Loza K. Influence of modification and heat treatment on the formation of structure and properties of the secondary piston alloy АЛ25.

Object of research – the processes of structure formation during crystallization, heat treatment and exploitation of the pistons, the causes of their destruction, the influence of structure on the complex of mechanical and service properties of the alloy АЛ25. Subject of research – the structure, physical and mechanical properties of the piston alloy АЛ25, obtained by different technological options. Purpose of research – the formation of specified structure and physical and mechanical properties of the secondary piston alloy during the crystallization process under the influence of the modification, heat treatment and exploitation. Research methods – control of chemical composition by the means of spectral analysis on the spark spectrometer "Spectro-Max"; optical and electron microscopy; phase qualitative and quantitative X-ray spectral microanalysis; static specimen tests with the purpose of strength, plasticity, hardness characteristics determination; research for determination of long-term strength at 300°C; determination of the temperature coefficient of linear expansion with the use of the dilatometric method; bench and industrial tests of finished products. Obtained results – with the purpose of structure stabilization and increasing of alloy АЛ25 quality the modification technology has been developed. It provided obtaining of the necessary structure (equiaxed sections of alpha-aluminum solid solution, surrounded by lamellar inclusions of beta-silicon solid solution and compact inclusions of intermetallic compounds), decreasing of the temperature coefficient of linear expansion and gas saturation of the alloy. Implemented at JS "Motor Sich". Area of application – low-power internal combustion piston engines for consumer goods and unmanned aircrafts, machine-building indusrty.