Aluminium alloy (AA6082) is a medium-strength, lightweight alloy with excellent corrosion resistance in aerospace structural parts and marine applications . Considering modern engineering disciplines, metal matrix composites incorporate two or more reinforcements that can meet the needs of a viable alternative to traditional materials . The most frequent machining procedure for hard materials is electrical discharge machining (EDM). A spark is created between the electrode and the workpiece to remove the material. Any hard material may be machined until it becomes electrically conductive. Ceramic composites containing boron nitride (BN) and molybdenum disulphide (Mos2) are employed in various high-temperature applications. Due to its intrinsic properties like hardness, high stiffness, low density, electrical conductivity, and very high strength, used in aircraft engines, level sensors, wear-resistant components, industrial wear, plastic forming, and complex moulds for metal and heat exchangers applications . An electro-thermal approach is electrical discharge machining (EDM). In a dielectric medium, a direct current pulse generator generates high-frequency electric sparks between an electrode and a workpiece. The melted and evaporated workpiece surface develops a final shape that adheres to the electrode geometry. Kumar et al.  conducted the machinability analysis on AISI 420 stainless steel alloy using die-sinking EDM. Taguchi based grey relational analysis (T-GRA) used multi-variable optimisation to find the best optimal process parameters. The process parameters considered were gap voltage (V), pulse on time (Ton), and Pulse current (A); output characteristics were material removal rate (MRR) and electrode wear rate (EWR). The results show that pulse current was influenced by 63.71%, gap voltage by 13.26%, Ton by 10.88% and improvement in grey relational grade by 0.086.
In another study, Mukherjee et al.  investigated the machining studies on titanium foam by EDM under chamfered and hollow electrodes. In comparison to other process factors, the results show that current is the most important factor in electrode wear rate. Chamfered electrodes produce a hole with an oversize of 0.43%, with maximum MRR achieved using a hollow electrode. Tao Le  examined the powder mixed EDM (PMEDM) processes of SKD61 steel. By modifying process parameters such as Ton, peak current, and powder concentration, tungsten carbide powder mixed concentration was employed as a dielectric medium to achieve MRR and tool wear rate. Peak current, Ton, and powder concentration have been shown to effect surface integrity, with the MRR increasing by 63.36%.
Machinability performances were investigated on titanium alloy by using WEDM. The optimisation of process parameters was optimised by using a neural network. This proposed methodology helps to minimise machining time by increasing production and process efficiency . Karthikeyan et al.  conducted the WEDM experiment on nickel-base superalloy (MONEL K-500). The process variables considered were Wire Tension (WT), Wire Feed Rate (WFR), Gap Voltage (GV), pulse off time (Toff), and Ton, varied by five levels. The Taguchi L25 orthogonal array is used to assess output characteristics such as Surface Roughness (Ra), Material Removal Rate (MRR), and Kerf Width (k), and machining reaction variables are optimised using the T-GRA technique. Zhang et al.  performed the ultra-sonic assisted and powdered mixed EDM experiment on the 7Cr13Mo steel. The results show that 78% of microhardness was increased, and 57% of MRR was enhanced. In another study, By using a powder metallurgy electrode, Sarmah et al.  was able to successfully modify the surface of Al-7075 alloy. When compared to the substrate material, the deposited layer has 1.5–2.5 times the micro-hardness. The machinability of Inconel 718 alloy underwire cut EDM and die-sinking EDM is investigated by Li et al . The results demonstrate that copper coated SiC electrodes with greater MRR, EWR, and surface morphology were employed as electrodes (i.e. roughness and topography). In terms of EWR, surface roughness, and MRR, the manufactured Cu-Sic electrode performs better.
The machinability of EDM was investigated utilising an environmentally friendly form of EDM, namely (near dry and wet) circumstances. Pulsed off time and Ton were the process parameters that were examined. Two-phase dielectric mediums (air and EDM oil) are employed in near-dry circumstances, whereas EDM oil is used in wet settings. The approach of gas chromatography and mass spectrometry is used to analyse gas emissions. The results show that the parameters were optimised to achieve higher MRR with a reduction in gaseous emission of about 97%.. Singh Bains et al.  performed the magnetic field-assisted EDM on SiC reinforced aluminium composite materials. To accomplish the output performance characteristics of MRR and Surface roughness, the input process parameters of Toff, Ton, peak current and magnetic field intensity, sic percentage of distribution, and tool electrode material were analysed. Magnetic field-assisted EDM produced increased surface quality and MRR, according to the findings. In the drilling process, machining experiments on nickel-titanium shape memory alloys were explored. The process parameters were optimised to achieve micromoles with reduction in machining time of about 50–65% compared to the standard EDM process. Karthik Pandiyan et al.  investigate the machinability studies on Al/Sic composites using RSM. The process parameters selected in this study were peak current, Toff and Ton; on output characteristics evaluated were surface roughness and MRR. The desirability function analysis methodology was employed to predict the optimum level of parameters to achieve higher MRR with lowered surface roughness. Similar work was also carried out by Karthik Pandiyan et al.  using Al/ SiC composites by using EDM. The current, peak current and gap voltage parameters were considered to achieve MRR, TWR and Circularity and cylindricity utilising the MCDM Codas method.
Mechanical and tribological properties were evaluated on the AA6061-T6/ Sic composites. The results show that the addition of reinforcements enhanced composite materials' mechanical and tribological properties.. The tribological and Mechanical characteristics of Zro2/Al2014 composite materials were fabricated using stir casting methodology. The results show that the addition of reinforcements enhances the properties of composite materials..Abrasive wear studies were carried out on polypropylene/cloisite 30B/ elvaloy AC3427 nanocomposite fabricated using the melt intercalation method. Tribological studies were employed by using a two-body abrasive wear methodology..Optimisation of process parameters was carried out during the EDM machining for biomedical devices for their biocompatibility to enhance the high standard necessities for biomedical materials and their applications in implant manufacturing..Machining studies were carried out by tungsten carbide (WC) coated electrode material on Ti-6Al-V alloy. The process parameters considered were frequency and width, voltage and current to achieve output characteristics on MRR and TWR and overcuts were examined. The process parameters were optimised by using GRA and ANOVA methodology .
Machinability studies on AISI-D3 steel were examined by using EDM. The process parameters influence the machinability nature of the materials by tool rotation on surface integrity, TWR and MRR. The results show that tool rotation influences about 49% enhancement in MRR and surface roughness enhancement of about 10%..Optimisation studies were carried out on EDM machining of Monel 400 alloy by copper titanium diboride electrode material. The tiB2%, Ton, current, and flushing pressure achieve output characteristics like MRR and TWR . Traditional electrode and cryogenic cooled electrode materials employed machinability examination on Al/10% SiC composites. The results show that cryogenic cooled electrode material reduces the electrode wear rate by 18%..Machinability examinations on AISI-D2 steel by the CCEDM process reduced wear rate by about 20% and surface roughness by about 18% . Machinability and optimisation studies were carried out on OHNS steel to achieve higher MRR with lowered surface roughness and machining time employing optimum process parameters. The best process parameters were determined using GRA and ANOVA methods . Stanojkovic and Radovanovic  successfully used the COPRAS technique in a high-pressure coolant drilling procedure on Al alloy with a carbide tool. Varatharajulu et al.  performed a drilling experiment on magnesium AZ1 alloy and optimised the desirability function technique using TOPSIS and COPRAS top rankings. With a spindle speed of 4540 rpm and a feed rate of 0.076 mm/rev, the best combination was discovered using TOPSIS and COPRAS for simultaneous minimisation of all answers. For supplier selection, Ghorabaee et al.  examined the COPRAS approach in interval type-2 fuzzy sets. Mishra et al.  investigated the COPRAS technique for assessing the bioenergy production process's long-term viability. To analyse city compactness, Jurgis et al.  used the COPRAS technique. To choose effective dwelling house walls, Zavadskas and Kaklauskas  examined the COPRAS approach.
The literature reveals no such works related to fabrication and Machinability studies using electrical discharge machining of AA6082/ 3 wt. % BN/1% MoS2 hybrid composites. Most authors used traditional optimisation methodologies like GRA, Taguchi, and RSM techniques to investigate the parameters. Multi-criteria decision making methodology was not yet used to optimise the process parameters. MCDM approach based complex proportional assessment (COPRAS) approach was not used to optimise process parameters while machining the AA6082/ 3 wt. % BN/1% MoS2 hybrid composites. Parametric optimisation examinations were engaged in assessing the effect of process parameters like IP, Ton, and gap voltage on MRR, EWR, CIRC, and CYLD during the machining of composite materials. The current study investigates the multi-objective optimisation of process parameters by MCDM based COPRAS method. The best optimum process parameters were achieved from the COPRAS quantitative assessment scores. The results revealed higher MRR with lowered EWR, CIRC and CYLD as output performances were enhanced.
A flow chart for the current study involves the fabrication, machining and optimisation of entropy weights integrated with COPRAS methodology are represented in Fig. 1.
Figure 1 : Schematic layout of fabrication, machining, and optimisation of hybrid composites