As a result of the transformation, the microconstituents, Pearlite and Bainite, form; Pearlite forms at higher temperatures and bainite at lower.
22.
Most alloying elements will lower the temperature required for the maximum rate of formation of bainite, though carbon is the most effective in doing so.
23.
Bainite occupies a region between these two process in a temperature range where iron self-diffusion is limited but there is insufficient driving force to form martensite.
24.
"' Bainite "'is a plate-like microstructure that forms in steels at temperatures of 250 550 �C ( depending on alloy content ).
25.
This is possible provided the cooling rate is such that the cooling curve intersects the martensite start temperature or the bainite start curve before intersecting the P s curve.
26.
Typical austempering process parameters applied to an unsuitable material will not result in the formation of bainite or ausferrite and thus the final product will not be called austempered.
27.
In steel it produces a bainite microstructure whereas in cast irons it produces a structure of acicular ferrite and high carbon, stabilized austenite known as " ausferrite ".
28.
For instance, in the iron-carbon system, the austenite phase can undergo a eutectoid transformation to produce ferrite and cementite, often in lamellar structures such as pearlite and bainite.
29.
In contrast to pearlite, where the ferrite and cementite grow cooperatively, bainite forms by the transformation of carbon-supersaturated ferrite with the subsequent diffusion of carbon and the precipitation of carbides.
30.
A further distinction is often made between so-called lower-bainite, which forms at temperatures closer to the martensite start temperature, and upper-bainite which forms at higher temperatures.
