Which material property is influenced by grain boundaries?

Grain boundaries play a significant role in determining the mechanical properties of materials, particularly strength. When a material is composed of individual grains, the interfaces between these grains (the grain boundaries) can impede the movement of dislocations, which are defects in the crystal structure that facilitate plastic deformation. This obstruction occurs because dislocations tend to get 'stopped' by the grain boundary, effectively making it more difficult for the material to deform under stress.

As a result, a material with a finer grain structure will generally exhibit increased strength due to the higher density of grain boundaries that inhibit dislocation movement, a phenomenon described by the Hall-Petch relationship. This enhancement in strength with decreased grain size is foundational in materials science and engineering.

While the other properties mentioned, such as electrical conductivity, corrosion resistance, and thermal resistance, may also be affected by grain boundaries, their influence is not as direct or significant in terms of mechanical strength. For example, grain boundaries can act as barriers to electron flow in metals, potentially affecting electrical conductivity, but this effect does not correlate in the same way to mechanical strength. Therefore, while all these properties can be influenced by grain boundaries to some extent, strength is the most significant and direct effect observed in relation to grain boundaries.