In the 100th Column of the Heat Treat Doctor, published in Industrial Heating magazine, Dan Herring states that heat treating can best be defined as “the controlled application of time, temperature and atmosphere to produce a predictable change in the internal structure (i.e. the microstructure) of a material.” Historically such predictions were based on experience, instinct and empirical models. Thermo-Calc Software’s products, such as Thermo-Calc, DICTRA and TC-PRISMA, allow such predictions to be made based on a scientific approach for a range of heat treat related applications.

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Reliable Simulation of Heat Treating Using CALPHAD-Based Tools


  • Calculate furnace gas chemistry based on composition, temperature and pressure, along with activity coefficients (such as activity of carbon, nitrogen, etc.) in the gas.
  • Predict formation of precipitate phases within an alloy as a function of composition and temperature, along with the amounts of those phases and their compositions.
  • Plot multicomponent phase diagrams, including Lehrer diagrams, for alloys that allow a quick overview of optimal regions for a heat treat process.

Diffusion module (DICTRA)

  • Simulate the diffusion of carbon, nitrogen and boron in multicomponent alloys and predict the case depth profile, for example, as a function of time and carbon activity or carbon flux at the surface.
  • Model the growth, coarsening and dissolution of precipitates (such as carbides in steels or Al2Cu in Al alloys).
  • Predict the homogenisation of multi-component, multi-phase alloys including Ni superalloys.  
  • Model post weld heat treatment.

Precipitation module (TC-PRISMA) 

  • Simulate the concurrent nucleation, growth, dissolution and coarsening of precipitate phases as a function of alloy chemistry, temperature and time, during an isothermal / non-isothermal heat-treat cycle.
  • Predict the fraction of precipitate phases and the number density and size distribution of the precipitates.
  • Calculate TTT diagrams for precipitate phases.