Precipitation Calculator: Options Tab

Select the Preprocess equilibrium data checkbox to calculate the required phase equilibrium properties as a function of temperature for stable and metastable conditions. This speeds up the computation time of non-isothermal simulations or isothermal simulations where there is difficulty with losing precipitate phases during the calculation.

When the checkbox is selected, the stable and meta-stable property diagram data for all simulated precipitate phases is preprocessed. This preprocessing avoids repeating global equilibrium calculations, and speeds up computational time. It also allows for an improved description of precipitate kinetics under severe dissolution conditions. This can occur when temperatures are too high, where the phase is no longer detected in equilibrium calculations, or if the matrix is depleted of precipitate forming species, and the precipitate phase is lost when calculating the driving force.

This feature is used primarily for non-isothermal simulations. For isothermal simulations it can be used when there is difficulty losing precipitate phases during the calculation. In this case, it alters the predicted dissolution kinetics in certain conditions where the precipitation phase is lost and then it also speeds up these calculations.

To use the Include incipient melting checkbox requires that the thermodynamic database (i.e. TCFE, TCNI, and so on) includes the liquid phase. If the liquid phase is not included, then the Perform button is not available (it is grayed out with a message explaining why) until either a liquid phase is included or this checkbox is deselected.

This is available when the Preprocess equilibrium data checkbox is selected.

Select the Include incipient melting checkbox to approximate the melting temperature of precipitate phases. The precipitates are removed upon exceeding this temperature.

Incipient melting is a phenomenon where, due to rapid heating rates, a solid-state precipitate is in solution at temperatures where it would normally dissolve. It liquidates rather than dissolves into the matrix. Being able to include (or exclude) the incipient melting is relevant to simulations involving welding and AM. Including incipient melting in AM calculations is useful to avoid excessive computation time modeling the dissolution of precipitates which would melt. The precipitates are assumed to melt instantaneously upon reaching their incipient melting temperature.

The Max time step fraction is the maximum time step allowed for time integration as fraction of the simulation time. The default is 0.1.

The default number of grid points for every order of magnitude in size space. The default is 150.0.

The maximum allowed number of grid points in size space. The default is 200.0.

The minimum allowed number of grid points in size space. The default is 100.0.

The portion of the volume fraction that can be ignored when determining the time step. The default is 0.01.

The maximum value allowed for relative radius change in one time step. The default is 0.01.

Set a limit on the time step. The default is 0.5.

This defines the maximum absolute (not ratio) change of the volume fraction allowed during one time step. The default is 0.001.

This parameter ensures accuracy for the evolution of effective nucleation rate. The default is 0.5.

Used to place a constraint on how fast the critical radium can vary, and thus put a limit on time step. The default is 0.1.

The cut-off lower limit of precipitate radius. The default is 5.0E-10 m.

The upper limit of the time step that has been enforced in the heating stages. The default is 1.0 s.

Set a limit on the time step by controlling solute depletion or saturation, especially at the isothermal stage. The default is 0.01.