Effect of Melt Treatment with Water Vapor on Thermal Expansion of Alloy Al – 20–40% Si

Abstract

The effect of melt treatment with water vapor on the microstructure and linear thermal expansion coefficient (LTEC) of Al–(20–40)% Si alloys is studied. LTEC values are determined in the temperature range of 50–450 °C. It is established that melt treatment with water vapor has not only a modifying effect on the structure of high-silicon silumins, but also affects the value and nature of the change in LTEC making it possible to reduce its values at test temperatures of 50–250 °C. The efficiency of melt treatment in a water vapor atmosphere depends on silicon content and decreases with the increase of its content in the alloy. A regime for alloy modification providing maintenance of water vapor at 1200 °C in the atmosphere for 1 hour may be used in the production of industrial alloys with low LTEC for objects of special instrument building.