MANDZIEJ Stan Advanced Materials Analysis

Severe plastic deformation with self-recovery or post-deformation recovery has been frequently applied in the last two decades to manufacturing of nano-structured materials, inspired by the Hall-Petch relation between the strength of alloys and their grain size. Relatively soon was realized that natural limits occur imposed by the processed materials and it was early defined that ultimate grain refinement of single-phase alloys makes little sense as it leads to fast deterioration of properties or failure of the material due to dynamic release of energy stored in it. Therefore efforts were directed towards development of new compositions of multi-phase alloys in which dynamic recovery and recrystallisation processes could be hampered by precipitation. To study these processes with their adequate control, a working device was developed called MaxStrain, combined with Gleeble physical simulator. The MaxStrain uses two-directional deformation to reach accumulated strains of 50 and more, depending only on the ductility of processed alloy, applying plane strain compressions with constant strain rates of up to 100/sec, combined with various programmable thermal cycles. In this paper examples are given of processing Al-6061 grade wrought alloy and Al-319 grade cast alloy, and resulting microstructures described. The precipitation processes accompanying the recovery and recrystalisation during the severe plastic deformation were studied by mainly metallography, including transmission electron microscopy.