In this present research work, a new modelling of energy density in EDM (Electrical Discharge Machining) is proposed. Energy density can be defined as the amount of energy needed to get a unit volume of material removed, and for its modelling, the whole EDM process has been taken into account. This new definition lets us quantify the energy density that is being absorbed by the workpiece and the electrode. Results are compared to those obtained by die sinking EDM in an Inconel ^®600 alloy using Cu-C electrodes. Currently, this material is of great interest for industrial applications in the nuclear, aeronautical and chemical sectors, due to their combinations of good mechanical properties, corrosion resistance and extreme hardness at very high temperatures. The experimental results confirm that the use of negative polarity leads to a higher material removal rate, higher electrode wear and higher surface roughness. Moreover, the optimal condition to obtain a maximum MRR (Material Removal Rate) of 30.49 mm³/min was: 8 A, 100 µs and 0.6, respectively, for the current intensity, pulse time and duty cycle.

Today, there is a growing demand for efficient hole manufacturing technology in many industries such as aeronautics, automotive and nuclear, among others. Thus, the present study deals with the machining of through holes on SiSiC advanced ceramic by using Electrical Discharge Machining (EDM) drilling technology. Since recommendations related to the electrode characteristics and settings parameters are found to be scant for the industrial use of EDM drilling of SiSiC ceramics, this research work comes to cover this gap as it presents a complete study focused on the influence on different electrodes under rough and finish machining conditions. In particular, the influence of four electrodes materials (copper, copper-tungsten, graphite and copper infiltrated graphite) and three different electrode diameters ranging from 2 to 4 mm are investigated. In addition, the rotational speed of the electrode is also analysed. From the experimental results, both electrode material and machining regime, seem to be the most relevant factors of all. In the case of 2 mm diameter electrode, material removal rate (MRR) with Cu electrode was, approximately, 4.5 times higher than that obtained with a C electrode. In fact, it was found that copper electrode rotating at 20 rpm combined with high values of discharge energy (I = 2 A; t_i = 70 µs) is the most economical option in terms of production cost and production time, as it gives a high MRR of 0.4754 mm³/min and a minimum electrode wear (EW) value of 7.52%. Moreover, slightly higher values of MRR were achieved for CuC electrode compared to those obtained with C electrode, indicating that the addition of Cu in the electrode contributes to a greater removal of material. However, a value of Ra of 0.37 µm could be obtained by setting low current intensity values (I = 0.5 A; t_i = 45 µs) combined with C electrodes and with no rotation.

Pure commercial Cu of 99,98 wt % purity was processed at room temperature by Equal- Channel Angular Pressing (ECAP) following route Bc. Heavy deformation was introduced in the samples after a considerable number of ECAP passes, namely 1, 4, 8, 12 and 16. A significant grain refinement was observed by transmission electron microscopy (TEM). Tensile and microhardness tests were also carried out on the deformed material in order to correlate microstructure and mechanical properties. Microhardness measurements displayed a quite homogeneous strain distribution. The most significative microstructural and mechanical changes were introduced in the first ECAP pass although a gradual increment in strength and a slight further grain refinement was noticed in the consecutive ECAP passes.

The most important difficulties when the behaviour of a part that is subjected to external mechanical forces is simulated deal with the determination of both the material thermo-mechanical properties and its boundary conditions. The accuracy of the results obtained from the simulation is directly related to the knowledge of the flow stress curve. Therefore, the determination of a material flow rule which is valid for both a wide temperature range and different initial deformation conditions in the starting material presents a great deal of interest when simulation results close to the experimental values are required to be obtained. In this present study, a novel flow stress curve is proposed that is able to accurately predict the behaviour of both materials with no previous accumulated strain and materials that have been previously subjected to severe plastic deformation processes. Moreover, it is possible to use it both for hot and cold working. The results are analysed in a wide test temperature range, which varies from room temperature to 300 °C, and from material previously processed by angular channel extrusion or with no previous strain accumulated. It is shown that the flow rule proposed is effective to model the material behaviour in a wide temperature range and it makes it possible to take the recrystallization phenomena that appear in previously deformed materials into account. In addition, the results obtained are compared with those predicted by other flow rules that exist in the prior literature. Furthermore, the study is complemented with finite element simulations and with a comparison between simulation and experimental results.