Study on the α₂/γ interfacial structures in a two-phase (α₂+γ) alloy deformed at elevated temperature

The details of structure modification on α₂/γ interface induced by deformation in a hot-deformed Ti-45Al-10Nb alloy were investigated by conventional and high-resolution transmission electron microscopy. A new type of dislocation ledge containing 1/3[111] partials was identified. The Burgers vectors of these dislocation ledges were determined to be 1/2[110] or 1/2〈101]. The formation mechanism of this new type of dislocation ledge is discussed. Also, two types of hot deformation induced α₂/γ interfaces, coherent interfaces with high density of ledges and misoriented semi-coherent α₂/γ interfacial boundaries were observed. For the misoriented semi-coherent α₂/γ interfaces, the density of dislocation ledges in these interfaces increases with the misoriented angle between the (111)_γ and (0001)_α2 planes, and 1/3[111] partial dislocations were involved in all the dislocation ledges. The formation mechanism of these deformation-induced α₂/γ interfaces were discussed related to the role of α₂/γ interfaces adjusting the deformation as a dislocation sink absorbing the slipping dislocations in the γ phase. Moreover, misoriented semi-coherent α₂/γ interface related deformation twinning and structure transformation induced by deformation were analyzed and discussed related to the role of α₂/γ interfaces as a dislocation source during deformation.