APPLICATIONS OF THERMO-CALC

Titanium and TiAl

Thermo-Calc can be used to predict thermophysical and phase-based properties as well as to simulate material behavior throughout the materials life cycle for a wide range of Ti and TiAl alloys.

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Applications for Titanium / TiAl Alloys

For applications requiring good corrosion resistance, high temperature specific strength, and toughness, titanium and titanium aluminide alloys are commonly used. The properties of these alloys are very sensitive to the variation in chemistry, especially oxygen, which can be difficult to capture for multicomponent alloys. Titanium alloy properties also strongly depend on thermo-mechanical processing around the beta transus temperature, which is also sensitive to chemistry.

Experiments and handbook data cannot take into account all possible variations in chemistry and processing conditions. Thermo-Calc can simulate these effects to fill in data gaps and make predictions of material behavior throughout the materials life cycle.

Calculate the following based on your actual alloy chemistry:

Thermophysical properties:

Specific heat, enthalpy, latent heat, density as a function of temperature, and coefficients of thermal expansion
Phase-based properties:

Critical transformation temperatures such as β transus, α transus, α2+γ eutectoid, and α/β T₀ line

Solvus temperatures and volume fractions of phases such as Laves phase, α2-Ti3Al, B2, and Ti5Si3

Partitioning of alloying elements between α and β, solubility limits, and phase diagrams

Hardness/Yield strength. Learn more at the Titanium Model Library page.
Elastic properties:

Elastic moduli (bulk modulus, shear modulus, and Young’s modulus) for BCC, HCP, and FCC phases

Elastic constants (C11, C12, C13, C33, and C44) for BCC, HCP, and FCC phases
Equilibrium and non-equilibrium solidification:

Liquidus, solidus, incipient melt temperatures, freezing range, fraction solid curves, solidification path, fraction eutectic, microsegregation, partition coefficients, latent heat, shrinkage, and more
Homogenization:

Optimal homogenization temperatures, time needed to homogenize any chemical segregation arising from solidification, and/or dissolve precipitates
Precipitation hardening:

Concurrent nucleation, growth/dissolution, coarsening of precipitate phases, volume fraction, and size distribution as a function of time
Surface hardening:

Nitriding kinetics of Ti alloys
Martensitic transformations. Learn more at the Titanium Model Library page.

Properties that Can Be Calculated with Thermo-Calc

Application Examples

Thermo-Calc has many applications to Ti- and TiAl-based alloys. Below are three such examples.

Calculate Beta Approach Curves

The β-transus temperature in titanium alloys plays an important role in the design of thermo-mechanical treatments. It primarily depends on the chemical composition of the alloy and is sensitive to the actual alloy chemistry. The oxygen content also has a big effect on the stability of the alpha phase. A beta approach curve shows the fraction of beta phase as a function of temperature and is useful when designing heat treatments to obtain specific properties.

This figure shows a beta approach curve for a Ti-6-2-4-2 alloy calculated in Thermo-Calc along with experimental data from Semiatin et al., Metall. Mater. Trans. A, vol. 38, no. 4, pp. 910–921, 2007.

Predict Phase Balance as a Function of Cooling Rate

There is an inherent relationship between the material microstructure and the final material properties of a component. In titanium alloys, the balance of alpha/beta phases plays a major role in determining the final mechanical, corrosion, and creep properties. This phase balance can vary as a function of cooling rate. Thermo-Calc can simulate phase balance and precipitation behavior as a function of thermal history.

This figure shows the simulated amount of alpha phase in Ti-6Al-4V alloys as a function of cooling rate from 950 °C using the Diffusion Module (DICTRA) (recalculated based on data from Martukanitz et al., Addit. Manuf., vol. 1–4, pp. 52–63, 2014). The final amount of alpha is reduced as the cooling rate is increased.

A plot showing the phase balance in Ti-6Al-4V as a function of different cooling rates.

Calculate Bulk and Young’s Modulus as a Function of Composition

Ti-alloys are a popular choice for biomedical implants due to their high yield strength, good ductility, corrosion resistance, and biocompatibility. However, the Young’s modulus mismatch between Ti- (>100 GPa) and human cortical bone (10-32 GPa) can lead to implant failure, thus making them difficult to use.

Thermo-Calc’s Titanium Databases have modelled elastic properties of Ti-alloys, which can be plotted as a function of composition and temperature, thus helping to predict Ti-alloy behavior conducive for biomedical applications. The example here is from Alberta et al., 2023, wherein the Young’s and Bulk modulus of a Ti-45Nb-xGa BCC β Ti-alloy is shown. Ga, one of the elements in the TCTI Database, is important because it is considered to lower the overall Young’s modulus and have potential bactericidal activity.