The Influence of the Proportions of Titanium and Boron in the Al and AlSi7-Based Master Alloy on the Microstructure and Mechanical Properties of Hypoeutectic Silumin, AlSi7Mg

Unmodified hypoeutectic silumins have a microstructure composed of large-sized phases, which are the reason for their low mechanical properties. Many years of research have shown the modifying effects of many chemical elements and their compounds, including the master alloy consisting of Al-Ti-B, often in the form of the finished AlTi5B alloy. In this work, it was decided to check how the proportions of Ti and B content in the Al or AlSi-based master alloy affect the microstructure and mechanical properties of a hypoeutectic silumin, AlSi7Mg. It has been shown that a master alloy containing silicon (with the participation of Al + Ti + B) has a more effective impact on the refinement of the microstructure, and thus an increase in the mechanical properties of the AlSi7Mg alloy, than a master alloy without silicon. It has been shown that the ratio of titanium to boron content in the very-often-used AlTi5B modifier is not always optimal. It has been shown that the use of a master alloy with a composition similar to that of modified silumin with titanium and boron in a 2:1 ratio allows the obtaining of an AlSi7Mg alloy with higher mechanical properties than the alloy after the modification of the AlTi5 master alloy.