Effect of V addition on the nano-size spherical particles growing on the Fe-bearing intermetallics and silicon phases of gas atomized hypereutectic Al–20Si–5Fe alloys

Abstract

In this study, rapidly solidified hypereutectic Al–20Si–5Fe–XV (X=0, 0.5, 1 and 1.5) alloys were fabricated by gas atomization in Ar atmosphere. Microstructural and spectroscopic analyses were performed using SEM, SEM – EDS and XRD measurements. Experimental results showed that addition of V to gas-atomized Al–20Si–5Fe alloys led to formation of a refined microstructure composed of finer Si and Fe-bearing intermetallics. Possible refining mechanism of Si phases is the IIT because of Rv:RSi is 1.38 close to the value of 1.65 which is the ideal ratio of radius for the impurity-atom to Si-atom (Ri:RSi). The reason of formation finer of δ-Al4FeSi2 phase with addition of V is that vanadium addition leads to an increment in the thermodynamic stability and a reduction in the free energy of δ-Al4FeSi2 phase. Therefore, finer and modified morphology became more favorable for δ-Al4FeSi2 phase in terms of thermodynamic. Nanosize Si particles growing on the surface of Fe-bearing intermetallics and micro size polygonal Si phases were observed. There was no effect of V on the number of fine silicon particles growing up on the micro size polygonal Si phases. However, during solidification, addition of V led to an increase in the number of fine silicon particles growing on the Fe-bearing intermetallics. Microhardness measurements showed that there was an increase in the microhardness values of Al–20Si–5Fe alloys with addition of V, in general.