Strain-assisted Formation of Nano-scaled Lamellar Structure in Ti-39at%Al Single Crystals

Abstract

ABSTRACTWe 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-Ti3Al 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 1×104 s whereas no lamella were observed in the crystal subjected to the same annealing without cold-rolling. In addition, it was also demonstrated that when the crystal is locally strained by indentation and annealed at 1073 K for 1×104 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. This means that distributions of lamellae can be controlled by controlling the distribution of strain before annealing.