EFFECT OF NaNO3, NaClO3 AND TiO2 ON MECHANICAL PROPERTIES AlSi7Mg ALLOY

Abstract

Hypo-eutectic silumins are used in a wide range of industrial applications, but their properties are continuously studied to improve the quality of cast products. The initial structure of AlSi9Mg alloy is composed of granular and acicular β phase, with α phase as matrix. The hard, irregular, often pointed β phase is responsible for the poor mechanical properties of said alloy. This composition is responsible for the alloy's low strength parameters, and it limits the extent of practical applications. The properties of alloys may not only depend on the chemical composition, modifiers, but may also depend on the conditions of the modification effect. Chemical elements and compounds, both added to the alloy and formed as a result of exothermic reactions, “pass” into the alloy, changing the course of its crystallization. Selection of the mixture components allows – to a degree – to decide about the starting moment of crystallization and change the range of alloy solidification or its individual phases. In the present study, the microstructure and technological properties of silumins were improved through modification with the use a chemical mixture as an exothermic modification. It was found that the exothermic modifier containing NaNO 3 NaClO 3 and TiO 2 exerted the strongest multidirectional refining effect on the studied alloys.