Use of Computer Simulations to Analyze Limitations of Kinetic Models for Recrystallization.

摘要

Only two kinetic models appear to be appropriate for recrystallization of metals and crystallization of metallic glasses: Kolmogorov-Johnson-Mehl-Avrami (KJMA) and Speich-Fisher (SF). However, much confusion prevails on the proper use of these models because their limitations are not well understood. Fortunately, computer simulations are proving to be effective for simulating kinetic behavior. In particular, a simplified computer model, which simulates a regular geometric grain growing in an impingement cell, provides kinetic simulations that agree with experimental data. The computer model isolates specific concepts that the kinetic models were formulated on, and it also simulates different time-dependent growth relations. The KJMA model is based on linear interfacial growth and uses an extended-volume concept to compensate for impingement. The computer model isolated the effect of the extended-volume concept, and it also was used to determine why some experimental data conform to KJMA kinetics while others do not. The analysis indicated that essentially linear KJMA behavior can occur in recrystallization of metals that have reached an effectively constant state of recovery or in crystallization of amorphous metals that have reached a constant state of disorder. The SF relation is based on inverse-time-dependent growth, and it is effective for recrystallization that is retarded from an initial linear rate by factors such as the simultaneous occurrence of recovery. The computer model clearly defines the limitations of the SE model. This work demonstrates that computer simulations can define the limitations of the existing kinetic models and increase our understanding of them. 24 refs., 1 fig.