Effects of boron on microstructure in cast titanium alloys

Abstract

Trace additions of boron to commercial purity titanium result in significant microstructural changes. Changes include the promotion of dendritic growth and refinement in both the prior-β and α-grain size. Boron partitions strongly on solidification and TiB intermetallics are observed throughout the microstructure, confined to interdendritic regions. This strong partitioning of solute causes prior-β grain refinement, and the presence of TiB intermetallics and/or the increased β-grain boundary surface area associated with the change in β-grain morphology assists nucleation of the α-phase.