Bainite forms by the decomposition

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.
All time–temperature–transformation (TTT) diagrams consist essentially of two C–curves
(Fig. 1). If we focus first on the Fe–Mn–C steel with the higher hardenability (slower rates
of transformation) then the two curves are separated. The upper C–curve represents the
time required to initiate reconstructive transformations such as ferrite or pearlite, whereas the
lower C–curve represents displacive transformations such as bainite or Widmanst¨atten ferrite.
Notice that as the hardenability of the steel decreases, the two curves tend to overlap so that
in experiments it appears as if the TTT diagram contains just one curve with a complicated
shape, describing all the reactions. This is not the case because it is possible to show that this
is an experimental artifact caused by the inability to detect the two C–curves separately