等温马氏体转变动力学模型的修正

Revised Kinetic Model of Isothermal Martensitic Transformation

自促发形核机制对于等温马氏体转变的解释是正确的.但是现有几种动力学模型尚存在一些不妥之处.文中给出一种物理意义更为明确的修正模型.

Pati and Cohen revised the dynamic model of Entwisle and Raghavan [1] concerning isothermal martensitic transformation. Then, Pati and Cohen obtained a revised expression for the number of embryos N_: N_1=(N_i+pf-N_v)(1-f)[2,3]. One contribution of this paper is the further revision of Pati-Cohen's model and the derivation of a new expression for N_i: N_t=(N_i+pf)(1-f). Another Contribution of this paper is the author's conclusion that p, in the new expression for N_i, is a variable. These two contributions enable the authors to obtain computed results that are in better agreement with Pati and Coheir's experimental data than their own computed results [3]. Some additional explanatory remarks about the authors' contributions will now be offered. In Pati and Cohen's formula N_1=(N_i+pf-N_v)(1-f), Pati and Cohen deemed that pf(1-f) is the total number of embryos produced by autocatalytic ect. The authors are of the opinion that Pati and Cohen's view about the physical meaning of pf(1-f) is imperfect and made necessary revisions to obtain the new expression N_i=(N_i+pf)(1-f). Pati and Cohen took p as constant. The authors are of the opinion that, from intrinsic-quality of autocatalytic effect, p should be related to increment of free energy of system AG, and according to the law of energy conversion, △G decreases during transformation gradually. Thus it can be concluded that p must be a variable. Fig.3 shows experimental data (solid curve) compared with Pati and Cohen's computed curve. It can be seen that, for the volume fraction of martensite higher than approximately 15%, the computed curve deviates from experimental data. Fig.4 shows experimental data (solid curve) compared with the authors' computed curve. It can be seen that the agreement is much better than that of Fig.3 when the volume fraction of martensite is higher than approximately 15%.