Physical Metallurgy of Aluminium Alloys

Aluminium is a soft and weak and is strengthened by alloying with suitable elements. The elements which are added to aluminium in appreciable quantities to increase its strength are limited to only four elements namely magnesium, silicon, copper and zinc.
These may be, added singly or in combination. It will
be Seen that the alloying elements magnesium and silicon
belong to aluminium period itself while the copper and
zinc metals belong to the copper period in the periodic
table. Out of these foux elements magnesium has biggAr
atomic diameter (3. 1906 A) than aluminium (d = 2.857 A),
while silicon, gopper and zinc have smaller diameters,
2.345 A, 2.551 A and 2.659° respectively. These values
are within 15% of the aluminium diameter values.
Therefore these alloying elements are favourably placed
fer- forming. Substitutional solid solutions with
aluminium.