Abstract
The effects of alloying elements on the kinetics of austenitization from pearlite structure were studied by computer simulation in Fe–C–M ternary alloys, where M is Mn, Cr, Si or Ni, assuming local equilibrium conditions at all transformation interfaces. A thin austenite film was assumed to nucleate at ferrite/cementite interfaces and grow in one dimension. The existence of a partition to no-partition transition temperature (PNTT) was rationalized. Above the PNTT, the growth rate of austenite is governed by the difference in carbon activity between austenite/cementite and ferrite/austenite interfaces; a substitutional element influences the reaction rate by affecting carbon activity. Below the PNTT, redistribution of M is necessary. The PNTT increases with the concentration of all alloy elements except Ni, which has a large segregation tendency in austenite from both ferrite and cementite, as well as repulsive interaction with carbon. The amount of overheating at PNTT from Ae1 increases in the order Si (∼Ni), Mn and Cr, essentially in agreement with a recently reported experiment.
Acknowledgements
The authors express their thanks to CISRI-TCS United Open Laboratory, Beijing, for assistance in calculation. The support from the National Natural Science Foundation of China (Grants 51071089 and 51171087) is gratefully acknowledged.