Actual Problems in Machine Building 2020 Vol. 7 No. 1-2

Actual Problems in Machine Building. Vol. 7. N 1-2. 2020 Materials Science in Machine Building ____________________________________________________________________ 112 STRUCTURE AND THERMAL EXPANSION OF HIGH-ALLOY ALLOYS OF THE Al-Si-Cu SYSTEM FOR SPECIAL PURPOSES Popova M.V. , D.Sc. (Engineering), Associate Professor, e-mail: m.popova@rdtc.ru Malyuh M.A., Senior methodologist, e-mail: starostina_ma1976@mail.ru Siberian state industrial university, 42 Kirov str., Novokuznetsk, 654007, Russian Federation Abstract The influence of copper on the microstructure and temperature coefficient of linear expansion (TCLЕ) of Аl-30÷40% Si-Cu alloys was studied. The results of dilatometric studies have shown that the introduction of alloying elements in equal quantities leads to a decrease in the thermal expansion of the Аl-30%Si-30%Cu alloy to values of 6,0÷7,0·10 -6 deg -1 . Increasing the copper content to 40% not only does not lead to a further decrease in the TCLЕ values, but its increase is observed in the high-temperature test range. It was found that an alloy with an equal content of alloying elements Al-40%Si-40%Cu has the lowest TCLЕ values in the entire test interval (α 50-150 = 4,5·10 -6 deg -1 ) than triple alloys with the same total content of alloying elements, but with a different ratio. Metallographic analysis has shown that the introduction of copper into alloys with a non- eutectic composition of Al-30%Si-Cu, in which microstructure, in addition to eutectic, initially contains particles of the siliceous phase, contributes to an increase in the size of these particles. The structure of Аl-40%Si-Cu alloys is characterized by large plate crystals of the siliceous phase. Moreover, with an increase in the copper content to 50%, the volume fraction of eutectic decreases. It is shown that the limit of solubility of silicon in aluminum decreases with high copper content. Keywords aluminum, silicon, copper, alloying, structure, temperature coefficient of linear expansion.