二元合金激光快速熔凝过程的非Fourier模型

基于非Fourier定律，建立了脉冲激光加热条件下单相二元合金表面快速重熔和凝固过程的非平衡传热传质模型，并根据碰撞理论和Aziz的连续生长模型处理固／液界面，以解释快速熔凝过程界面动力学的非平衡效应，快速熔凝问题是涉及热质传输的移动界面问题，通过二阶精度的Von Neumann隐式差分格式和界面跟踪方法进行过程模型的数值求解。应用该模型，分析了Al-Cu二元合金的激光表面熔凝过程，结果表明，激光的高能量密度和非平衡界面动力学所引起的熔化过程和凝固过冷对于快速熔凝过程的影响很大，在快速熔凝过程中，界面速度的变化很大，且因基底材料和热流大小而不同，通过计算获得了界面温度，速度、溶质浓度及非平衡分配系数随界面位置的变化，结果显示，在凝固过程中界面速度和界面溶质浓度都存在着很大的波动。

NON-FOURIER MODELING OF SURFACE TRANSIENT MELTING AND SOLIDIFICATION FOR BINARY ALLOYS

Under laser pulse heating, a non-equilibrium heat and mass transfer model based on the non-Fourier law is developed for surface rapid melting and solidification process (RMSP) of Uniphase binary alloys. Non-equilibrium kinetics and Aziz's continuous growth model are introduced in the model to describe the moving solid/liquid interface and to explain the departure from the interface equilibrium thermodynamics. This problem involves heat and mass diffusion with a moving boundary of solid/liquid interface and is solved by an implicit Von Neumann's difference format with second-order precision and interface tracing method. Using this model, we have analyzed laser-irradiated surface melting and solidification of dilute binary Al-Cu alloys. The calculating results show that there are very prominent effects of solid overheating and melt undercooling resulting from the high energy density of laser and interface non-equilibrium kinetics on the process. Large variations of interface velocity are. also seen during the process and depend on the substrate material and heat flux. The interface temperature, velocity, solute concentration and non-equilibrium partition coefficient varying with interface location are calculated. And the fluctuation of the interface velocity and solute concentration during the solidification is also predicted.