Analysis of the stagnant stage in diffusional phase transformations starting from austenite-ferrite mixtures

The stagnant stage during the diffusional phase transformations starting from a mixture of austenite and ferrite has been systematically investigated using local equilibrium diffusional transformation models and the cyclic phase transformation concept. The stagnant stage is identified in M contained alloys (M is substitutional alloying element, and the partitioning coefficient of M between austenite and ferrite is not equal to 1, M = Mn, Ni, Cu, Si), and the length of stagnant stage is affected by the concentration of M and partitioning coefficient. There is no stagnant stage in Fe-C and Fe-Co-C alloys. The length of stagnant stages extends with increasing heating and cooling rate during the cyclic phase transformations. The stagnant stage in quaternary alloys was also investigated, and it was found that the effect of substitutional alloying elements on the length of stagnant stage in multi-component alloys seems to be additive. (C) 2011 Elsevier B. V. All rights reserved.