Investigation of Fe-Al alloys structure after severe plastic deformation.
Severe plastic deformation (SPD) is one of the most effective methods for producing
nanocrystalline or ultrafine-grained metals and alloys. There are several SPD techniques to
synthesize bulk nano- or ultrafine grained metals and alloys, such as equal channel angular
pressing (ECAP) and high-pressure torsion (HPT). In this work, the applicability of the threeaxis plane-strain forging (multi-axial compression MAC) for grain refinement and
improvement in mechanical properties of the Fe3Al intermetallic alloy having a chemical
composition close to Fe-28Al-5Cr-0.8Zr-0.04B was studied. In particular, attention was paid
to the evolution of the microstructure with respect to the effective strain and processing
temperature as well as factors that influence the cracking of the Fe3Al samples. The
specimens having dimensions of 10  10  27 mm were deformed using a MaxStrain system.
The range of the temperature was 20 to 800C with the application up to 80 passes and strain
to   20. The influence of repeated MAC (different number of passes and temperatures) on
the microstructure was investigated in scanning electron microscopy (SEM). Changes in
mechanical properties were measured by tensile and hardness tests and then related to
microstructure development.
On the basis of these studies, forging experiment was carried out on a large laboratoryscale, reproducing the conditions in the Max Strain Gleeble simulator. Samples
5050130 mm were deformed at 800 C temperature from 40% draft per pass, to obtain
strain   2.6. In the material was observed inter alia over 5-fold decrease in grain size.
Also, asymmetric rolling ASR technology creates new possibilities to shape the
structure of Fe-Al alloys. Differentiation of speed rollers leads to shear in surface layer of
workpiece, and higher degree of strain, resulting in a more worked and finegrained structure
of rolled material.
Recently a device for compression of samples in cross channel matrix CCE at braked
outflow of material has been designed and constructed. In this method, it is possible to obtain
a large strain value by multiple repetition of the process and flow restriction reduces the
tendency to cracking. Simulation tests have shown that for Fe-16Al-5Cr alloy it is possible to
obtain strain at   1/ pass, which the sixth cycle will provide   20. In addition, the cyclic
change in the way strain, causes a strong fragmentation initial structure of the material and
will have a positive effect on its mechanical properties.
In all these cases, the decisive role plays the shear and hydrostatic stresses.