Impact of anisotropic growth on kinetics of solid-state phase transformation
(State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi’an 710072, China)
Abstract: Based on the statistical analysis of blocking effect arising from anisotropic growth, the anisotropic effect on the kinetics of solid-state transformation was investigated. The result shows that the blocking effect leads to the retardation of transformation and then a regular behavior of varying Avrami exponent. Following previous analytical model, the formulations of Avrami exponent and effective activation energy accounting for blocking effect were obtained. The anisotropic effect on the transformation depends on two factors, non-blocking factor γ and blocking scale k, which directly acts on the dimensionality of growth. The effective activation energy is not affected by the anisotropic effect. The evolution of anisotropic effect with the fraction transformed is taken into account, showing that the anisotropic effect is more severe at the middle stage of transformation.
Key words: transformation kinetics; anisotropic growth; blocking effect; Avrami exponent