Nucleation entropy and grain refinement of alloys

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 TiAI_2.4Si_0.6 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.