Effect of vanadium on Fe-rich phase, mechanical properties and thermal conductivity of hypoeutectic Al–Si alloy

Abstract In this paper, the effects of element V addition (0, 0.2, 0.4, 0.6, 0.8 and 1.0 wt%) on microstructures, mechanical properties and thermal conductivity of Al–8Si–0.1Cu–0.6Mg–0.7Fe hypoeutectic alloy in gravity die casting process were investigated. Microstructure analysis indicates that the size of Fe-rich phase in the Al–Si alloy is greatly affected by the contents of element V addition. The modification of element V could decrease the length of needle-like β -Fe phase which has the adverse impact to mechanical properties, and promote the formation of short rod-like α -Fe phase which has the favorable effect on mechanical properties and thermal conductivity. Then, the dependencies of mechanical properties and thermal conductivity on the size of Fe-rich phase of the alloy is revealed. When the content of element V is 0.6%, the length of Fe-rich phase in the alloy reaches the minimum, and correspondingly both the mechanical properties and the thermal conductivity could achieve the optimal level, as comparison with other contents of element V addition. However, excessive V addition would form VSi 2 phase and Fe-rich phase with large size, resulting in poor properties of the alloy.