When Does Bainite Form?

Bainite forms by the decomposition of austenite at a temperature which is above MS but below that at which fine pearlite forms. All bainite forms below the T0 temperature.

How bainite is formed during part of continuous cooling?

Austenite that is cooled sufficiently rapidly to avoid higher temperature transformations, can form martensite, without any diffusion of either iron or carbon, by the deformation of the austenite's face-centred crystal structure into a distorted body-centred tetragonal or body-centred cubic structure.

Which phase of the following is present in bainite?

Bainite is a mixture of two phases: ferrrite and cementite. It can contain the retained austenite, if temperature of austenite decomposition was siuifficiently low.