**3.3 Shrinkage**

Shrinkage is the natural consequence of liquid to solid transformation of the melt during cooling and is common in most metals. Shrinkage is particularly severe in aluminium alloys. In aluminium alloys, the volumetric shrinkage ranges from 3.5% to 8% (Kaufman and Rooy, 2004). This manifests as shrinkage cavities in larger portions of the casting.

This is often counteracted by strategic placement of risers. Figure 7 shows the typical appearance of volumetric shrinkage defect in an aluminium section.

Fig. 7. Typical appearance of volumetric shrinkage defect in an aluminium section
