Effect of magnetic stirring, grain modification and refinement on the solidification structure of an A356 aluminum alloy

Abstract

The effect of the application of forced convection during the continuous solidification of Al-Si alloys has been presented in this work. The investigation has been made on the hypothesis that as an alloy solidifies under the action of a rotating magnetic field, a nondendritic casting structure would be obtained. The Al-Si alloy has been studied in its three different states (original, modified, and modified with a grain refiner), using a magnetic stirring equipment with permanent magnets, a device that has allowed the study of the effect of the rotational speed (degree of stirring) on the micro-and macro-solidification structure, as well as on the material's mechanical properties. With the purpose of validating the hypothesis, different analyses and tests have been carried out, such as thermal analysis of the solidification process, micro-and macrostructural analysis, and hardness measurements for the different process conditions studied. The results have shown that magnetic stirring affects the cooling curves, expanding the solidification range. A microstructural evolution of the alloys has also been observed, from a 100% dendritic structure to a mature rosette type structure, in addition to a notable decreasing of grain size, which results in the improvement of the material's mechanical behavior.

Effect of magnetic stirring on AlFeSi intermetalics of an A356 aluminum alloy

“…Hypoeutectic Al-Si alloys as A356, once solidified, have basically two micro-constituents: one with low hardness and ductile, primary α-Al solid solution, and an eutectic that consists of α-Al and Si needles (with high hardness and fragile), where the α-Al acts as a matrix for the Si phase. This eutectic has the particularity of being irregular, because it incorporates the characteristics of the solid solution high in aluminum and Silicon, which is practically insoluble, so its mechanical behavior is directly related to the shape, size, and distribution of Si [16][17][18].…”

“…However, ripening processes obtained for the reduction of the surface area will operate and the regions of high curvature will be eliminated or reduced by diffusion of solute in the liquid. Ripening can be accelerated by increasing stirring since this increases solute transport [18].…”

Thermal analysis of modified segmented switched reluctance motor with aluminium metal matrix composite fins used in cooling fan applications

“…Choosing a suitable fin material and type of fin arrangement plays a crucial role in the effective thermal management of the SRM. There are numerous materials used for such applications reported in the literature [25][26][27][28][29][30]. Among these Aluminium metal matrix composite materials have attracted more interest in recent times.…”