Improving ductility of AlSi7Mg alloy by casting-forging process: effect of deformation degree

Abstract

To improve its ductility and clarify the mechanism, the AlSi7Mg alloy fabricated by a novel casting-forging process was solid-soluted at 535 °C for 5 h, followed by aging at 170 °C for 2 h. Phase component, microstructure were observed and mechanical properties were tested. The results show that the alloy contains Al, Si and Al–Si intermetallics. The eutectic Si particles present equiaxed and the Al–Si precipitations present filamentous morphorgy in the alloy. The eutectic Si particles present quasi-continuous network distribution, dividing the matrix into equiaxed units. When the deformation degree increased from 15% to 35%, the units are refined and the precipitation of Al–Si intermetallics is prevented. The difference of ultimate strength between surface and center was decreased, while the elongation improved obviously with the increase of deformation degree. The most excellent elongation reached 12% when the deformation degree was 35%, with the improvement of 7%. The improvement of ductility is owed to the fine, equiaxed eutectic Si particles, the refined units and the prevented precipitations.