Ekstremalna Deformacja – przystępny, dwujęzyczny artykuł o ekstremalnych odkształceniach plastycznych w metalach

Severe plastic deformation leads to the refinement of the microstructure of materials, resulting in improved mechanical properties. To prevent loss of material cohesion during deformation, high compressive stresses must be maintained in the deformation zone.

The paper presents the beneficial effect of high pressure on increasing ductility and preventing cracking through the use of equal channel angular pressing (ECAP) and hydrostatic extrusion (HE). The design of the presses, their main performance characteristics, and process parameters are described. A hydrostatic extrusion press with a diameter of 22 mm operating up to 2 GPa and an ECAP setup with a 30 mm cross-section and pressure up to 2.3 GPa are characterised, including structural optimisation using analytical methods based on Lamé’s theory of elasticity and plasticity, as well as the finite element method (FEM). The materials of the working chambers and key process parameters are analysed.

The reduced nodal stresses in the ECAP chamber made of S600 steel and the HE chamber made of 45HNMFA steel showed that strength limits are not exceeded under maximum loads. For aluminium alloy 6060, the optimal corner angle of the square ECAP channel is 16°. FEM analysis demonstrated the non-uniformity of plastic deformation during hydrostatic extrusion of a square copper profile, as well as areas of strain localisation during extrusion of a complex titanium profile.

The study also describes the ease of combining both SPD techniques and their application to enhance grain refinement down to the nanometre scale. It was shown that microstructure refinement using high-pressure deformation methods leads to an increase in strength of over 70% (for copper and Ti grade 5 alloy) and an increase in yield strength of over 100% (for nickel alloy C65500 and aluminium 5483). Potential applications of the processed materials include medical instruments and implants, fasteners, welding tooling, and complex pipes and profiles.