Effect of Composition and Thermal Treatment on the Natural Ageing of Aluminium -Zinc-Copper Alloys

THE aluminium-zinc-copper alloy designated BS L5 was one of the first aluminium casting alloys used in the United Kingdom. The first specification was issued before or during the First World War and for many years the alloy was widely used for the production of sand castings for the automotive industry, e.g. engine sumps and blocks. With the introduction of the aluminium-silicon and aluminium silicon- copper alloys, which had superior casting properties, the use of alloys of the BS L5 type declined.
The L5 specification permitted the use of virgin
materials only, but during the 1939-45 War, an emergency
specification was introduced which permitted the use of' secondary materials. This specification, designated LAC 113, was later superseded together with BS L5, by the General Engineering+Specification BS 1490, LM. 3.