Issues in determining teh phase transofrmation kinetics from TTT diagrams

摘要

Phase transfromation kinetics is the core of any effort trying to study the microstructure,properties,or even the distortion in heat treated ocmponents.In this paper,we first re-examine the theory of nucleation and growht of diffusive solid phase transfomratin at constant temepratures.The general formulation is simplified to show that the isothermal transformation kinetics are characterized by several parameters,i.e.,incubation time,rate constant,shape factor,and activation energies.For practical applications,it is desirable to determine these parameters from the generally available TTT diagrams.In this study,we examine issues in determining these parameters The bainite transfromations of a high carbon,high chromium bearing steel is useed as the model process.The theory is demonstrated by the excellent agreement between the calculated and the measured transformation.