## 2 Materials and Methods  
Composites based on Al-2.5%Fe alloy reinforced with 0.12% graphene were investigated. The synthesis of such aluminum-matrix composites was described in detail in [29; 30; 31; 32] and involved the reaction of a molten Al-2.5% Fe alloy used as the matrix with a carbon-containing precursor under a layer of molten halide salts (sodium and potassium chlorides with the addition of ammonium fluorides). Molten salts were used as salt flux. Boron carbide was used as the carbon-containing precursor in the synthesis of composites based on Al-Fe alloy. The amount of boron carbide was 2 mass %. The synthesis temperature was 750 \({}^{\circ}\)C, and the time the liquid Al-Fe alloy was held in the molten salt was 1-5 h. The synthesis of the carbon atoms was a one-step process taking place directly in the molten alloy. Initially, in the process of self-assembly, carbon clusters were formed, followed by the appearance of continuous films that were evenly distributed in the volume of the solidifying melt. Cylindrical samples 10 mm in diameter and 70 mm in height were cast into a metal mold. The structures and properties of the composites were compared with the corresponding characteristics of the Al-2.5%Fe matrix alloy cast under the same thermophysical conditions. The content of carbon and iron in the composites was evaluated via spectral analysis using ICPE-9000 SHIMADZU spectrometer with inductively coupled plasma (the error was \(\pm\)0.005 wt.%) (Table 1). Carbon in the Al-Fe matrix was examined using Raman spectroscopy via a Renishaw U-1000 instrument. The spectral lines were approximated using the built-in Wire-30 software package and Fityk 0.9.8 data analysis application. Thermal conductivity was measured on a NETZSCH LFA 467 Hyper Flash device using the laser flash method according to ASTM E-1461, DIM EN 821, and DIN 30,905 international standards. Severe plastic deformation (SPD) of the composite and the matrix alloy was induced for samples with a 1 mm thickness and a 10 mm diameter via high-pressure torsion (HPT) at a pressure of 4 GPa at room temperature. There were n = 5 and 10 anvil revolutions, and the true strain values at the mid-radius of the samples were \(e\) = 3.54 and 4.13, respectively. The macrostructure of the samples was studied by means of a NEOPHOT-32 optical microscope and a scanning electron microscope (SEM) (TESCAN MIRA 2, equipped with an Oxford Instruments UltimXmax energy-dispersive X-ray spectral microanalysis (MRSA) system with AZtec 5.1 software). The samples for structural analysis were prepared with the application of mechanical polishing in a Cr\({}_{2}\)O\({}_{3}\) suspension. Final polishing was performed on a suspension of colloidal silicon dioxide. Fine-structure examination was performed using TECNAI G 30 Twin transmission electron microscope (TEM) with an accelerating voltage of 300 kV. The samples for fine-structure examination were made via jet polishing in a Tenuppol-5 device in a solution of 20% nitric acid and 80% methanol at a temperature of \(-\)25 \({}^{\circ}\)C and a voltage of 15-20 V.  
X-ray diffraction analysis was performed using a Bruker Advance-D8 diffractometer with CuK\({}_{\alpha}\)-radiation (K\({}_{\alpha}\) = 0.15418 nm) at scattering angles of 18-145\({}^{\circ}\) with a step of 0.02\({}^{\circ}\) and 2 s exposure time. The diffraction patterns were analyzed using DIFFRAC.EVA 4.0, DIFFRAC.TOPAS 5.0 software, and PDF 2.1202 database. Billets in the form of thin rods with dimensions of 10 \(\times\) 1 \(\times\) 1 mm for the cast samples and 10 \(\times\) 1 \(\times\) 0.3 mm for the deformed samples were cut via the electric spark method for use in the specific electrical resistance measurements.