Due to a wide range of favourable properties, aluminium alloys found its application in almost all industrial branches. Potential of improving the usage properties has been recognized through forming of favourable intermetallic in mutual interaction of numerous alloying elements such as silicon, copper or magnesium, along with trace elements such as iron and manganese. Other important elements such as titanium, boron, strontium or sodium are intently added through targeted melt treatment in order to improve solidification path by increasing the nucleation potential and therefore changing morphology. Consideration of the casting technology parameters which influence the cooling / solidification rate also represent the base for changing the microstructure and final quality of the casting. Synergy activity of alloying and/or trace elements and theirs interaction and technological parameters of casting process is of great importance in consideration of alloy applicability. This investigation deals with EN AC AlSi12 (EN AC 44100) eutectic alloy with narrow solidification interval, intended for rapid cooling/solidification technology such as high pressure casting (HPDC). Effect of different mode of AlSi12 alloy melt treatment on microstructure and mechanical properties was monitored as a quality insurance. Applied melt treatment mode consists of modification of eutectic with addition of AlSr10 master alloy in all investigated cases. The difference in melt treatment mode was in targeted addition of AlTi5B master alloy. Hypothesis of the examination is based on the assumption that targeted melt treatment can influence the solidification manner, development of microstructural characteristics and finally achieving mechanical properties of the alloy in accordance to corresponded casting geometry and/or technology application.