在亚音速气流作用下连续激光辐照铝合金的穿孔效应

Perforation effect of CW laser irradiation on aluminum alloy under subsonic flow

不同气流速度作用下激光辐照靶材的穿孔效应不同。实验研究了亚音速气流(0~0.7 Ma)环境下,1070 nm连续激光辐照7075铝合金的穿孔效应。对铝合金中心点温度历史、穿孔时间、穿孔孔径以及表面形貌变化进行了分析,结果表明:在相同气流速度下,随着入射激光功率密度的增加,铝合金表面温升速度加快且最终熔融层所达到的平衡温度增大;铝合金的穿孔时间呈指数减小;孔径增大速率呈指数减小。在相同激光功率密度下,随着气流速度的增加,铝合金穿孔时间总体呈先增大后减小至平稳之后再增大的趋势;熔融物移除速度和气流的冷却作用这两方面共同导致在0.1 Ma附近出现最长穿孔时间,在0.3 Ma附近出现最短穿孔时间,0.6 Ma的穿孔时间与0 Ma的穿孔时间大致相等在5.5 s左右;随着气流速度增大冷却效应增强,在0.7 Ma之后铝合金并未出现穿孔。对流冷却导致熔融物快速冷凝,被移除的熔融物集中在气流的下游区域。

The perforation effect of laser irradiated target is different under different airflow velocity.The perforation effect of 7075 aluminum alloy irradiated by 1070 nm CW laser under subsonic airflow(0-0.7 Ma)was experimentally studied.The temperature history,perforation time,perforation aperture and surface morphology of the center point of the aluminum alloy were analyzed.The results show that under the same airflow velocity,with the increase of the incident laser power density,the temperature rise rate of the aluminum alloy surface increases and the equilibrium temperature of the final melting layer increases.The perforation time of aluminum alloy decreases exponentially;the increase rate of pore size decreases exponentially.At the same laser power density,with the increase of airflow velocity,the perforation time of aluminum alloy increases first and then decreases to a stable and then increases.Both the removal rate of melt and the cooling effect of airflow lead to the longest perforation time near 0.1 Ma and the shortest perforation time near 0.3 Ma.The perforation time of 0.6 Ma is roughly equal to that of 0 Ma about 5.5 s.With the increase of airflow velocity,the cooling effect increases,and there is no perforation in the aluminum alloy after 0.7 Ma.Convection cooling leads to rapid condensation of the melt,and the removed melt concentrates in the downstream area of the airflow。