bainite

Soaking must be long enough to avoid the formation of bainite.

The fraction of bainite that could form increased as the temperature decreased.

The microstructures of martensite and bainite at first seem quite similar.

There are not nearly as many low angle boundaries between laths in lower bainite.

However, in martempering, the goal is to create martensite rather than bainite.

Depending on the temperature, austempering can produce either upper or lower bainite.

The mechanism is not able to explain the shape nor surface relief caused by the bainite transformation.

In normalizing, both upper and lower bainite are usually found mixed with pearlite.

This allows the formation of bainite, an austenite decomposition product.

The resulting bainite steel has a greater ductility, higher impact resistance, and less distortion.

A semi-tempered middle ring of martensite and bainite, and 3.

There is some controversy over the specifics of bainite's transformation mechanism; both theories are represented below.

If cooled even faster, bainite will form.

The temperature range for transformation to bainite (250-550 C) is between those for pearlite and martensite.

This distinction arises from the diffusion rates of carbon at the temperature at which the bainite is forming.

The relief associated with bainite is an invariant-plane strain with a large shear component.

The diffusive theory of bainite's transformation process is based on short range diffusion at the transformation front.

In lower bainite, cementite nucleates on the interface between ferrite and austenite.

Lower bainite is a needle-like structure, produced at temperatures below 350 C, and is stronger but much more brittle.

Under a light microscope, the microstructure of bainite appears darker than martensite due to its low reflectivity.

A fine non-lamellar structure, bainite commonly consists of cementite and dislocation-rich ferrite.

One of the theories on the specific formation mechanism for bainite is that it occurs by a shear transformation, as in martensite.

The steel is then held at the bainite-forming temperature, beyond the point where the temperature reaches an equilibrium, until the bainite fully forms.

Unlike pearlite, whose formation involves the diffusion of all atoms, bainite grows by a displacive transformation mechanism.

Normalized steel consists of pearlite, bainite and sometimes martensite grains, mixed together within the microstructure.