## 4 Conclusions  
Nanocomposite Al-\(\alpha\)-nano-Al\({}_{2}\)O\({}_{3}\) materials were synthesized via the chemical interaction between a salt melt containing rutile TiO\({}_{2}\) nanopowder and molten aluminum under the layer of molten halides in air atmosphere at the temperatures of 700-800 \({}^{\circ}\)C. Aluminum oxide nanoparticles were wholly wetted by aluminum and uniformly distributed over the \"in situ\" metal volume. The concentration of 100 nm Al\({}_{2}\)O\({}_{3}\) particles formed inside the aluminum matrix depended entirely on the exposure time and concentration of titanium dioxide in the melt. The mass fraction of aluminum oxide in the composite may have been increased up to 19 wt.%.  
Melting temperatures of composites with 4-19 wt.% of nano-\(\alpha\)- Al\({}_{2}\)O\({}_{3}\) did not differ from the aluminum melting point because of the uniform distribution of nanometer alumina inclusions in the composites.  
It was revealed that the tensile strength, yield strength, hardness, and ductility of cast Al-\(\alpha\)-nano-Al\({}_{2}\)O\({}_{3}\) composites in uniaxial tension increased up to 20-30% in the presence of \(\alpha\)-Al\({}_{2}\)O\({}_{3}\) nanoparticles in the structure of aluminum. The tensile strength reached maximum for the composites with 14 wt.% of \(\alpha\)-nano-Al\({}_{2}\)O\({}_{3}\), and it was the same for those with 19 wt.% of \(\alpha\)-nano-Al\({}_{2}\)O\({}_{3}\). This remarkable improvement of tensile strength was accompanied by a significant simultaneous increase in the elongation of nanocomposite by three times as opposed to the initial aluminum. The reason for such a combination of mechanical properties was the formation of very small nanoparticles of \(\alpha\)-Al\({}_{2}\)O\({}_{3}\) that were fully wetted and uniformly distributed in the aluminum matrix.  
Composite materials of the Al-Al\({}_{2}\)O\({}_{3}\) system could be easily rolled into thin and ductile foils and wires.  
Thus, the formed metal composite materials of the Al-Al\({}_{2}\)O\({}_{3}\) system combined the advantages of a low-melting metal matrix and the properties of a ceramic dispersive filler \(\alpha\)-Al\({}_{2}\)O\({}_{3}\), which makes this system an extremely attractive structural material, that is very light, strong, hard, and elastic.  
A possible mechanism for the simultaneous increase in mechanical properties and elongation in tension when true aluminum oxide nanoparticles are introduced into the Al-Al\({}_{2}\)O\({}_{3}\) composite will be the subject of our further study.  
Data curation, L.A.Y.; Formal analysis, L.A.Y.; Investigation, A.G.K., D.I.V. and E.O.S.; Methodology, L.A.Y.; Writing--original draft, L.A.Y. All authors have read and agreed to the published version of the manuscript.  
The work was funding by the Research Program No 122020100210-9 (IHTE UB RAS), Russian Academy of Sciences, Ural Branch, Russia.  
Not applicable.  
This work was carried out using equipment at the Shared Access Center for the Composition of Compounds, Institute of High-Temperature Electrochemistry, Ural Branch, RAS (Ekaterinburg, Russia) for analytical support and the Shared Access Centre \"Plastometry\", Institute of Engineering Science, Ural Branch, RAS (Ekaterinburg, Russia) for mechanical testing.  
The authors declare that they have no known competing financial interest or personal relationships that could have appeared to influence the work reported in this paper.