Processing by high-pressure torsion (HPT) of intermetallics of the Ti-43.2Al-3.98Nb-0.96Mo-0.1B system  leads to  their  grain structure refinement down to the average grain size of 250 nm in 70% of the material’s volume, with the colonies of the gamma and alpha –2-phase lamellae having an interlamellar distance of 100-300 nm retained in the remaining  areas of the material. In UFG intermetallics, an increased microhardness  of 5000 MPa has been revealed, which is 25% higher than that of the initial micro-grained material subjected to isothermal forging (3500 MPa). UFG intermetallics are very interesting as materials operating at elevated temperatures reaching 800С.

 Typical structures in the UFG Ti-43.2Al-3.98Nb-0.96Mo-0.1B intermetallic: (a) areas with an average grain size of 250 nm; (b) areas containing
colonies of the gamma and alpha-2-phases

Properties of the Ti-43.2Al-3.98Nb-0.96Mo-0.1B intermetallic:

State and dimensions of the billetsStructural featuresMicrohardness after HPT processing,MPaMicrohardness after annealing
at a temperature of 800оС, MPa
UFG, diameter 20 mm, thickness 1 mmAverage grain size 250 nm, colonies
of lamellae with an interlamellar
distance of 100-300 nm
Micro-grainedGrains with an average grain size of
30 µm, consisting of alternating
lamellae of the gamma
 and alpha-2-phases

Main publications:

1.  R.K. Islamgaliev, M.A. Nikitina, V.D. Sitdikov. Thermal stability of TiAl-based intermetallic alloys subjected to severe plastic deformation. Intermetallics. (2015) (submitted).
2.  A.N.Tyumentsev, M.V.Tret’yak, Yu.P.Pinzhin, A.D.Korotaev, R.Z.Valiev, R.K.Islamgaliev, A.V.Korznikov. Evolution of defect substructure in the Ni3Al alloy in the course of severe plastic deformation by torsion under pressure. The Physics of Metals and Metalloraphy. 90, 5 (2000) 461-470.
3.  R.K.  Islamgaliev, R.Z.  Valiev, R.S.  Mishra, A.K.  Mukherjee. Enhanced superplastic properties in bulk metastable nanostructured alloys. Mat. Sci. Eng. 304-306 (2001) 206-210