Knowledge of phase equilibria and phase transformations is absolutely essential for the development of new materials and processing methods. The CALPHAD (CALculation of PHAse Diagrams) method is a proven, indispensable tool in this endeavor. It combines thermodynamic descriptions of binary and ternary systems to predict phase equilibria and phase transformation temperatures in multicomponent systems. Further, thermodynamic calculations can be coupled with diffusion mobility descriptions for the simulation of diffusion induced phase transformations.
For materials and process developers, the knowledge of the uncertainty associated with the results from CALPHAD is crucial. Currently, however, the reliability of these predictions is inferred by comparing CALPHAD results to experimental phase equilibria data of commercial alloys. This limits the region of confidence to known composition and temperature regimes. Isolated attempts at evaluating confidence intervals for unary self-diffusion data and binary phase diagrams have been made, but no attempt has been made to evaluate uncertainties that originate from the descriptions of the unary, binary and ternary systems that constitute a multicomponent system.