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采用基于扩散场理论的宏观相场模型对NiTi形状记忆合金中具有菱方结构的共格Ni_4Ti_3相的析出及长大过程进行了模拟研究;沉淀相的形貌演化通过求解非守恒参量场Ginzburg-Landau控制方程和守恒浓度场Cahn-Hilliard扩散方程获得。与二维模型相比,本研究采用了准确的晶体学参数及改进的数学模型,获得了更为直观及合理的三维盘状变体及二维透镜状变体;Ni_4Ti_3沉淀相的长度、宽度和面积分数随时间的变化分别遵循指数、线性和对数关系;且其长度与宽度的比值并非恒定值,在生长初期该比值有较大的增速而随后逐渐减慢,能很好地解释沉淀相盘状及透镜状形貌特征形成的原因并与相关实验结果吻合。
The macro phase field model based on the diffusion field theory was used to simulate the precipitation and growth of a coherent Ni_4Ti_3 phase with rhombic structure in NiTi shape memory alloy. The morphological evolution of the precipitated phase was solved by solving the Ginzburg- Landau governing equation and conservation concentration field Cahn-Hilliard diffusion equation. Compared with the two-dimensional model, this study used accurate crystallographic parameters and improved mathematical model to obtain a more intuitive and reasonable three-dimensional disc-shaped variants and two-dimensional lenticular variants. The length and width of Ni_4Ti_3 precipitates And the change of area fraction follow the exponential, linear and logarithmic relationship respectively; and the ratio of its length to width is not a constant value, and its ratio increases rapidly at the beginning of growth and then gradually slows down, which can be well explained The reason for the formation of discotic and lenticular morphology of precipitated phase is consistent with the related experimental results.