Severe Plastic Deformation of Fe-22Al-5Cr Alloy by Cross-Channel Extrusion with Back Pressure

A new concept of the cross-channel extrusion (CCE) process under back pressure (BP) was proposed and tested experimentally. The obtained by finite element method (FEM) results showed that a triaxial compression occurred in the central zone, whereas the material was deformed by shearing in the outer zone. This led to the presence of a relatively uniformly deformed outer zone at 1 per pass and a strong deformation of the paraxial zone (3–5/pass). An increase in the BP did not substantially affect the accumulated strain but made it more uniform. The FEM results were verified using the physical modeling technique (PMT) by the extrusion of clay billet. The formation of the plane of the strongly flattened, and elongated grains were observed in the extrusion directions. With the increase in the number of passes, the shape of the resulting patterns expanded, indicating an increase in the deformation homogeneity. Finally, these investigations were verified experimentally for Fe-22Al-5Cr (at. %) alloy using of the purposely designed tooling. The effect of the CCE process is the fragmentation of the original material structure by dividing the primary grains. The complexity of the stress state leads to the rapid growth of microshear bands (MSB), grain defragmentation and the nucleation of new dynamically recrystallized grains about 200–400 nm size.

Effect of Deformation Homogeneity on Grain Refinement of AZ31 Magnesium Alloys Based on FEA during ECAP

In this study, the deformation process of AZ31 magnesium alloy during equal channel angular pressing (ECAP) was simulated using the commercial software Deform-3D under different extrusion condition (passes and temperatures). To investigate the effect of temperature and deformation rate on grain refinement, the rules of flow and deformation homogeneity and also the extrusion load during ECAP was discussed. The simulation results indicate that the AZ31 magnesium alloy obtain homogenous and larger strain magnitude after 4 passes ECAP at 250°C~275°C. To verify the 3D finite element simulation results, the microstructure in the cross-section was observed. It shows that the grain of AZ31 magnesium alloy is homogenous refined by finite element method (FEM) results, thus the mechanical property is improved.