Grain refinement mechanism of boron addition within Ti–Al alloy

To better understand the effects of B addition on the grain refinement mechanism of Ti–Al-based alloys, we investigate liquid local structure, nucleation and liquid/solid interface migration of Ti–Al–B alloy using molecular dynamics with a deep neural network potential. It is found that Ti/Al and B atoms repel each other, and the order structure is decided by Ti–Al bonds in the dilute B solution. B atoms are not involved in the formation of short-range-order structures or the growth of β crystals. The production of borides occurs at the frontier of liquid–solid interface, depending on the presence of a rich-B liquid phase caused by the L → β phase transition. It is indicated that constitutional undercooling causes the grain refinement of Ti–Al-based alloys by B addition.