Influence of various titanium-containing additives on the modification efficiency of aluminum–silicon eutectic alloy

Abstract

This study investigates the impact of titanium addition to the eutectic silumin AK12 melt, considering various methods of addition. The research results encompass the sole introduction of titanium (at a calculated amount of 0.1 wt.%) through different forms/methods, such as the Al–4%Ti ligature, TiO2 oxide, K2TiF6 salt, and Ti sponge. Additionally, the study explores the combined addition of titanium and a standard flux (comprising 62.5 % NaCl + 12.5 % KCl + 25 % NaF). The research involved qualitative and quantitative analyses of macro- and microstructures, spectral analysis data, and mechanical properties (tensile strength and relative elongation) of the alloys. The findings highlight that titanium has a positive influence on the structure of eutectic silumin, with the most effective results achieved when combined with the standard flux. However, the efficiency of silumin modification with titanium varies depending on the method of addition. Specifically, the introduction of titanium in the form of K2TiF6 fluoride salt, Al–4%Ti ligature, and titanium sponge positively affected macro grain refinement, reduced the spacing between the secondary dendrite arms of the solid solution (α-Al), and enhanced the dispersion of eutectic silicon. The most promising approach for complex silumin modification involves the joint introduction of titanium-containing substances and a sodium salt-based flux. This combination has a multifaceted impact on the silumin structure, leading to the simultaneous modification of various structural components in aluminum–silicon alloys. Depending on the type of titanium-containing substance, when processed alongside flux, the alloy achieves a relative elongation ranging from 9.7 % to 11.1 %, exceeding the same parameter for the unmodified alloy by more than 4 times and surpassing the sodium-modified alloy's relative elongation by 17–37 %. Furthermore, the ultimate strength reaches levels of 171–193 MPa, representing a 22–38 % improvement compared to the unmodified alloy and a 7–21 % increase compared to the sodium-modified alloy.