2020 – 12 – Crystal Growth

While solid metals contain very particular crystal structure, a metal in a molten state has a random arrangement instead of a crystal structure.
As molten metal cools, small seed crystals will form in the areas that are coolest. As the temperature falls, the crystals grow by attracting other atoms from the liquid metal.
Crystals will continue to grow until they are stopped by the grain boundaries of other crystals. The rate at which crystals grow is called its nucleation rate, which is related to the time passed and temperature lost.