What is grains and grain boundary?

For crystalline materials(rather say polycrystalline), when liquid begin to solidify then the atoms stop moving around much and starts to gather in smaller volume (get packed). read more

A grain boundary (GB) is the interface between two grains, or crystallites, in a polycrystalline material. Grain boundaries are defects in the crystal structure, and tend to decrease the electrical and thermal conductivity of the material. read more

So each grain consists of either a single crystal or polycrystalline aggregate. The surface that separates individual grains from each other are called Grain Boundaries. The crystal orientation changes abruptly across the grain boundry. read more

A grain boundary is the interface between two grains, or crystallites, in a polycrystalline material. Grain boundaries are 2D defects in the crystal structure, and tend to decrease the electrical and thermal conductivity of the material. read more