Nanoreinforced Cast Al-Si Alloys with Al2O3, TiO2 and ZrO2 Nanoparticles

Abstract

This study presents a new concept of refining and enhancing the properties of cast aluminum alloys by adding nanoparticles. In this work, the effect of adding alumina (Al2O3), titanium dioxide (TiO2) and zirconia (ZrO2) nano-particles (40 nm) to the aluminum cast alloy A356 as a base metal matrix was investigated. Alumina, titanium dioxide and zirconia nano-powders were stirred in the A356 matrix with different fraction ratios ranging from (0%-5%) by weight at variable stirring speeds ranging from (270, 800, 1500, 2150 rpm) in both the semisolid (600 °C) and liquid (700 °C) state using a constant stirring time of one minute. The cast microstructure exhibited change of grains from dendritic to spherical shape with increasing stirring speed. The fracture surface showed the presence of nanoparticles at the interdendritic spacing of the fracture surface and was confirmed with EDX analysis of these particles. The results of the study showed that the mechanical properties (strength, elongation and hardness) for the nanoreinforced castings using Al2O3, TiO2 and ZrO2 were enhanced for the castings made in the semi-solid state (600 °C) with 2 weight% Al2O3 and 3 weight% TiO2 or ZrO2 at 1500 rpm stirring speed.

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

“…%) (Figure 2 a). According to XRD, the powder remaining in the crucible after melting consists of the remnants of metallic W and its oxides of different modifications (WO 3 …”

“…A widespread method influencing the uniform formation of the microstructure and enhancement of strength properties of AlSi alloys is modification of super-and nano-dispersed particles of different chemical compositions [3][4][5][6][7]. The basic nanodimensional modifiers used for silumins are the powders of metal oxide and nitrides [3,4,8].…”

Influence of Modifying Mixtures on Si Crystal Formation in Al-7%Si Alloy

“…In this article, it is shown that the introduction of modifiers leads to a change in the temperatures of basic solidification processes and, accordingly, the morphology of basic structural-phase component materials. At present, a sufficiently large volume of experimental data on the use of metal oxides (γ-Al 2 O 3 , Al 2 O 3 , TiO 2 , ZrO 2 , SrO), carbides (TiCN), borides (Nb-B, Ti-B), carbon-bearing materials (BaCO 3 , C), and their mixtures has been accumulated for modification of the microstructure of primary matrix grains, the eutectic mixture, and precipitations of secondary phases of Al-Si alloys [8][9][10][11][12][13][14]. However, the literature presents ambiguous data on the influence of metal oxides on the microstructure of aluminum-silicon alloys.…”

“…However, the literature presents ambiguous data on the influence of metal oxides on the microstructure of aluminum-silicon alloys. In References [8][9][10][11][12][13][14], it was demonstrated that when modifying mixtures are used, one can observe the refinement of α-Al dendrites, their more uniform distribution, and refinement and change in the morphology of Si crystals in the eutectic mixture, which in turn enables the enhancement of mechanical properties. In Reference [15], the authors explain the influence of P and Sr on the various morphologies of Si particles in alloys of the Al-7%Si type.…”

Effect of ultrafine powders on the structural formation processes and mechanical properties of Al–7%Si alloy

“…Different fluxing agents based on sodium salts, potassium and potassium fluorozirconate (K 2 ZrF 6 ) are mainly used, which provide simultaneous refinement and melt modification, resulting in strong grain refinement [1]. Today, one trend is modification using ultrafine refractory particles [6,7]. When injected into the melt via powder particles, they are absorbed by the melt as a result of their small size and equally spread throughout the volume.…”