Impact of process parameters of plastic deformation by the hydrostatic extrusion method on properties of metals and metal alloys for industrial applications

In the face of the clearly growing trend accompanying the scientific research, related to their practical use in industry, intensive research on hydrostatic extrusion (HE) technology was launched in the Laboratory of Plastic Deformation Under High Pressure, with a view to its commercial applicability. Hydrostatic extrusion, due to the feasibility of plastic working of relatively large volumes of material, leads to production even of several-meter long products in the form of round or shaped rods and shows a strong commercial potential. The work presents the practical use of the hydrostatic extrusion process for production of finished and semi-finished products from materials with highly refined grains. The results presented here concern 5XXX series aluminium alloys with a highly refined microstructure (average grain size ~ 100nm) and significantly increased strength (ultimate tensile strength ~ 500 MPa) for fastener applications. Other described materials, that are also dedicated to fasteners, are titanium and austenitic steel 316L. Both materials are characterized by a clear, more than twofold increase of mechanical properties after the HE process, reaching ultimate tensile strengths of 1100 - 1200 MPa, with a strong refinement of the microstructure down to the nano-scale. The last described material, CuCrZr copper alloy, combines both the features of improved mechanical properties, optimization of its electrical conductivity and hardness allowing its commercial use as electrodes for spot welding in the automotive industry. The tests results presented in this paper, carried out on finished electrodes made from the material after the HE process, indicate an increase in electrode lifetime by several times.