Aluminium Alloys

Duralumin.

It contains 4% Cu, 0.5% Mg, 0.5% Mn and the rest aluminium. It has high tensile strength, comparable with mild steel, combined with the characteristic lightness of aluminium. It, however, possesses a low corrosion resistance. To improve upon the same, a thin film of Al is rolled on the duralumin sheets. These sheets are known by their trade name Alclad, and are widely used in aircraft industry. It is available in various forms like bars, tubes and sheets. In its wrought form it can be cast, forged and stamped easily. It can also be age hardened.

Aluminium casting alloys

A general purpose casting alloy contains 90% Al, 8% Cu, 1% Si. It has good strength, hardness and machinability. It may be sand, gravity or pressure die cast. Another general purpose aluminium casting alloy consists of 13.5% Zn, 3% Cu and the remainder Al. Similarly, a large number of aluminium casting and forging alloys have been developed in the recent past which possess fairly high strengths.

Al-Si alloy contain 5 to 15% Si and the rest Al. They have good castability, low shrinkage, and the castings made from them are quite sound. A more refined structure of casting is obtained by adding a small amount of sodium.

Y-Alloy

It contains 93% Al, 4% Cu, 2% Ni and 1% Mg. Its principal use is as a casting alloy. It maintains its strength at elevated temperatures, and is used for pistons of I.C. engines. A heat treatment of Y-alloy castings, consisting of quenching in boiling water from a temperature of 5100 C and then aging for 5 days, develops very good mechanical properties in them. It is also used in strip and sheet forms.