Question

Describe the solidification of metals.

Answer 1

Usually liquids have lower energy levels than solid above melting point, owing to which they are more stable than solids. At the melting point both solids and liquids have equal energy, hence they are equally stable. However, below the melting point, the energy of solids is less than that of liquids due to which they are stable. Therefore the liquid gets converted to solids below the melting point during the cooling process. This transformation is termed as solidification.

This transformation or solidification occurs due to nucleation and growth of crystals. At solidification temperature (just below the melting point) atoms from the molten liquid metal start bonding together to form crystals. As the temperature drops, these crystals begin to grow which is known as nucleation. The growth of the crystals happens on account atoms being added progressively at the nucleation point. As the metal solidifies, multiple crystals start growing all over the liquid and start adhering to each other until the entire liquid becomes solid.