Vibration-Enhanced Hot Workability of TiAl Alloy Induced by the Motion of 1/2<112] Superdislocations

Abstract

The limited hot workability of TiAl alloys significantly restricts their widespread application. This paper proposes an economical approach to enhance their formability through vibration-assisted forming. By applying low-frequency vibration at 1.5 Hz during a vibration-assisted tensile test (VT), the elongation of the as-cast TiAl alloy increased to 82%, nearly 110% higher than the 39% observed in a normal tensile test (NT). TEM observations indicate that, under vibration conditions, the primary deformation mechanisms of the TiAl alloy shifted from 1/2<110] ordinary dislocation glide to 1/2<112] superdislocations glide and twinning. Additionally, 1/2<112] superdislocations were observed directly crossing the α2/γ phase interface. It was revealed that vibration promoted the massive activation of 1/2<112] superdislocations and the formation of twins, facilitating the cross-slip of 1/2<112] superdislocations and their escape of external particle pinning, thus allowing the material to accommodate higher plastic strains and achieve a greater proportion of recrystallized grains. Our study has uncovered a new mechanism of plastic deformation in TiAl alloys induced by vibration, offering a novel solution to the challenges of thermoplastic forming of these alloys.

Keywords: TiAl alloy, superdislocation, cross-slip, DRX, twins