散射作用下粒径对激光烧结的影响

采用二维双温度模型对激光烧结过程中的相变传热特性进行了模拟研究,重点讨论了颗粒粒径对烧结过程的影响,在此过程中考虑了散射效应的作用。通过将界面能量平衡方程、成核动力学的界面追踪法相耦合来确定固-液界面的位置。结果表明:当激光垂直照射金颗粒时,熔化现象主要发生在颗粒的两极且底部熔化开始时间早,熔化体积也比较小。颗粒粒径的变化主要影响表面光强分布与传热尺寸两个方面,在激光照射阶段由于散射效应,粒径增加会使颗粒底部光强变强,底部温度升高;在激光照射结束以后,粒径越大,单位光照表面下的传热体积也越大,这导致大粒径颗粒的温度、熔化程度较低,底部温度下降速度更快。

Influence of Particle Size on the Laser Sintering Under Scattering Effects

The phase change heat transfer of a gold particle irradiated by ultra-fast laser was studied by the two-dimensional dual temperature model. The position of the solid-liquid interface was determined by coupledly using the interface energy balance equation and the interface tracking method in nucleation dynamics. In addition, the effects of particle size on the sintering process were studied. The results show that when the laser irradiates the gold particle vertically, the melting phenomenon occurs mainly in the poles of the particle. The bottom of the particle melts earlier than the top and the melting volume is smaller. The difference of the particle size mainly affects the light intensity distribution and the heat transfer size. In the laser irradiation stage, due to the scattering effect, the particle size becomes larger and the bottom light intensity becomes bigger, which raises the bottom temperature. When the laser irradiation has finished, the larger particle size leads to a larger heat-transfer volume, which leads to a decrease in the particle temperature and the melting rate.