## 2 Materials and Methods
### Material Characterization  
Light microscopy (LM) and SEM were used to analyze the S1, S1-HT, S2, and S2-HT microstructures. Before LM and SEM, the specimens were polished using SiC-based abrasive papers with 500-2000 grit and polycrystalline diamond slurry with 9 and 3 \(\upmu\)m grain sizes to achieve high light reflection and eliminate microroughness. A specialized surface-active suspension, Eposil F (QATM, Mammelzen, Germany), with a 0.1 \(\upmu\)m fraction diluted with a special etchant for aluminum, was used for surface etching to reveal the microstructural features and improve the image contrast. LM images were acquired using an Axioscope 5 microscope (Carl Zeiss, Oberkochen, Germany), and SEM images were acquired using a Crossbeam 540 microscope (Carl Zeiss, Oberkochen, Germany) at an accelerating voltage of 10 kV. Figure 3: Schematic representation of mechanical cutting for obtaining specimens to analyze the characteristics of the obtained materials. A high-resolution X-ray diffractometer, Rigaku SmartLab (Rigaku Corporation, Tokyo, Japan), equipped with a monochromatic copper (Cu) X-ray source with wavelength K\(\alpha\) = 1.540 A was used to perform X-ray diffraction (XRD) of the specimens. XRD patterns were obtained in the range of scanning angles 20 from 5\({}^{\circ}\) to 75\({}^{\circ}\), which provided a wide range of diffraction peaks for analyzing the phase composition of the specimens. The scanning time for each specimen was approximately 10 min, which provided sufficient accuracy to identify characteristic phase components and their intensities. The densities of cut disk-shaped specimens S1, S1-HT, S2, and S2-HT were determined according to the technique described in [39]. The hydrostatic method was used to determine the density, which included measuring the mass of the specimens in air (m\({}_{\mathrm{a}}\)) and after their complete immersion in distilled water (m\({}_{\mathrm{w}}\)), taking into account the density of water at 23 \({}^{\circ}\)C: \(\rho_{\mathrm{w}}\) = 0.9975412 g/cm\({}^{3}\)[40]. Mass measurements were performed using an electronic densitometer MH-300A (Shenzhen Omena Technology Co., Ltd., Shenzhen, China), which provided highly accurate results. The theoretical density of the specimens (\(\rho_{\mathrm{th}}\)) was calculated based on the mixture rule. The density values of aluminum (\(\rho_{\mathrm{Al}}\approx 2.68\) g/cm\({}^{3}\)), microsilica powder (\(\rho_{\mathrm{ms}}\approx 2.45\) g/cm\({}^{3}\)), and their mass fractions in the material (wt\(\%\)) were used in the calculations. The final theoretical density was calculated using Equation (1):  
\[\rho_{\mathrm{th}}=\rho_{\mathrm{Al}}\times\mathrm{wt}\%_{\mathrm{Al}}+\rho_ {\mathrm{ms}}\times\mathrm{wt}\%_{\mathrm{ms}} \tag{1}\]  
The experimental density (\(\rho_{\mathrm{exp}}\)) of the specimens was determined by measuring their masses using a densitometer and was calculated according to Equation (2):  
\[\rho_{\mathrm{exp}}=(\mathrm{m_{a}}/(\mathrm{m_{a}}-\mathrm{m_{w}}))\times \rho_{\mathrm{w}} \tag{2}\]  
The porosity was determined using Equation (3), which accounts for the difference between the theoretical density of the material and its experimental (actual) density:  
\[\mathrm{Porosity}=(\rho_{\mathrm{th}}-\rho_{\mathrm{exp}})/\rho_{\mathrm{th}} \tag{3}\]  
The obtained density values made it possible to estimate the pore fraction in the specimens, which is an essential parameter for understanding their mechanical properties. The microindentation method according to ASTM E 384 [41] was used to evaluate the hardness of the specimens. The tests were conducted at room temperature using a Vickers HVT-1000A microhardness tester (Laizhou Laihua Testing Instrument Factory, Laizhou, China). A load of F = 100 gf (0.1 kgf) was applied to the surface of the specimens for 15 s at five different points on each specimen to ensure high accuracy and reproducibility. The values of the diagonals of indentations made in the shape of a pyramid with an apex angle of 136\({}^{\circ}\) were used to calculate microhardness.