对定向凝固包晶合金在不同生长条件下, 初生相和包晶相分别作为单相和充分形核相以 低速平界面生长时, 从初始到稳态的整个过渡区间, 两相在界面及界面前沿液相中的 溶质分布进行了分析. 利用充分形核假设和成分过冷准则以及相稳定生长的最高界面温 度判据, 分析了初始过渡区内可能发生的第二相形核转变, 确定了形成带状组织的成 分条件. 考虑到相生长的历史相关性, 将带状组织区分为周期性带状组织区和单一带状 组织区, 更能够对实验现象进行合理的解释. 对Ti--Al合金的计算结果与理论分析一致.
Solute compositional distributions at and ahead of the solid--liquid interfaces are analyzed during the plane--front growth for both the primary and peritectic phases as single phase and nucleation phase for peritectic alloys directionally solidified at low growth rates from initial transient to steady state. Taking the nucleation and compositional undercooling criterion and assuming that the maximum interface growth temperature of phase growth is more stability during the directional solidification, the nucleation transitions during the transient period are investigated and compositional range of band structure formation is determined. Considering the history--dependant growths of a phase, the band structure can be differentiated as cycling band and single band structure, which can explain the experimental phenomena appropriately. The calculated results for Ti-Al alloy are identical with the theoretical analyses.
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