Microporosities and internal cracks
Solidification — Macrostructures and product quality

Microporosities, also known as microretentions, appear when the residual interdendritic liquid trapped between several neighboring crystals solidifies. As the resulting contraction cannot be compensated for by a supply of liquid metal, small cavities are formed, lined or woven by the dendrites already in place. Microporosities are difficult to detect using non-destructive methods (X-rays), and are usually only visible on polished sections under a microscope.

The origin of cracks must be clearly distinguished from that of microporosities: in the first case, it's a question of stresses or deformations imposed on the solid tissue, usually dendritic 4.4