What happens to the tensile strength of a metal when its grain size is reduced?

When the grain size of a metal is reduced, the tensile strength typically increases due to the phenomenon known as the Hall-Petch relationship. In metals, grain boundaries act as barriers to dislocation movement, which is a primary mechanism of plastic deformation. When the grain size is smaller, there are more grain boundaries present in a given volume of material, which hinders the movement of dislocations more effectively, thereby increasing the overall strength of the metal.

The increase in tensile strength as grain size decreases is particularly significant in metals, as finer grains provide more resistance against external forces that attempt to deform the material. This is particularly relevant in applications where enhanced material strength is crucial, such as in structural components in engineering.

In summary, the reduction of grain size leads to an increase in tensile strength, making the material more robust and better suited for applications requiring high strength.