Solute Redistribution, Liquid/Solid Interface Instability, and Initial Transient Regions during the Unidirectional Solidification of Ti-6-4 and Ti-17 Alloys

The importance of investigating solute redistribution during the unidirectional solidification of multi-component alloys is broadly discussed in the literature. A previously developed analytical model that was experimentally validated for Al-Cu, Sn-Bi and Fe-Si dilute binary alloy systems is used in this article to study in detail the solute redistribution, the liquid/solid interface stability based on an extended transient constitutional undercooling criterion and the size of the initial transient region during the unidirectional solidification of Ti-6-4 and Ti-17 alloys. A comparison between Ti-6-4 and Ti-17 alloy systems with respect to interface stability and the size of the initial transient region is also provided. The effective partition coefficients of the alloying elements in these alloys were determined based on specially designed experimental measurements.