Definition - What does Grain Growth mean?
Grain growth refers to an increase in the size of crystallites (grains) in a material at high temperatures.
Grain growth is due to an alteration of the internal energy of the molecular structure of a given metal, ceramic or mineral. Grain growth is typical in metals that have undergone annealing and other processes of surface modification. Due to the destabilization of the molecular structures of metals due to grain growth, the probability of crevice, intergranular and grain boundary corrosion are increased.
Corrosionpedia explains Grain Growth
A grain is a piece of a single crystal. One grain may grow by absorbing atoms from neighboring grains. Grain growth is driven by a reduction in the total energy of the system and results in reducing the grain boundary surface area. When some grains grow, the total number of grains in the material decrease, thus reducing the free energy of the system.