Effect of heat treatment and artificial ageing on Al-5Mg-2Zn

Abstract

Traditionally aluminium casting alloy 513 is not heat treated after permanent mould casting. Al-Mg alloys are generally not heat treatable but the higher Zn content in this alloy could render it heat treatable. It could be expected that in its as-cast state (F temper condition) there should be non-equilibrium intermetallics remaining at grain boundaries after casting which could be detrimental to corrosion properties of the alloy. This study investigated the effect of heat treatment and artificial ageing of Al-5Mg-2Zn. The study showed intermetallic phases at the grain boundaries and a melting peak at about 476 °C for the F condition. Solution heat treatment at 440°C for 4 hours dissolved the intermetallic phase thus increasing the melting point of the alloy. The results further showed an appreciable increase of mechanical properties after T6 heat treatment over the F-condition.