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.

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). 

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.

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. 

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.

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.

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.

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