In what manner are the pressures exerted on metals typically altered by their grain size?

The relationship between grain size and the mechanical properties of metals is crucial in understanding material behavior under stress. When considering how grain size affects the pressures exerted on metals, one of the key concepts is that the presence of larger grains can indeed affect a metal's ability to resist deformation.

Larger grains in metals do lead to a situation where there's reduced interference between dislocations, which are defects in the crystal structure of metals that contribute to deformation. This reduced dislocation density means there’s generally a higher resistance to deformation when subjected to constant loads. In contrast, materials with a fine-grained structure exhibit increased strength and hardness because the smaller grains create more grain boundaries that obstruct the movement of dislocations, ultimately making the material harder to deform under applied stresses.

In summary, larger grains, while presenting less resistance to the motion of dislocations, can lead to higher resistance to deformation under certain conditions, particularly when a constant load is applied. This relationship is well established in material science and explains why metals with larger grains tend to demonstrate different mechanical behaviors when compared to those with finer grains.