DESIGN OF NEW CASTING ALLOYS OF Al-Mg-Si-Mn SYSTEM WITH ALLOYING ADDITIONS, ITS STRUCTURE AND MECHANICAL PROPERTIES

Abstract

The strength of Al-Mg-Si-Mn casting alloy strongly depends on Mg content in solid solution and precipitation of strengthening phases. Alloys with the nominal composition AlMg5Si2Mn with addition of Li and Ti+Zr were studied by means of differential scanning calorimetry (DSC), transmission electron microscopy (TEM) and energy dispersive X-Ray analysis (EDX). DSC measurements show that the eutectic melting temperature was about 595°C and it is higher than that of commercial A356 casting alloy. The macro- and microhardness tests show that in as-cast state hardness were higher than for A356 and continuously growth during artificial aging. TEM investigations reveal that during artificial aging three different precipitation types are forms in the alloy matrix. Two of them belong to the different structures of Mg 2 Si precipitates. Appearance of the third one identified as d’-Al3Li phase represent that Al-Mg-Si system can be successfully used for designing of Li-containing casting alloy which is not developed yet.