Deformation of PST crystals of a TiAl/Ti 3Al two-phase alloy at 1000°C

Abstract

Polysynthetically twinned (PST) crystals of a TiAl(γ)/Ti 3Al(α 2) two-phase alloy (Ti–49.3 at% Al) with three different loading axis orientations were deformed in compression and tension at 1000°C and the deformation behavior and deformation modes in the γ and α 2 phases were investigated. The majority of dislocations observed in all six orientation variants in the γ phase were those with b= 1 2 <110] which often form dislocation networks or sub-boundaries. In addition to these ordinary dislocations, dislocations with b= 1 2 <112], [001] and <101] and twins on one or two 111 <112] systems were observed depending on orientation variant. However, <101] superlattice dislocations and deformation twins were observed much less frequently at 1000°C than at temperatures lower than 800°C. Ordinary dislocations were observed even in γ domains where the loading axis is parallel or perpendicular to the direction of their Burgers vector, indicating that they were generated from dislocation sources as well as through dislocation reactions. In α 2 lamellae, 1 6 <11 2 ̄ 0> dislocations as well as [0001] dislocations were observed for all loading axis orientations.