Strain-assisted formation of nano-scaled lamellar structure in Ti-39at%AI single crystals

We have studied the effects of straining prior to annealing for lamellar structure formation in a Ti-39at%Al single crystal intending to accelerate the lamellar structure formation and decrease the resultant lamellar spacing via preferential nucleation of γ-TiAl phase at dislocations in α2-Ti ₃A phase. In a crystal cold-rolled to 10% reduction before annealing, a fine lamellar structure with 88 nm average spacing was formed by annealing at 1073 K for 1 x 10 ₄ whereas no lamella were observed in the crystal subjected to the same annealing after 5%-cold-rolling. In addition, it was also demonstrated that when the crystal is locally strained by indentation and annealed at 1073 K for 1 xlO ₄ s, a lamellar structure with 43 nm average lamellar spacing is formed in areas near the indentation and there were no lamella beyond these areas.