We use several aluminium alloys with different mechanical properties and chemical compositions for high pressure die casting parts. The success of the pouring operation depends partly upon certain qualities of the metal itself, for example its composition and temperature, which influences flow, and partly upon properties and design of the mould, including the nature of the moulding material and the gating technique used to introduce the metal into the mould cavity.
The first requirement of aluminium casting alloys is adequate mechanical strength for the intended use. Other important factors are machinability, fluidity (to ensure that within a millisecond the entire cavity with various counters/shapes is filled in without air entrapment, shrinkage which needs detailed thought about air vent position), ability to be surface treated, corrosion resistance, conductivity, leak tightness, appearance and cost. Selection of a particular alloy depends usually on the optimum compromise of all the factors and the intended application.
The production of good castings requires that the aluminium alloys possess favourable properties. Those considered of importance for aluminium alloys are :
• Minimum solidification shrinkage
• Adequate Fluidity
• Minimum difficulty in producing pressure tight castings
• Minimum problem in drosing and gas absorption
• Freedom from hot tearing and cracks