Atomic insights into the distinctions between {101¯1} twin boundaries and [112¯0]/60° boundaries in additively manufactured Ti-6Al-4V

Abstract

Subtle variations in interface structures significantly influence materials’ mechanical performance. In additively manufactured Ti-6Al-4V alloy, two dominant interfaces, i.e., Type 2 [11$\overline{2}$0]/60° grain boundaries (GBs) and {10$\overline{1}$1}<10$\overline{1}\overline{2}$> ([11$\overline{2}$0]/57.2°) twin boundaries (TBs), share the same rotation axis with a slight ∼2.8° misorientation discrepancy. However, their precise atomic structural disparities remain unclear, hampering comprehension of their mechanical response and microstructure optimization. This study conducts an atomic-scale investigation on these two interfaces in additively manufactured Ti-6Al-4V alloy, revealing that {10$\overline{1}$1} TBs mainly consist of coherent TBs adorned with dispersed glissile twinning dislocations. In contrast, Type 2 [11$\overline{2}$0]/60° GBs exhibit serrated features with periodic arrays of immobile disconnections containing misfit dislocations. These misfit dislocations, comprising 〈a₆₀〉 dislocations, help accommodate the ∼2.8° inclination between {10$\overline{1}$1} planes of adjacent α (or α′) variants that form Type 2 [11$\overline{2}$0]/60° GBs. These findings offer atomic-scale insights into the structural design of additively manufactured dual-phase titanium alloys.