High strain torsion of a TiAl-based alloy

Abstract

A two-phase lamellar and globular TiAl-based alloy Nb, Ta, B)) with different textures has been deformed in torsion in a Paterson-type rock deformation machine at a temperature of 1173 K under 400 MPa argon confining pressure. The shear stress -shear strain curves with increasing shear strain show a decrease or increase of shear stress in the lamellar and globular case, respectively, to a common steady state value. Activation analysis at high strains yields stress exponents of about 1.8 and an activation energy of 3.29 eV. With increasing shear strain the lamellar structure breaks down and a two-phase fine-grained globular structure develops by recrystallization with a grain size in the order of 2 microns. The weak initial fibre textures at high strains are randomized. The mechanical, microstructural and textural features indicate a transition from dislocation creep to superplastic flow.

Review - Phase Transitions in Ti Alloys Driven by the High Pressure Torsion

“…SPD can also induce various phase transformations. 49) High pressure torsion (HPT) is one of the SPD variants. Many works are devoted to the change in the properties and structure of titanium alloys under the action of HPT (See Table 1).…”

Microstructural evolution of TiAl-based alloys deformed by high-pressure torsion

“…Most of the previous work on HPT of TiAl-based alloys has focused on the texture, recovery and dynamic recrystallization [16,17]; however, information about the microstructure evolution especially phase transformation during torsion deformation of two-phase TiAl-based alloys is still limited. Since shear strain increases within the cylindrical sample from the centre to the edge, changes of microstructure and phase transformations can be studied as a function of shear strain in one sample.…”