辅热对纳秒脉冲激光作用铝合金蒸气反冲压的影响研究

The Study on the Influence of Auxiliary Heating on the Recoil Pressure of Aluminum Alloy Vapor Induced by Nanosecond Pulsed Laser

摘要: 当较低能量密度的纳秒激光照射靶材表面时，激光能量被吸收，导致瞬时的温度升高。当靶材表面温度升高至熔点时，金属开始熔化，形成液态相。当纳秒激光能量足够高时，会引起金属的蒸发，这种蒸发会导致金属材料的损失和去除。同时金属由于强蒸发会产生蒸气反冲压力。当过热液体温度上升至0.9 Tc (Tc为热力学临界温度)时，达到相爆炸阈值，过热液体内部开始均匀地形成微小的气泡核，这最终导致了相爆炸的发生。本文基于激光烧蚀金属靶材理论，建立辅热下纳秒脉冲激光烧蚀铝合金的数值计算模型，计算分析不同辅热温度下，纳秒激光烧蚀铝合金的蒸气反冲压力。结果表明：在辅热下的高温靶材对激光的吸收率较高，导致较低能量激光就可以使靶材达到熔融和气化过程，提高了纳秒脉冲激光的能量利用率，增强了激光诱导表面饱和蒸气压和蒸气反冲压。

Abstract: When the surface of the target material is irradiated by a nanosecond laser with relatively low energy density, the laser energy is absorbed, resulting in an instantaneous temperature rise. As the surface temperature of the target material increases to its melting point, the metal begins to melt, forming a liquid phase. When the nanosecond laser energy is sufficiently high, it causes the metal to evaporate, resulting in the loss and removal of the metal material. At the same time, the strong evaporation of the metal generates vapor recoil pressure. When the overheated liquid temperature rises to 0.9 times the critical temperature (Tc, the thermodynamic critical temperature), it reaches the phase explosion threshold, and microbubbles begin to uniformly form inside the overheated liquid, ultimately leading to phase explosion. In this paper, based on the theory of laser ablation of metal targets, a numerical calculation model for nanosecond pulse laser ablation of aluminum alloy under auxiliary heating is established, and the vapor recoil pressure of nanosecond pulse laser ablation of aluminum alloy at different auxiliary heating temperatures is analyzed. The results show that at high temperatures of the target material under auxiliary heating, the absorption rate of the laser is higher, which allows lower energy laser to achieve the melting and vaporization process of the target material, thereby improving the energy utilization efficiency of nanosecond pulse laser and enhancing the laser-induced surface saturation vapor pressure and vapor recoil pressure.