Severe Plastic Deformation (SPD) is known to be an effective method of producing
nanocrystalline materials, for instance by HPT and ECAP. These techniques are also capable of
reproducing microstructures which arise naturally when high pressure and friction is involved, for
example in wheel-rail contact problems. The resulting deformation layers build the origin point for
fatigue cracks. For that reason the knowledge of the mechanical properties of these deformation
layers are of vital importance. In the framework of this study a baintic rail steel quality was
deformed by High Pressure Torsion up to distinctive equivalent strains at a nominal pressure of 6
GPa up to a final equivalent strain of 16. Afterwards the evolution of the resulting microstructure
was investigated by Scanning Electron Microscopy, by microhardness measurements and X-ray
diffraction. The bainitic structure showed a strong alignment and fragmentation into the shear
direction with increasing strain, which was accompanied by an increase in hardness as well. X-ray
diffraction measurements showed that the amount of retained austenite decreases dramatically after
small amounts of strain, which indicates that retained austenite cannot be stabilized by high
pressures. Torque measurements during deformation showed after strong hardening at the
beginning, a saturation behaviour for higher strains, whereas for instance pearlitic rail steel qualities
show further hardening.
Elastic plastic deformation of TC6 titanium alloy analyzed by in-situ synchrotron based X-ray diffraction and microstructure based finite element modeling