γ → α transformation in Fe, Fe–Ni, and Fe–Cr alloys

Kinetics of solid state phase transformations: Measurement and modelling of some basic issues

“…There is one evidences in metallurgical literature, which suggest that on rapid heating or cooling conditions, classical nucleation and growth mediated phase changes are inhibited and yield way to martensitic or displacive types. 6,7 From the experimental point of view, the heating or cooling rate dependence of transformation temperatures, in addition to the transformed fraction X(T), offer a valuable wholesome kinetic data set. It is generally the case that the transformation temperatures are highly nonlinear with respect to heating or cooling rate, and this tendency is exhibited more remarkably by the transformation finish (T f ) temperatures.…”

“…(dX/dt) = f (X)k(T), (6) f (X) is an empirical reaction model and k(T) is the rate constant as mentioned before. But such a separable representation is conceptually incompatible with the basic premise of isochronal transformation kinetics, 16 despite the fact that they are extensively patronised in data analysis, basically because of their simplicity.…”

Observation of .GAMMA..RAR..ALPHA. Transformation in Ultralow-carbon Steel under a High Temperature Optical Microscope.

“…The F s temperature falls with an increase in cooling rate and is in the range from 845 to 813°C. The relationship between cooling rate and g→a transformation temperature has so far been examined by many researchers: Gilbert and Owen, 14) Bibby and Parr, 15) Izumiyama et al, 16) Ackert and Parr, 17) Morozov et al, 18) Leslie, 9) Wilson 19,20) and Mirzayev et al 21) According to their results, the transformation temperature decreases as the cooling rate increases in the range of relatively slow cooling. Beyond the critical cooling rate, the transformation temperature becomes constant and shows some plateaus on the F s versus cooling rate curve.…”

Microstructural characteristics of Al-alloyed austempered ductile irons

“…However, it is expected that higher austenitising temperature and times both lead to an increase in the austenite grain size [3,11,12]. Thus, it is believed that with reduction in the unit area fraction of grain boundaries the nucleation tendency of bainitic ferrite can be decreased so that transformation may be suppressed at lower cooling rates [13,14]. The transformation during austempering ductile cast iron can be considered in two stages [15].…”