Major advances have been made over the past 30 years in the development of an integrated computational materials design (ICMD) technology. The hierarchical structure of its methods, tools, and supporting fundamental materials databases is reviewed here, with an emphasis on successful applications of CALPHAD (calculation of phase diagrams)-based tools as an example of ICMD, expressing mechanistic understanding in quantitative form to support science-based materials engineering. Opportunities are identified for rapid expansion of CALPHAD databases, as well as a major restructuring of materials education.

The microstructure of the Ni-based superalloy IN100 processed by a powder metallurgy route was evaluated to reveal the structures, volume fractions, distributions, and chemistries of the various phases present. These data were compared with those predicted by computational thermodynamics. It is shown that the microstructural parameters expected on the basis of global equilibrium conditions differ significantly from those measured experimentally. However, modification of these calculations by use of constrained and successive equilibria compensated for kinetic effects and led to accurate (or better) predictions of phase volume fractions and chemistries in this alloy. This demonstrated that such modified phase equilibria calculations could be powerful tools for modeling microstructures, even in complex multicomponent alloys processed under nonequilibrium conditions.

Nucleation temperatures are calculated for the case of solidification in atomized metal droplets where spherical substrate particles act as nucleation catalysts. Following the method of Fletcher, the effect of substrate size on catalytic potency is illustrated, and the model is applied to the nucleation of bcc solid from pure, liquid iron containing oxide substrate particles as catalysts. Supercooling data from the literature are used to determine wetting angles for alumina, silica, and rare-earth oxide. Oxide particle-size distributions are then used to predict the supercooling behavior of atomized liquid droplets based on the probability that a given size of droplet will contain a particular size of substrate particle. A transition size regime is found separating droplet sizes undergoing very small and very large supercoolings, respectively. This is discussed in terms of the types and number densities of inclusions present during atomization of the melt.