## 2 Experimental Details
### Working Procedure  
The main difficulty encountered in the production of composites with metal matrix based on aluminum and SiC reinforcement is the low wettability of ceramic materials by the metal bath [41; 42]. There are a number of studies that have shown that the coating of SiC particles with a metal such as Si, Fe, Mn, or Cu results in a substantial increase of their wettability. [PERSON] and [PERSON] clearly demonstrate that the addition of metallic Cu to the surface of SiC particles considerably increases their wettability by molten aluminum [42]. In the present research, the authors started from the considerations presented above and did not aim to measure the wettability of SiC particles in aluminum alloy but to demonstrate the applicability and advantages of the method. The SiC particles were coated with Cu in order to improve their wettability in the molten alloy metal bath. The coating of the SiC particles with a thin layer of copper was  
Figure 1: Centrifugal casting installation, with vertical rotation axis. **(a)** Experimental device, **(b)** casting process, **(c)** casting shell design. performed by a two steps process: Step 1, the activation of the particle surface and step two consisting in the actual coating process. To improve the adhesion of Cu to SiC particle's surface they were activated in a solution with the following composition: 500 mL H\({}_{2}\)O, 0.5 mL HCI, and 0.25 g of PdCl\({}_{2}\). The activation process followed these steps:  
* 100 g of SiC particles were introduced in the activating solution then mixed with the magnetic stirrer for 30 min;
* SiC particles were filtered and washed;
* SiC particles were acclinated at 150 \({}^{\circ}\)C for 40 min (heated together with the furnace). After the activation, the particles were submerged for 60 min (with sample collection after 30 min) in a coating solution having the following composition: 2000 mL distilled H\({}_{2}\)O, 20 g CuSO\({}_{4}\), 20 g NaOH, 100 g KNaC\({}_{4}\)H\({}_{4}\)O\({}_{6}\)\(\cdot\)4H\({}_{2}\)O, 20 mL CH\({}_{2}\)O. An empirical calculus was used to determinate the copper requirement within the coating solution, based on the following simplifying hypotheses:  
* All SiC particles were considered perfectly spherical;
* A medium granulation value of 137\(\upmu\)m was considered. It should be mentioned that SiC powder was supplementary sorted by particles size criteria in order to increase its uniformity;
* An even layer of Cu of 1\(\upmu\)m was considered on the surface of SiC particles. Based on these simplifying hypotheses and taking into account that 25 g SiC charges were used, the result was a need of 8 g of CuSO\({}_{4}\). In order to have the safety of a sufficient content of Cu in the coating bath, the presented composition was reached (containing 2.5 times more CuSO\({}_{4}\) than the calculated minimum necessary). The working parameters for both activation and coating stages are presented in Table 2.  
For the embedment of the SiC particles into the aluminum alloy metallic base, three different variants of the centrifugal casting process with vertical rotation axis were used:  
V\({}_{1}\)--The alloy overheated at 850 \({}^{\circ}\)C was poured in the resting (nonrotating) shell. Afterwards, the Cu-coated SiC particles were introduced and preheated to 900 \({}^{\circ}\)C. Then the shell was rotated with 1500 rpm speed. It should be mentioned that after the solidification of the composite sample it was found that during the pre-heating stage the agglomeration of SiC particles occurred. V\({}_{2}\)--followed the same steps as the first version but this time the agglomerations of particles were crushed and only afterwards introduced in the shell. V\({}_{3}\)--room temperature uncoated SiC particles were introduced into the resting shell, which was afterwards rotated with 1500 rpm until solidification of the alloy. The casting of the aluminum alloy was done while the shell was rotating.