激光毛化的温度场和熔化过程流动状态的变化,以及因辅助气体等导致的对流换热边界条件变化都会对材料表面成形质量和组织转变产生重要影响。于是建立了模拟激光毛化的三维瞬态模型,该模型考虑了热传导、对流传热及熔池表面的形貌变化等因素,采用焓法与流体体积(VOF)方法处理固液相变移动边界与自由表面的问题,利用Fluent软件和用户自定义函数(UDF)方法求解,处理了辅助气体的驱动作用及自由表面和相界面的演化,得出了脉冲激光毛化过程中各种加工参数下熔池的形状、大小以及熔池内的温度、速度分布。实际毛化加工结果与数值模拟结果基本一致。

The temperature field, molten flow and gas jet induced convection and heat exchange boudary conditions are important for material surface formation quality and tissue transformation in laser texturing. Then a three-dimensional transient numerical model is developed for the heat transfer, convection heat transfer and morphology evolvement of the molten pool during laser surface texturing. Based on the software Fluent, the model adopts the enthalpy and volume of fluid (VOF) methods to solve the solid-liquid phase boundary and free surface flow numerically. The evolution of phase interface and free surface, and the effect of assist gas on the surface profile are analysed. The heat transfer and fluid motion, as well as the surface shape and scale of the molten pool are numerically approached for the pulse laser texturing with different processing parameters. The numerical simulation was consistent with the result of laser texturing experiments.