Thermo-Calc 2021a Release Overview

Thermo-Calc 2021a is released in December 2020 with 16 new and updated databases, a Property Model for Bainite, a Property Model for Crack Susceptibility, improvements to the Process Metallurgy Module, and much more.

Highlights of Thermo-Calc 2021a

New Bainite Model

Thermo-Calc 2021a introduces a Bainite Model for the Steel Model Library. The Bainite Model describes the thermodynamics and isothermal kinetics of bainite transformation from austenite. This Model can calculate bainite start temperature, transformation times, bainite plate lengthening rate, and phase constitution at the final state. 

A TTT diagram which shows the calculated start (2%), half (50%), and finish (98%) curves of bainite as compared to the experimentally measured 1% transformation times, calculated using the new Bainite Model. The alloy is a hypereutectoid steel with the composition Fe-0.97C-0.72Mn-0.32Si-1.54Ni-0.8Cr-0.26Mo (mass %).


This release includes one new example to help users get started working with the new Bainite Model, PM_Fe_05_Fe-C-Mn-Si-Ni-Cr-Mo_Bainite.tcu

To learn more about the new Bainite Model, visit the Steel Model Library page or refer to the Thermo-Calc Documentation set (search for Bainite in the PDF). 

Five New Property Models

This release includes five new Property Models, in addition to the new Bainite Model. Each of the Models includes an example demonstrating how to use the Model.

Crack Susceptibility Coefficient Model

The Crack Susceptibility Coefficient Property Model is used to calculate the hot tearing tendency during solidification. Hot tearing is one of the most common and serious defects encountered during the casting of aluminum and magnesium alloys, and this model can help users choose the right alloy composition to reduce the occurrence of this issue.

Example PM_G_07_Hot Crack Susceptibility demonstrates how to set up the model, and an accompanying video discusses how to set up and use the Model. 

T-Zero Temperature Model

The T0 Temperature model calculates the so-called T0 line. The T0 temperature is defined as the temperature where two phases of identical chemical compositions have the same molar Gibbs free energy. This temperature is an important quantity in the field of diffusionless phase transformations, such as martensitic transformation, since it is the upper limit where diffusionless phase transformations can occur. It is also important for processes such as CVD and PVD (chemical and physical vapour deposition), where partitioning typically does not occur and the phase with the lowest Gibbs energy is deposited.

Example PM_G_09_T-Zero Temperature demonstrates this new model.

Spinodal Model

The Spinodal Property Model calculates the spinodal line. The spinodal is defined by the condition where the second derivative of Gibbs free energy is zero (d2G/dx2 = 0). The locus of these points is known as the spinodal curve. Inside the spinodal phase, separation is spontaneous (i.e. does not require nucleation and growth) as any fluctuation in composition results in a lowering of the Gibbs free energy. Phase separation proceeds by amplification of these fluctuations.

Example PM_G_08_Spinodal demonstrates this new model.

Equilibrium with Freeze-in Temperature

The Equilibrium with Freeze-in Temperature Property Model calculates equilibrium at the freeze-in temperature and evaluates the properties at a different temperature. The model can evaluate several properties such as electrical and thermal resistivity / conductivity, density, coefficient of thermal expansion, and others.

Two examples are included in this release demonstrating the new model: PM_G_10_Freeze in Thermal Conductivity and PM_G_11: Freeze in Electric Conductivity.

Critical Transformation Temperature for Steels

The Critical Transformation Temperature model is used to calculate critical transformation temperatures for steels. It can output the common transformation temperature for steels , including liquidus, solidus, A0, A1, and more. This new model is specific to steels and requires a license for the Steel Model Library.

Example PM_FE_04_Critical Temperature demonstrates this new model.

New Framework for Developing Property Models

Thermo-Calc 2021a introduces a new way for users to develop Property Models using TC-Python. Previously, users could develop Property Models using a Jython-based API called the Property Model Development Framework, but Jython is no longer being supported, so we are introducing a new framework with significantly improved features. 

This new framework allows users to use any python library, such as numpy, scipy, or scikit-learn, within the Property Models, making model development quite powerful. Additionally, this new system allows the Property Models to perform any calculation type that is available in Thermo-Calc. Previously, only single equilibrium calculations were supported

This new feature requires a license for TC-Python. Learn more in the TC-Python help under the Property Model Framework section or in the Property Model Framework Documentation

Process Metallurgy Module Improvements for VOD

The Process Metallurgy Module for steel and slag now allows users to change the pressure and reaction kinetics in the process schedule, valuable features for vacuum degassing processes.


A screenshot of the Process Metallurgy Module showing how users can now easily change the pressure and reaction kinetics in the process schedule. These are valuable new features for VOD processes.

A new example, PMET_07_Vacuum Oxygen Decarburization Kinetics, demonstrates these new features. A companion PDF is available that discusses the example in detail. 

The Process Metallurgy Module includes several other updates, which you can read about in the Release Notes

Diffusion Module (DICTRA) Allows Pausing for Boundary Conditions

Users can now pause Diffusion Module (DICTRA) simulations in the Graphical Mode to change left and right boundary conditions then resume the calculation. This is useful, for example, when you want to simulate carburization because it is common to first have a step with high carbon activity in the furnace for the actual carburization and then lower it and allow the carbon in the specimen to diffuse without further increased carbon content.


The Diffusion Module (DICTRA) now allows users to pause simulations to change left and right boundary conditions then continue with the calculation. This is especially useful when you want to simulate carburization.

Users can try this new feature by running example D_07_Diffusion_Carburization_Multiphase.tcu, pausing the calculation, changing the boundary conditions, and then resuming the calculation. 

New Editor for User-Developed Databases

For advanced users who develop their own databases, a new database editing tool is introduced in Thermo-Calc 2021a, the TDB Editor. This tool speeds up the database editing process by providing immediate feedback through syntax coloring (1), syntax checking (2), and by allowing formatting (3) and easy navigation to items of interest in the TDB file.


A screenshot of the new database editing program, the TDB Editor, which allows for easier editing of user-developed databases through syntax coloring (1), syntax checking (2), and by allowing formatting (3) and easy navigation to items of interest in the TDB file.

This new editor is available for free as part of the Thermo-Calc 2021a release, but it requires additional, open source programs to run. The editor is currently only supported on Windows and Linux platforms, not on Mac.

To learn more about the TDB editor, refer to the Release Notes.

Sixteen New and Updated Databases

The 2021a release includes nine new and seven updated databases, as described below.

TCMG6 Magnesium-based Alloys Database

  • Five thermophysical properties are added: electrical resistivity, thermal conductivity, viscosity of liquid, surface tension of liquid, molar volume
  • Hydrogen and bismuth are added 
  • 12 new binary systems are assessed
  • 11 new ternary systems are assessed
  • The metastable precipitates Mg7R, Mg3R (D03), Mg3R (D019) that form during aging of Mg-RE (rare earth) alloys have been modeled in the following systems: Mg-Gd, Mg-Nd, Mg-Y
  • Updates to the following phase equilibria: Cu-Gd, Mg-Nd-Zn, Mg-Al-Ce, Mg-Si-Sn

MOBMG2 Magnesium-based Alloys Mobility Database

  • Nine elements are added: Bi, Dy, Er, Ga, H, Ho, In, Sb, and Sm
  • Existing descriptions of the HCP_A3 are improved taking into account the new available experimental data and CALPHAD assessments
  • Updated to correspond to the new TCMG6

TCFE11 Steel and Fe-alloys Database

  • Surface tension of liquid is added
  • Molar volume of liquid is updated
  • Hydrogen is added to the relevant solution phases (Liquid, FCC, BCC, and HCP) and some hydrate phases
  • 37 new binary systems are assessed
  • 20 new ternary systems are assessed
  • And much more...

MOBFE6 Steel and Fe-alloys Mobility Database

  • Hydrogen is added
  • Updated to correspond to the new TCFE11

TCTI3 Titanium and TiAl-alloys Database

  • Two thermophysical properties are added: viscosity of liquid and surface tension of liquid
  • Copper is added
  • 9 new binary systems are assessed
  • 13 new ternary systems are assessed

MOBTI4 Titanium and TiAl-alloys Mobility Database

  • Copper is added to the phases BCC_A2, HCP_A3, and liquid
  • Updated to correspond to the new TCTI3

MOBAL6 Aluminum-based Alloys Mobility Database

  • Nb, P, and Y are added

Mephista-19 Nuclear Fuels Database

  • 10 binary systems are improved
  • 5 pseudo-binary systems are improved
  • 3 ternary systems are improved
  • And much more...

NUCLEA-19 Nuclear Reactor Circumstances Database

  • 26 binary systems are improved
  • 11 pseudo-binary systems are improved
  • 5 ternary systems are improved
  • And much more...

Updated Databases

Seven databases are updated with the 2021a release. Users with the most current version of a database and a valid Maintenance and Support Subscription receive the updated database for free.

  • TCHEA4.2 - High Entropy Alloys Database
  • TCOX10.1 - Metal Oxide Solutions Database
  • SALT1.3 - Molten Salts Database
  • TCAL7.1 - Al-based Alloys Database
  • MOBTI3.1 - Titanium and Titanium Aluminide Mobility Database
  • TCFE8.2 - Steel and Fe-alloys Databases
  • TCFE 9.3 - Steel and Fe-alloys Databases

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