Nanoplastic deformation on Ti-39 at.% Al single crystals for manipulation of every single γ lamella

The effects of nanoscale plastic deformation, produced by nanoimprinting, nanoindentation and nanogrooving, on the formation of periodic dislocation bands in Ti-39 Al (at.%) single crystals were investigated, with a focus on the formation of periodic, parallel basal dislocations. Slip traces of both basal and prism slips were produced on the nanoindented crystal's surface, while only basal slip traces were formed on the surfaces of the nanoimprinted and nanogrooved crystals. A dislocation band, consisting of basal dislocations with relatively high density and non-basal dislocation tangles with exceedingly high density, was produced beneath the nanogrooved trench. However, low-density basal and non-basal dislocations were produced beneath the nanoimprinted indentations. The plastic zones formed were relatively narrow; moreover, non-basal slip traces or dislocations were connected to the basal slip traces and dislocations. The reasons for these formations were examined based on the motion of dislocations affected by antiphase domain boundaries as well as the cross-slip of prism dislocations onto the (0 0 0 1) basal planes. According to the dislocation band characteristics, nanogrooving is the most appropriate of the three processes for producing periodic basal dislocation bands with tunable intervals. Furthermore, a pair of long and thin γ lamellae was formed along the basal plane after annealing of the nanogrooved crystals; they were ∼45 μm deep from the groove with a 500 nm interval, and the thickness of each γ lamella was <100 nm. The results suggest that γ precipitation as a laminated periodic structure can be controlled by nanogrooving-induced plastic deformation.