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The paper presents an analysis of the impact of plastic deformation using hydrostatic extrusion (HE) on the structural, mechanical and functional properties of pure copper for use as electrodes in the process of electro discharge machining (EDM). As part of the research, copper was subjected to the HE process with the maximum cumulative true strain equal to ɛ cum  = 3.89 obtained in 5 stages. The result was, a refinement of the microstructure with the grains elongated in the direction of extrusion, with a cross-sectional size of d 2  = 228 nm. As the obtained material can be potentially used in the process of electro discharge machining, the copper specimens after the HE process were subjected to a comprehensive analysis to determine the mechanical, physical and functional properties of the material. A significant increase in strength (UTS) and yield strength (YS) of the HE-processed copper was obtained, reaching respectively UTS = 464 MPa and YS = 456 MPa at the maximum strain of ɛ = 3.89. Despite the clear strain-induced strengthening of the material, a very high electrical conductivity of not less than 97% was obtained. The electrodes made of copper after HE process have reduced erosion wear while maintaining a comparable or better quality of the machined surface. The best results were obtained for finish machining, where the electrical discharge wear was lower by 60% compared to the electrode made of non-processed copper. In addition, an improvement in the surface quality after the EDM process by 25% was observed when using the HE-processed electrodes., (© 2023. Springer Nature Limited.)

The study aimed to examine the effect of the hydrostatic extrusion (HE) process on the machinability of Ti grade 2 (Ti) in the turning process. After the deformation with true strain ɛ = 2.28, the microstructure was significantly refined to a grain size of 100 nm, resulting in an increase in the mechanical properties, UTS strength by 190%, YS yield strength by 230%Cutting forces for Ti in the initial state and after HE were analyzed at cutting depths a p  = 0.3 mm and 0.5 mm, the variables were cutting speed V c (20, 30 and 50 m/min) and feed rate f (0.08 and 0.13 m/s).The impact of the microstructure refinement in Ti after HE on the high cutting depth machinability deterioration (a p  = 0.7 mm) was identified. This phenomenon is particularly noticeable at lower cutting speeds V c  = 20 and 30 m/min at which cutting forces are higher. Application tests of Ti after HE showed a significantly lower susceptibility to buckling during threading. As a result of the tests carried out for the Ti in the initial state, it was not possible to achieve the tolerance of pitch diameter of the thread required by standards, d 2 at two of the three cutting depths tested. In turn, for the Ti after HE, the thread tolerances required by the standards were achieved for all tested cutting depths., (© 2022. The Author(s).)