Abstract
The nucleation entropy expression for binary alloys is extended to the n-component system for regular solution behaviour. In general, the nucleation entropy increases with the number of components comprising the system. A method is illustrated for determining the nucleation entropy of intermediate compounds or phases of limited solubility when the formation entropy is known, and the nucleation entropies of TiAl3 and TiAI2.4Si0.6 for the Al-Ti and the Al-Ti-Si systems are calculated. It is shown that the Si-enhanced grain refinement effect in Al-Ti alloys is in agreement with the higher nucleation entropy and corresponding nucleation rate for the ternary system.