GB634492A - Improvements in or relating to aluminium-base alloys - Google Patents

Abstract

An aluminium base alloy containing also only magnesium and zinc has a content of magnesium which is not greater than 14 per cent and not less than 9 per cent, and a content of zinc less than 2 per cent and greater than an amount ranging between 0.4 per cent for alloys containing 14 per cent of magnesium and 0.8 per cent for alloys containing 9 per cent of magnesium. The alloy is homogenised at a temperature as close as possible to 450 DEG C for the homogenisation to be rapid, e.g. for 8 hours, preferably in the absence of air and water vapour, e.g. in an inert atmosphere of dry hydrogen or argon, or in a mixture of fused salts, e.g. chloride or fluoride salts. The alloy is then quenched in hot water or in oil and hardened at room temperature or by heating at temperatures below 175 DEG C. In the Specification as open to inspection under Sect. 91 the composition of the alloy ranges between an upper limit of zinc of less than 3 per cent and a lower limit which is greater than 0.4 per cent with 14 per cent magnesium and is greater than 1 per cent with 8 per cent magnesium, the balance being aluminium, except for an optional addition of 0.3-0.6 manganese. A suitable alloy has a composition of magnesium 12 per cent, zinc 2 per cent, manganese 0.4 per cent, the balance being aluminium. This subject-matter does not appear in the Specification as accepted.