Kovalyova V. Formation of quasicrystal structure in surface layers of aluminium alloys during laser alloying

The object of this thesis is structural-phase state and mechanical properties of the surface layers aluminum alloys after laser alloying powder of mixture with Cu-Co and Ni-Co.The purpose it was establishing mechanisms formation structures in the aluminium and silumin's surface layers during laser alloying with mixture of powder of transitional metalls Cu-Co and Ni-Co. Methods of researches: x-ray, metallographic, electron microscopy analisis and method of measuring microhardness. It has been shown that under pulsed laser alloying of aluminum by Cu-Co and Ni-Co powder mixture the peculiar heterophase dispersed structure in the surface layers can be formed; one component of this strucrure is a quasicrystal decagonal phase. It was found that the presence of high-resistant dispersed intermetallic phases, in particular decagonal quasicrystal phase in the alloying zone, leads to a significant increase of the average microhardness of matrix material. A new method of modeling the reciprocal lattice decagonal quasicrystal structure based on the Fibonacci sequence interpretation has been proposed and used. The application of this method appreciably simplifies process of diffraction maximums indexing of the decagonal phase and allows applying for them three-indexing notation. The results can be used to create a wear-resistant coatings in places of local products based on aluminum and its alloys, the use of which can improve the tribological properties of friction pairs parts of working mechanisms. The results obtained by modeling the reciprocal lattice can be applied to traditional indexation of diffraction maximums from decagonal phases by three indices. Methods and experimental research data introduced to educational process in the lecture course "Non-crystalline materials" and used when to working on magister and graduation work at the Physics of Мetals Department of Zaporizhzhian National University.