol), and the composition (x_i) need to be defined. Temperature is in kelvin, and composition is defined as weight fraction w(element), or mole fraction x(element). Weight fractions should be input for all but one of the components, which will be the dependent variables. This will make sure that the sum of the weight fractions is equal to unity. The command c-e calculates the equilibrium, while l-e lists the equilibrium either on screen or in this case to a file eq.txt. The conditions set will be the initial equilibrium calculated, and does not hold any relevance over the subsequent mapping or stepping functions. Next, is to map the phase diagram over the set axis variable limits. s-a-v 1 t sets the y-axis to temperature with a range between 400-1800K, and s-a-v 2 w(N) sets the x-axis to the weight fraction of nitrogen. The map command will initiate the mapping procedure.

go p-3
s-c t=1089 n=1 p=101325
s-c w(Cr)=0.19 w(Ni)=0.31 w(Si)=0.005

c-e
l-e
eq.txt
VWCS
s-a-v 1 t 410 1800 27.8
s-a-v 2 w(N) 0 0.3 0.001
map

Alternatively, to produce property diagrams (dependent vs. independent variables) only the first axis will need to be specified, followed by the step command. ThermoCalc will initiate its global minimization procedure, and incrementally step along the axis between the set boundaries. Stepping is a much faster operation than mapping and should be considered depending on what type of information needs to be analyzed. There are numerous options for the stepping function, but in this case the default NORMAL command was chosen. More information about these options can be read in the ThermoCalc TCC user manual supplied with the software package.

s-a-v 1 t 410 1800 27.8
step @@ an alternative to the mapping procedure
NORMAL

After the mapping or stepping functions have completed, the user should proceed to the post module for producing phase, and property diagrams. For the mapping command the default diagram contains both of the variable axis set prior to mapping. For stepping the default property diagram sets the y-axis to the molar phase fraction of each stable phase in the system over variable axis set above. The s-d-a command stands for ‘set-diagram-axis’ where in the case of line 35, the x-axis is being changed to display the temperature in Celsius. The s-s command stand for ‘set-scaling-status’, and can be used to set the axis maximum and minimum values. The plot will show the resulting diagram in a separate window. It is important to know the composition of each of the phases after stepping or mapping procedures, where the constituents that occupy each sublattice, and their site fractions can be determined. The composition of a phase can be determined by changing the y-axis to represent the mole fraction of a phase, where the wild card represents every component in the phase. Lastly, to export the data of a property diagram, the l-d-t command will export the data either to text or to excel. Note that the extension on the excel output is .xls, and not .xlsx.

post
s-d-a x t-c
s-s y n 0 0.1
plot
s-d-a y x(FCC_A1#1,*)
*
plot
FCC_A1#1.ps
l-d-t
FCC_A1#1.xls

After the program is exited, the .log file can be accessed, and will contain all of the commands inpute during the ThermoCalc session. To run the .log file through ThermoCalc, change the extension on the file from .log to .tcm.