What is the importance of grain size in steel?

It is an established fact that the grain size of the steel has a marked impact on its mechanical properties. Steel with large grain size has lower yield strength, tensile strength, impact toughness, fatigue life and susceptibility to brittle fracture while has better creep resistance.

How does grain size affect metal?

The grain size of a metal or single phase alloy is an estimate of the average grain diameter, usually expressed in millimeters. As the average grain size decreases, the metal becomes stronger (more resistant to plastic flow) and as the grain size increases, the opposite effect on strength occurs.

Does decreasing grain size increase strength?

Decreasing grain size decreases the amount of possible pile up at the boundary, increasing the amount of applied stress necessary to move a dislocation across a grain boundary. The higher the applied stress needed to move the dislocation, the higher the yield strength.

How does grain size affect properties?

Grain size has a measurable effect on most mechanical properties. For example, at room temperature, hardness, yield strength, tensile strength, fatigue strength and impact strength all increase with decreasing grain size. Thus, for example, yield stress is more dependent on grain size than tensile strength [2, 3].

How does grain size affect the ductility of steel?

The ductility decreases sharply as the grain size in a polycrystalline metal is reduced. In nano materials due to grain boundary sliding, ductility increases with decreasing grain size.

How does grain size influence the strength of a polycrystalline material?

The strength of polycrystalline materials is increased by reducing their grain size. Dislocations are more likely to reach a boundary, and thereby strengthen the metal, when the grain size is reduced. 4.19. Effect of grain size on the yield strength of steel.

How does grain size affect toughness?

In toughness mechanism, finer grains tend to obstruct dislocation in a material hence, the smaller the grain size, the better a material withstands dislocation or crack.

Does reducing the grain size of a metal improves its toughness?

In fact decreasing the grain size is the only mechanism by which both the strength and the toughness of a steel is increased. Other mechanisms of increasing strength lead to a decrease in toughness.