ATOMIC LEVEL OBSERVATIONS OF MECHANICAL DAMAGE IN SHOT PEENED TiAl

摘要

High-resolution transmission microscopy has been used to reveal the defect processes occurring during shot peening of a high strength titanium aluminide alloy with a nearly lamellar microstructure. Deformation is characterized by intensive dislocation glide and mechanical twinning, involving all potential slip systems available in the α_2(Ti_3Al)and y(TiAl)phases. The outermost surface layer consists of extremely fine crystals that are probably a contaminant titanium nitride phase, embedded into an amorphous phase. The mechanisms involved in this mechanically driven solid state transformation will be elucidated.