Anomalous hardness behaviour of high pressure die-cast mg-al alloys

Abstract

The yield stress (0.2%) of 5 mm thick high pressure die-cast AZ91 and AM60 alloys has been compared to the respective Vickers hardness. The yield stress and hardness were measured in as-cast specimens, and in specimens directly aged (from the as-cast condition) at 120ºC for up to 10000 h. Unlike a range of sand cast and permanent mould cast Mg-Al alloys and an AZ91 alloy, for which the hardness increase proportionally to the yield stress, in high pressure die-cast magnesium alloys the hardness tends to be lower than expected from their yield stress.