Background and development of a high-silicon aluminum piston alloy. Part 1. piston alloys in the automotive industry of well-known world companies

Abstract

Increasing the efficiency and reliability of heavily loaded forced diesel engines operated in extreme thermally stressed conditions requires materials that ensure long-term stable operation of the piston pair at temperatures of 200–400 °C. In world practice, this is achieved by using hypereutectic aluminum alloys with a silicon content of 22–26%, the main advantage of which is a significantly lower coefficient of thermal expansion at high temperatures compared to hypoeutectic and eutectic piston alloys. According to the domestic standard for foundry aluminum alloys (DSTU 2839-94), only one alloy has a maximum silicon concentration of 22%.

The increase in the power of engines produced at Ukrainian enterprises, the approximation of their technical characteristics to European and world indicators necessitates the search for new solutions for the creation of an economically alloyed alloy of increased wear resistance, with the lowest possible thermal expansion, which is usually achieved by increasing the concentration of silicon. In the work, the solution to this problem was carried out on the basis of more than a century of experience of leading manufacturers of piston alloys. For this purpose, a systematization of alloys with a silicon content of 11 to 26%, used in the automotive industry of well-known world companies, was carried out. The features of their chemical composition and mechanical characteristics were analyzed in accordance with the range of operating temperatures. Among the 35 alloys considered, only four are high-silicon (> 22%), and the compositions of three of them coincide, which reduces the amount of information useful for substantiating the composition of the new alloy. Since three dozen piston alloys with a lower silicon content have proven their effectiveness at lower operating temperatures, when creating a new alloy, not only the ratio of silicon and alloying components, but also these components among themselves were studied. The traditional approach of searching for relationships between composition and properties did not yield results due to significant differences in the content of alloying components in alloys with the same silicon concentration. This necessitated the development of a new analysis method that takes into account the differences in the chemical composition of all known piston alloys. The peculiarity of the method and the effectiveness of its application will be considered in the second part of this article, and the structural-phase analysis of the alloy created using the original method will be considered in the third, final, part.