In this thesis, tests of mechanical properties and chemical analysis and optical analysis of nanocomposites, aluminum alloy AlSi9Cu3(Fe) as a matrix and multi-walled carbon nanotubes as reinforcements were carried out. The nanocomposite was produced by high-pressure casting technology with a high cooling rate. Samples B and M1, which were prepared in 2019, were selected. Aluminum alloy AlSi9Cu3(Fe) has the property of precipitation hardening with aging, which is why tests were conducted to determine the change of successful nanocomposites that have this alloy as a matrix over a period of 3 years. For the chemical analysis, an optical emission spectrometer with the smoldering discharge excitation method of the LECO company type 500A was used. The chemical composition was tested with an optical emission spectrometer. Using an Olympus BX51 optical microscope and various magnifications, an analysis of the characteristic microstructures of AlSi9Cu3(Fe) alloy nanocomposite samples and carbon nanotubes was obtained. Energy dispersive electron microscopy was used to examine the distribution and stability of the reinforcement in the matrix and the influence of the reinforcement on the microstructure of the aluminum alloy. Electron microscopy was performed using an electron microscope manufactured by FEI type Quanta 250 FEG. Energy dispersive spectroscopy was carried out using an electron microscope and an OXFORT PentaFET X-ray detector, and microanalyses of individual phases in various colors were obtained for the purpose of comprehensive mapping of samples B and M1. Testing of the tensile strength properties was carried out using a Messphysik BETA250 universal tester at room temperature and according to the ISO 6892 - 1 standard. The results indicate an improvement of 20.7% in sample B and 9.7% in sample M1. The hardness according to Vickers was carried out on a Struers Duramin 2 device on metallographically prepared samples according to the norm for testing the hardness of metallic materials HRN EN ISO 6507 - 1. The results of the hardness measurement indicate an increase in hardness of 12.6% for sample B and 9.12% for sample M1.