Complex Structure Modification and Improvement of Properties of Aluminium Casting Alloys with Various Silicon Content

Abstract

The possibility of using complex structure modification for aluminium casting alloys’ mechanical properties improvement was studied. The fluxes widely used in the industry are mainly intended for the modification of a single structural component of Al–Si alloys, which does not allow unifying of the modification process in a production environment. Thus, a new modifying flux that has a complex effect on the structure of Al–Si alloys has been developed. It consists of the following components: TiO2, containing a primary α-Al grain size modifier; BaF2 containing a eutectic silicon modifier; KF used to transform titanium and barium into the melt. The effect of the complex titanium dioxide-based modifier on the macro-, microstructure and the mechanical properties of industrial aluminium–silicon casting alloys containing 5%, 6%, 9%, 11% and 17% Si by weight was studied. It was found that the tensile strength (σB) of Al–Si alloys exceeds the similar characteristics for the alloys modified using the standard sodium-containing flux to 32%, and the relative elongation (δ) increases to 54%. The alloys’ mechanical properties improvement was shown to be the result of the flux component’s complex effect on the macro- and microstructure. The effect includes the simultaneous reduction in secondary dendritic arm spacing due to titanium, the refinement and decreasing size of silicon particles in the eutectic with barium and potassium, and the modifying of the primary silicon. The reliability of the studies was confirmed using up-to-date test systems, a significant amount of experimental data and the repeatability of the results for a large number of samples in the identical initial state.

Casting and Forming of Light Alloys

“…Shlyaptseva et al [2] developed a new modifier with complex effects on the structure of Al-Si alloys. The modifier was composed of TiO 2 , BaF 2 and KF.…”

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

“…Несомненным положительным эффектом модифицирования силуминов титаном является длительность сохранения модифицирующего воздействия. Согласно ранее проведенным исследованиям, титан, введенный с помощью K 2 TiF 6 [20] и TiO 2 [19], при его содержании в сплаве, равном 0,05-0,15 % в зависимости от состава комплексных флюсов, оказывает модифицирующий эффект в течение 5 ч и после нескольких переплавов. Выводы 1.…”

Effect of Si and Holding Time on Ti2Al20La Phase in Al-Ti-La Intermediate Alloy

“…Al-Si alloy is widely used in automotive, aerospace and other industries because of its excellent casting performance, high strength and easy processing [1][2][3][4][5]. However, the coarse α-Al phase and non-uniform distribution of needle sheet eutectic silicon in the ascast condition of conventional Al-Si alloy will cause stress concentration, thereby significantly reducing the mechanical properties of the alloy.…”