On the thermal evolution of high-pressure torsion processed titanium aluminide

Abstract

As-received and high-pressure torsion processed Ti-45Al-7.5Nb alloys subjected to in-situ neutron diffraction under ramping temperature reveal microstructural, order parameter, phase and crystallographic evolution. While a high degree of order on the alternating Ti and Al layers on the γ-(0 2 1) planes in as-received material remains thermally unaffected up to 1350 K, severe plastic processing induces atomic disorder, isotropically mixing atoms across all planes. The disorder of the processed material recovers in the temperature range of 660–1000 K, at which regular diffusion dynamics is activated in both specimens. The recovery is seen in all parameters, such as integrated intensity, thermal lattice strain and peak width. Besides this, we attribute the anisotropic disorder in as-received material to different activation of necessary dislocations as regular and super-dislocations and their partials surrounding the stacking faults.