为了获得纳秒激光脉宽对铝材的损伤特性, 给纳秒激光金属加工的脉宽选择提供依据, 采用面积推算法, 利用光学显微镜、扫描电镜、表面轮廓仪等仪器, 测试了37种脉宽纳秒激光(脉宽10ns～520ns, 波长1064nm)对铝材的损伤阈值。研究了脉宽不变时激光脉冲数目对铝板的损伤规律, 揭示了不同脉宽纳秒激光对铝板打孔的作用机理。结果表明, 单脉冲损伤阈值与纳秒激光脉宽的平方根成线性关系。当脉冲个数增加时, 材料的损蚀阈值呈现下降趋势; 铝板打孔时, 纳秒激光的脉宽越窄, 对铝的损伤阈值越低; 打孔过程中蒸发过程占主导, 孔内壁烧蚀熔融物越少, 孔圆度越好, 孔口喷溅物越少, 打孔质量越高。该结果可为纳秒激光金属加工的脉宽选择提供参考。

In order to get the damage features of nanosecond laser pulse width to aluminium and provided the basis for choosing proper pulse width in the processing of metals by nanosecond laser, by using the area calculation method and instruments (optical microscope, scanning electron microscope and surface profiler), the damage thresholds of 37 kinds of nanosecond laser (pulse width of 10ns~520ns, wavelength of 1064nm) on aluminium were obtained. The effects of laser pulse number on damage thresholds of aluminium were analyzed with constant pulse width. The function mechanism of nanosecond laser pulse width on the quality of drilling holes in aluminium was also revealed. The results show that the damage threshold of single pulse is linearly related to the square root of laser pulse width of nanosecond laser. The damage threshold of aluminium decreases with the increase of the number of pulse width. The narrower the pulse width of nanosecond laser is, the higher the damage threshold to aluminium is. Evaporation process occupies the leading position during the drilling process. Furthermore, the less the melted thing on the inner wall of hole is, the better the circular degree of hole will be. The less the spraying materials in the orifice is, the higher the quality of drilling will be. The results provide the guide for choosing proper pulse width in the processing of metals with nanosecond laser.