Casting is one of the main routes for producing aluminium-alloy parts. Good castability for foundry alloys includes a relatively high fluidity, low melting point, short casting cycles, relatively low tendency for hot cracking, good as-cast surface finish and chemical stability. In hypoeutectic alloys, it is common to refine the size of the aluminium crystals by grain refinement for applications requiring good mechanical properties. In Al-Si alloys, a treatment called eutectic modification is often used to change the eutectic silicon from coarse platelike into fine fibrous morphology, which is less harmful to mechanical performance. Main shape casting processes include high-pressure die casting, low-pressure die casting, permanent mould casting and sand casting. Each process has its own strategy for filling the alloy into the mould/die and feeding the solidification shrinkage.