Direct observations of dislocation substructures formed by nano-indentation of the α-phase in an α/β titanium alloy

Nano-indentation has been used to assess the hardness of equiaxed grains of α-Ti as a function of orientation. Surface normals of these grains in metallographic sections were assessed using orientation imaging microscopy. Thin membranes of material from below a series of nano-indentations were excised by use of a dual-beam focused ion beam instrument. In this way, the dislocation substructures beneath individual indentations were characterized using transmission electron microscopy, permitting an identification of both statistically stored and geometrically necessary dislocations.