金属快速凝固的非平衡超急速传热模型

TRANSIENT HEAT TRANSFER MODEL FOR RAPID SOLIDIFICATION OF METALS

运用非Fburier传热理论建立了金属快速凝固过程中的非平衡传热理论模型,包括非Fourier方程的建立、传热与相变模拟.模拟计算表明: (1)在溅射激冷条件下,界面换热系数越大,界面冷却速度和移动速度也越高.在界面换热系数相同时,计算得到的界面冷却速度随着固-液界面高度的提高呈现先上升而后下降的变化趋势;计算得到的冷却速度值明显小于Fourier定律的计算值. (2)在激光加热条件下,计算的界面移动速度在凝固开始时先急剧增加,然后渐趋平稳.计算还表明,金属的过热度及过冷度与其热物性相关.

Based on the non-Fourier heat transfer theory, non-equilibrium theoretical models during rapid solidification process (RSP) of metals are put forward and simulations are done for melt spinning of pure aluminum and laser surface remelting and solidification of pure nickel and aluminum, which include establishing the non-Fourier equations of the processes, non-Fourier simulation of heat transfer and phase transformation during the processes. Simulation results show that RSPs of the metals is within the range of transient heat transfer and the non-Fourier effects can be characterized by the non-Fourier heat transfer modes: (1) When a droplet falls on the surface of a running roller under the condition. of melt spinning, the larger the interface heat transfer coefficient, the faster the interface cooling rate and interface velocity. When the interface heat transfer coefficient is the same, with the solid/liquid interface elevation, the interface cooling rate increases and then decreases, which is different from that obtained by Fourier model. In addition, the calculated cooling rate is less than that by the Fourier model; (2) Under the condition of laser heating, the solid/liquid interface velocity increases rapidly and then becomes slow. The simulation results also show the superheating and undercooling of the metals are related to their thermophysical properties.