## 2 Materials and Methodology  
In this study, commercially available silicon-brass Copper alloy, also termed C87600 alloy was considered as the matrix phase for the composites, where zinc and silicon are the primary alloying element with traces of iron and magnesium. The elemental composition of the C87600 alloy (as received) is presented in Table 1. This alloy exhibits high wear and corrosion resistance behavior along with excellent conductivity. The copper alloy C87600 does not respond to heat treatment. It is usually used in marine shafting, architectural appliances, etc., due to its exceptional wear resistance, corrosion resistance, and electrical conductivity. Table 2 presents the physical properties of the C87600 alloy. To fabricate the hybrid composites, SiC, WC, and Gr micro-particulates with 99% purity were bought from Vision Casting Pvt. Ltd., Hyderabad. Besides the base matrix alloy, two sets of copper hybrid composites were fabricated considering SiC-Gr and WC-Gr composites. The graphite particle being considered as secondary reinforcement, its content in the hybrid composites was kept constant at 1 wt.%, whereas the weight percentages of SiC and WC varied at 3 wt.%, 6 wt.%, and 9 wt.%, respectively. These hard ceramic constituents were selected as the reinforcing phase as these materials tend to enhance the physical characteristics to a significant extent [17; 18]. The copper-based hybrid composite materials were fabricated through the stir casting process due to their cost-effectiveness and favorable for mass production [19]. Firstly, the copper alloy (C87600) ingots were kept in a high-temperature sustaining graphite crucible and heated in an electric furnace at a temperature of 1200 \({}^{\circ}\)C, which is above its melting limit. After the ingots reached a fully molten state, the pre-heated reinforcements (heated at a temperature of 600 \({}^{\circ}\)C for 1 h) were introduced to the copper melt for the manufacture of the composites. Pre-heating the reinforcement is necessary to remove any moisture content. In this stage, the reinforcements were either SiC or WC particles as per the compositions. The mechanical stirrer was attached to the furnace, which was uninterruptedly stirred at 400 rpm for 15 min to obtain the homogenous distribution of the reinforcement particles. Thereafter, the graphite particles of 1 wt.% content were introduced to the copper melt for the development of hybrid MMCs. The stirring action was continued for another 15 min with the same speed to effectively distribute the reinforcements in the molten copper alloy. The complete process was conducted with argon gas shielding to evade any contamination of the molten metals with atmospheric gases. Further, the degasser (C\({}_{2}\)Cl\({}_{6}\)) was added to the molten alloy to get rid of any dissolved hydrogen gas existing in it. After removing the slag from the surface, the molten metals were poured into a metallic split die, which was preheated at a temperature of 600 \({}^{\circ}\)C. Pre-heating the die was necessary to minimize the temperature gradient and shun the chilling effect while pouring the molten metals. Moreover, the pre-heating process also removes the moisture and oil present on the exposed faces, thus avoiding any surface porosity defects. Figure 1 represents the schematic representation of the stir casting setup used for the manufacturing of the copper-based hybrid MMCs. Different compositions of the fabricated copper MMC are presented in Table 3. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Element** & **Zn** & **Si** & **Mg** & **Fe** & **Cu** \\ \hline
**Weight\%** & 4.5 & 5.5 & 0.04 & 0.02 & Remaining \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Elemental composition of silicon-brass Copper (C87600) alloy.