Crack Susceptibility Coefficient Property Model Settings

The Crack Susceptibility Coefficient Property Model calculates the hot tearing tendency during solidification.

This General Model is available when using the Property Model Calculator in Thermo‑Calc.

When the default Clyne and Davies is selected as the CSC Model, the calculations use Scheil and assumptions of cooling rates under three different thermal conditions:

  • Constant cooling rate, dT/dt = constant
  • Constant heat flow, dQ/dt = constant
  • Heat flow proportional to 1/sqrt(time)

For details about this more advanced model, see About the Crack Susceptibility Coefficient Property Model.

For an example, see PM_G_07: Hot Crack Susceptibility.

Configuration Settings

These settings are found on the Property Model Calculator when Crack Susceptibility Coefficient is selected under General Models.

When working in the Configuration window, click the Description tab for more information about the Model.

For the details about the Condition Definitions, Calculation Type, Timeout in minutes, Parallel Calculation, and other calculation associated settings, see Property Model Calculator: Configuration Window Settings.

Scheil Parameters

These parameters are the same as those used for the Scheil Calculator although some setting names are slightly different.

The advanced Scheil settings are described with Scheil Advanced Options: Property Models.

Enter a Scheil start temperature for the Scheil simulation that is higher than the liquidus temperature of the alloy. Is given in the same unit as the temperature in the Condition Definitions.

Click to select a Calculation type: Classic Scheil, Scheil with back diffusion in primary phase, or Scheil with solute trapping. Then based on this selection, additional settings are made available as indicated.

Enter the element/component to make as Fast diffusers. Include a space between each entry, C N, for example, is the default entered for Carbon and Nitrogen to be fast diffusers.

Select the Allow delta ferrite to austenite transition in steel checkbox to enable BCC to FCC transition.

This feature should only be used for such steels for which it is reasonable to assume infinitely fast diffusion (equilibrium conditions) when delta ferrite is present. When the Allow delta ferrite to austenite transition in steel checkbox is selected in Graphical Mode or the DELTA_FERRITE_AUSTENITE_TRANSITION command used in Console Mode, this essentially assumes that diffusion can be considered (infinitely) fast when delta ferrite is present as a solid phase, i.e assumes an equilibrium condition. After delta ferrite is no longer stable, the usual Scheil assumptions for the selected calculation type are in effect. This setting is therefore not suitable for steels where you DO NOT have a complete BCC to FCC transition during solidification. This setting is also NOT available in combination with solute trapping.

Click the Show advanced Scheil options checkbox to enter several settings related to Scheil calculations. See Scheil Advanced Options: Property Models.

CSC Model Selection

Choose a CSC Model: Clyne and Davies (the default), Kou, or Easton.

Then continue with these additional settings:

For details and references about these models, see About the Crack Susceptibility Coefficient Property Model.

Additional Scheil Calculation Type Settings

This field is available when Scheil with back diffusion in primary phase is selected.

Specify the Cooling rate in Kelvin per second (K/s). An increased value moves the result from equilibrium toward a Scheil-Gulliver calculation.

This field is available when Scheil with back diffusion in primary phase is selected.

The Secondary dendrite arm spacing is the distance in meters between two secondary dendrite arms. It is calculated from the cooling rate as c*(cooling rate)-n where c and n are entered in these fields.

Enter values for Secondary dendrite arm spacing c and Secondary dendrite arm spacing n.

This field is available when Scheil with back diffusion in primary phase or Scheil with solute trapping is selected.

The primary solidified phase is the phase where the back diffusion or solute trapping takes place.

If Automatic (Scheil Calculator) or Any phase (Property Models) is selected (or kept as the default), the program tries to find the phase which gives the most back diffusion or solute trapping.

To override this setting, choose a specific primary phase from the list:

  • For back diffusion, only phases with diffusion data can be used as primary phases.
  • For solute trapping, only phases that dissolve all elements in the system can be used as primary phases.

These fields are available when Scheil with solute trapping is selected.

As needed, enter Scanning speed and α to define the Calculated solidification speed.

On the Scheil Calculator, the Calculated solidification speed is shown. For Property Models, below is how the values are calculated from the Scanning speed and α values entered.

The Calculated Solidification Speed is Vs = Vscanning * cos(α) m/s, where Vscanning is the user specified Scanning speed in m/s and α is the alpha angle, α, between the solid/liquid boundary and scanning direction.

Thermal Mode and Liquid Fraction Parameters (Clyne and Davies)

These settings are available when Clyne and Davies is selected as the CSC Model.

Select a Thermal mode for the solidification simulation:

  • Constant cooling rate, dT/dt = constant
  • Constant heat flow, dQ/dt = constant
  • Heat flow proportional to 1/sqrt(time) (i.e. heat flow is proportional to Heat flow prop 1/sqrt(time) )

Enter a value for the Liquid fraction for start of relaxation.

Enter a value for the Liquid fraction transition to vulnerability.

Enter a value for the Liquid fraction smallest to vulnerability.

Solid Fraction for Coherency and Solid Fraction for Coalescence (Easton)

These settings are available when Easton is selected as the CSC Model.

Enter a value in the Solid fraction for coherency field, which is the solid fraction for a coherent dendrite structure. The default is 0.7.

Enter a value in the Solid fraction for coalescence field, which is the solid fraction for coalescence of a dendrite structure. The default is 0.98.

Plot Renderer Settings

Plot Renderer and Plot Renderer: Configuration Settings

When setting up your calculation on the Plot Renderer and/or Table Renderer, the following axis variables are available for the conditions defined on the Property Model Calculator.

When selecting quantities on the Plot Renderer or Table Renderer, the quantity names include an abbreviated name for the Property Model it is associated to. This is useful in particular when you are calculating two or more Property Models that share names for the quantities. The short name identifying the specific Property Model is included in parentheses after the name of the quantity. Below are the full and abbreviated names for each Property Model.

For a list of the abbreviations associated to a Property Model, see Result Quantities: Property Model Abbreviations.

Select from these plot quantities:

  • Composition
  • Crack Susceptibility coefficient. The tendency for the material to crack during solidification.
  • Liquidus temperature
  • Solidus temperature
  • Freezing range [K]. The solidification freezing range (Liquidus - Solidus) given in Kelvin.