How to Simulate High-Entropy Alloys (HEAs) in Thermo-Calc : A Step-by-Step Guide

High-Entropy Alloys (HEAs) have revolutionized materials science. By combining five or more principal elements in near-equimolar proportions, researchers are discovering alloys with unprecedented strength, corrosion resistance, and thermal stability.

However, exploring the massive compositional space of HEAs experimentally is incredibly time-consuming and expensive. This is where Computational Thermodynamics (CALPHAD) comes in.

Thermo-Calc is the industry standard for predicting phase equilibria in HEAs. In this guide, we will walk you through how to simulate a classic HEA—the Cantor alloy (CoCrFeMnNi)—using Thermo-Calc, focusing on equilibrium phase diagrams and non-equilibrium Scheil solidification simulations.

Note: This tutorial is based on the Thermo-Calc 2026 graphical interface. If you don’t have the software yet, you can download Thermo-Calc 2026 here.

Why Simulate HEAs in Thermo-Calc?

Before we start, it’s important to understand what Thermo-Calc can and cannot do for HEAs:

• What it does: Accurately predicts which phases (FCC, BCC, sigma, Laves, etc.) will form at specific temperatures and compositions.
• Why HEAs need special databases: You cannot use standard steel or aluminum databases for HEAs. You must use a database specifically assessed for multi-component systems, such as the TCHEA (Thermo-Calc High-Entropy Alloys) database.

Prerequisites

• Thermo-Calc 2026 installed.
• The TCHEA database (TCHEA4 or TCHEA5 are the latest versions).
• Basic understanding of alloy phases.

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Step 1: Start a New Project and Select the Database

1. Open Thermo-Calc 2026.
2. In the start window, select New Equilibrium Calculation (or click “Start” and then “Equilibrium”).
3. The first step is to define your system. Click on the Database button.
4. Navigate to where your HEA databases are stored and select TCHEA5.tdb (or the latest version available to you).
5. Click Open.

Step 2: Define the System Elements

For the Cantor alloy, we need five elements.

1. In the Elements pane, type: Co, Cr, Fe, Mn, Ni.
2. Thermo-Calc will automatically load the relevant phases from the TCHEA database that can form between these five elements (typically liquid, FCC_A1, BCC_A2, HCP_A3, Sigma, etc.).

Step 3: Set the Conditions (Equimolar Composition)

HEAs are defined by their near-equimolar ratios.

1. Go to the Conditions tab.
2. Ensure the System Size is set to 1 (we are calculating in mole fractions/weight fractions, not absolute moles).
3. Set the Temperature to 600 (We will map this later, but we need a starting point).
4. Set the Pressure to 100000 (1 bar).
5. Under composition, set each element to 0.2 (which represents 20 at%, or equimolar for a 5-element system):
   • w(Co)=0.2
   • w(Cr)=0.2
   • w(Fe)=0.2
   • w(Mn)=0.2
   • w(Ni)=0.2

Step 4: Calculate the Equilibrium Phase Fractions

Now let’s find out what phases exist at 600°C.

1. Click the Calculate button (or press F2).
2. Switch to the Results tab. You will see the stable phases at this temperature. For the Cantor alloy at 600°C, you should see a single phase: FCC_A1 with a phase fraction of 1.000.
3. Note: Real Cantor alloys sometimes exhibit minor secondary phases due to kinetic effects, which brings us to the next step.

Step 5: Map a Phase Diagram (Temperature vs. Phase Fraction)

To see the full thermal stability, we need to plot a property diagram.

1. Go to the Plot menu at the top.
2. Select Property Diagram -> Phase Fraction vs. T (Temperature).
3. In the axis settings, set the X-axis (Temperature) to range from 500 to 2000.
4. Thermo-Calc will calculate the phase fractions across this temperature range.
5. Analysis: You will see a single FCC phase line from 500°C up to the liquidus temperature (around 1400°C – 1500°C, depending on the database version). This confirms the Cantor alloy is a single-phase solid solution across a massive temperature range.

Step 6: Perform a Scheil Solidification Simulation (Crucial for HEAs)

Equilibrium calculations assume infinite diffusion in the solid state. In reality, HEAs solidify rapidly, and diffusion in the solid phase is sluggish. This leads to microsegregation. To simulate real casting conditions, you must run a Scheil Simulation.

1. Go to the Functions menu at the top.
2. Select Scheil -> Set Up Scheil Simulation.
3. A new window will appear. Ensure all 5 elements are selected.
4. Set the starting temperature to 2000 (above the liquidus).
5. Set the final solid fraction to stop at 0.99 (99% solid) to prevent the simulation from running infinitely at low temperatures.
6. Click Calculate.
7. Once complete, go to the Plot menu and select Scheil Plot.

Reading the Scheil Results:
Look closely at the Y-axis (Phase Fraction) as the temperature drops. In many HEAs (even those that are single-phase in equilibrium), the Scheil simulation will predict the formation of small amounts of detrimental secondary phases (like the Sigma phase or BCC phase) at the end of solidification due to segregation of elements like Cr or Mn into the interdendritic regions.

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Advanced Tip: High-Throughput Screening with TC-Python

If you want to move away from the Cantor alloy and design your own HEA (e.g., an Al-Co-Cr-Fe-Ni system), clicking through the GUI becomes tedious.

Thermo-Calc 2026 includes TC-Python, a powerful API that allows you to write Python scripts to loop through thousands of compositions automatically. You can write a script that calculates the equilibrium phases for every combination of Al from 0 to 20 at% in 1% increments, outputs the data to a CSV file, and generates a “phase map” to find the exact compositional sweet spot for a single-phase FCC structure.

Conclusion

Simulating High-Entropy Alloys in Thermo-Calc is straightforward once you select the correct database (TCHEA) and understand the difference between equilibrium and Scheil solidification. By mastering these two calculations, you can drastically reduce your experimental trial-and-error and focus only on the most promising HEA compositions.

Ready to get started?

To follow this tutorial, you need the latest tools. Download Thermo-Calc 2026 here to access the newest GUI features, optimized calculation speeds, and the most up-to-date database compatibility.