Influence of soaking time of modifier in melt on microstructure of Al-12%Si alloys

The influence of the soaking time of the silumin melt with a modifying nanopowder W on the microstructure and the impact toughness of the Al-12%Si silumin is studied in the paper. It was established that when introducing 0.1 mass. % of W and soaking it for 10 min, up to 30% of the inassimilable nanopowder W remains in the crucible after pouring. At that, the microstructure of castings is refined, and the impact toughness increases by 12 % compared to the initial alloy. It was established that the powder remaining in the crucible after melting consists of the remnants of metallic W, WO₃ and W₃O. Nanopowder W is completely assimilated by the melt if the soaking time is increased by 120 min; in this case, the impact toughness reduces, which is connected with the increase of dendrites and silicon wafers sizes.