
276 Engineering Materials Technology
alloy has the composition 0.7 per cent magnesium, 1.0 per cent silicon and 0.6
per cent manganese. This alloy is not as strong as the duralumin but has greater
ductility. It is used for ladders, scaffold tubes, container bodies, structural
members for road and rail vehicles. The heat treatment is solution treatment at
510°C with precipitation hardening by quenching followed by precipitation
hardening of ten hours at about 165°C. Another group of alloys is based on
aluminium-zinc-magnesium-copper, e.g. 5.5 per cent zinc, 2.8 per cent
magnesium, 0.45 per cent copper, 0.5 per cent manganese. These alloys hav ...