Effect of high pressure torsion on the microstructure evolution of a gamma Ti–45Al–2Nb–2Mn–0.8 vol% TiB2 alloy

The technique of high pressure torsion (HPT) has been widely used to refine the microstructure of many metallic materials, especially pure metals and disordered alloys. Comparatively fewer studies have, however, been carried out in intermetallics. γ-TiAl alloys are envisioned as high potential materials to replace Ni superalloys in some turbine components due to their good performance at high temperatures and light weight. Exploring the potential beneficial effects of severe plastic deformation techniques in these materials is now timely. In this work, a γ-TiAl alloy with a lamellar microstructure has been processed by HPT using pressures ranging from 1 to 6 GPa and 0 to 5 anvil turns at room temperature. Significant refinement of the microstructure via twin formation, bending of the lamella and the accumulation of a high dislocation density upon the application of shear give rise to a drastic hardness increase.