建立了界面反应-扩散混合控制模型用于描述先共析铁索体的台阶生长过程.考虑C原子长程扩散和界面反应对铁索体生长的共同控制作用,建立了混合控制机制下先共析铁索体生长动力学的理论模型.运用该模型对先共析铁素体的台阶生长过程进行了模拟,提出了决定先共析铁素体生长机制的控制因子S.S因子包含了碳扩散,界面迁移、相变温度以及成分的作用.通过该因子可判别是C原子长程扩散还是界面反应在先共析铁索体生长中起主导作用.当S较小时,铁索体生长以界面控制为主;当S较大时,铁素体的生长以扩散控制为主.对Fe-1%C(原子分数)合金在720℃的等温,γ→α转变进行了模拟,所得结果与文献报道的实验结果符合较好.
A mixed control model considering both carbon diffusion and interracial reaction is established for ledgewise growth kinetics of proeutectiod ferrite during γ→α isothermal transformation in low carbon steels. In this model, the growth rate of ledgewise ferrite and the carbon concentration at the ledge riser are determined by both carbon diffusion at ledge riser in austenite and interfacial reaction rate of γ→α transformation, which is different from the traditional local equilibrium(LE) model. Simulation is done by utlizing this model to analyze the ledgewise growth kinetics of proeutectiod ferrite. And based on analysis of the characteristics of growth kinetics of proeutectiod ferrite obtained by the simulation, a factor S, which includes the effects of carbon diffusion, interface migration, temperature and composition, is proposed to characterize the control mode of growth kinetics.By judging this factor S, we can predict that if the carbon diffusion or interfacial reaction dominates the growth kinetics of proeutectiod ferrite. In the case that the value S is relatively small, the growth kinetics is mainly controlled by interfacial reaction. In the case that the value of S is quite large, the growth kinetics is controlled by carbon diffusion, which returns to the traditional local equilibrium model. The mixed control simulation results for ledgewise growth of proeutectoid ferrite at 720 ℃ in Fe-1%C (atomic fraction) alloy show a good agreement with the experimental results previously reported.
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