AM Module Evaporation Prediction in Thermo-Calc 2026b: Composition Change Modeling for Additive Manufacturing

Among the technical additions in Thermo-Calc 2026b, one feature stands out for anyone working in metal additive manufacturing: the Additive Manufacturing (AM) Module can now predict how alloy composition drifts away from specification due to evaporation during printing. This is a genuinely new physics capability, not just a usability improvement — and it’s validated against published experimental data, not just internal benchmarks.

If you’re qualifying AM processes for superalloys, titanium, or aluminum systems where volatile elements are a known risk, this is the most consequential AM Module update in the 2026b release.

The Problem: Why Evaporation Matters in Metal AM

Laser powder-bed fusion (L-PBF) and directed energy deposition (DED) processes generate extremely high local temperatures — often well above the boiling points of volatile alloying elements like aluminum, magnesium, chromium, and molybdenum. When printing parameters (laser power, scan speed, spot size) aren’t properly optimized, these elements can evaporate from the melt pool faster than the bulk composition would suggest.

The consequences compound across a build:

Microstructure deviation from the as-designed alloy
Loss of strength, hardness, and ductility as alloying content drops
Altered tempering response, complicating downstream heat treatment
Reduced corrosion resistance in alloys relying on specific element ratios (e.g., Cr in stainless and superalloy systems)
Cumulative part-to-part inconsistency, a serious problem for process qualification and certification in aerospace and medical applications

Until 2026b, predicting this drift required external experimental characterization or simplified rule-of-thumb corrections. Thermo-Calc’s AM Module now models it directly.

What’s New: “Evaporation with Steady-state” Calculation Type

The core addition is a new calculation type within the AM Module: Evaporation with Steady-state. It’s set up similarly to the existing Transient calculation type, but with default parameters tuned specifically to capture evaporation behavior accurately rather than approximate it.

What it simulates

Multi-track and multi-layer builds — not just a single melt pool pass, but the cumulative effect across an entire printed region
Per-track average composition — output for each individual track as the build progresses
Final-part average composition — the practically relevant number for specification compliance
Evaporated gas composition — what’s actually leaving the melt pool, useful for understanding which elements are most at risk

Where the effect is strongest

The release notes highlight that composition changes are most pronounced when a new powder layer is added — meaning the transition between layers, not just steady continuous printing, is a key driver of cumulative compositional drift. This is a non-obvious detail that’s easy to miss if you’re only thinking about within-track evaporation.

Validation Against Real Experimental Data

What sets this feature apart from a purely theoretical addition is that Thermo-Calc validated it against published experimental results. The release documentation specifically references a comparison with IN939 (a Ni-based superalloy commonly used in gas turbine components) printed at 200W laser power and 1.8 m/s scan speed, benchmarked against data from Mukherjee et al. (2024).

The simulation tracks composition change across 270 tracks, showing:

Large composition shifts occurring specifically at powder-layer transitions
A final track (track 270) composition that represents the practical average for a larger printed part
Reasonable agreement between the calculated final-track composition and the experimentally measured values

For process engineers, this matters because it means the model isn’t just qualitatively plausible — it’s been checked against a real alloy system relevant to high-value AM applications (turbine hardware).

New Visualization and Output Options

Alongside the new calculation type, Thermo-Calc 2026b adds dedicated tools for interpreting evaporation results:

Three new plot quantities in the Plot renderer, covering printed composition and evaporated gas composition
A new Composition History tab specifically for visualizing how composition evolves across tracks and layers
Table export support, so results can be pulled into external reporting or statistical process control workflows

Available in Both GUI and TC-Python

This isn’t a GUI-only feature — the full evaporation modeling capability is also available through TC-Python, which matters if you’re running automated process-window screening or integrating AM simulation into a broader digital-twin or ICME pipeline.

Two new examples ship with 2026b to demonstrate the workflow:

Graphical Mode: AM_16_Composition_Change_Evaporation.tcu
TC-Python: pyex_AM_13_Composition_change.py

Which Alloy Systems Benefit Most

Evaporation risk scales with how volatile the alloying elements are relative to the process temperature. Based on the elements most commonly flagged in AM literature, the systems most likely to see meaningful predictive value from this feature include:

Ni-based superalloys (IN939, IN625, and similar) — Cr and other moderately volatile elements affecting high-temperature performance
Titanium alloys — particularly where Al content drives the α/β phase balance
Aluminum alloys — Mg loss is a well-documented AM challenge, directly affecting strengthening response
High-temperature process routes generally — laser and electron-beam heat sources are explicitly called out as the highest-risk category, since they generate the localized high temperatures where light, volatile elements evaporate most readily

How This Fits Into the Rest of the 2026b Release

The evaporation modeling feature is one piece of a broader set of updates in Thermo-Calc 2026b — alongside the new Property Navigator, 2.2x faster project loading, the renamed and hydrogen-enabled TCNI14 database, and TC-PRISMA precipitation improvements. For the complete rundown of everything shipped in this release, see our full Thermo-Calc 2026b Release: New Features & 9 Databases overview.

💬 Need help figuring out whether your AM Module license tier includes the evaporation calculation type, or want a quote? → Message us on Telegram — free consultation, usually a reply within a few hours.

Licensing and Upgrade Notes

The Evaporation with Steady-state calculation type is part of the standard AM Module — no separate add-on purchase is required if your license already includes the AM Module.
Projects and databases migrate automatically when upgrading an existing installation with a current Maintenance & Support subscription.
If you’re budgeting for a new license, renewal, or AM Module add-on and want an instant cost estimate by version and seat count, use our Thermo-Calc license price calculator.

Conclusion

Evaporation-driven composition drift has long been an acknowledged but hard-to-quantify risk in metal additive manufacturing. Thermo-Calc 2026b’s new Evaporation with Steady-state calculation type gives AM process engineers a way to predict — rather than just suspect — how much an alloy’s composition will shift during a build, validated against real IN939 printing data. For anyone qualifying AM processes for superalloys, titanium, or aluminum parts, this is a capability worth evaluating closely before your next process-window study.

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