A transformation of this type is said to be athermal, in contrast to one that will occur at constant temperature (isothermal transformation).
These curves also serve another useful purpose because they demonstrate the interrelation between the athermal and isothermal transformations. The intersection of each isothermal curve with the ordinate axis gives the amount of martensite formed on the quench to the holding temperature.
Shakeout and isothermal transformation temperatures have a major influence on the final microstructure.
The isothermal transformation was defined as 90 minutes for all the samples.
The time-temperature dependence of the bainite transformation may also be represented on the
isothermal transformation diagram.
The collective consensus is that the Nakamura model, which relates the
isothermal transformation kinetics to the dynamically cooled crystallization kinetics, is the one that fits the experimental observations best.
Isothermal Transformation Diagrams in a Heavy Section High Alloy Ductile Cast Iron (90-126) D.J.
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Isothermal Transformation Diagrams in a Heavy Section High Alloy Ductile Cast Iron" dealt with the I-T diagrams for heavy section high alloy ductile cast iron (90-126).