中文摘要：

为探究超快脉冲激光对难加工材料的烧蚀特性与损伤机制,利用皮秒脉冲激光研究钛合金的烧蚀阈值、烧蚀形貌和作用机理.依据烧蚀面积和激光能量密度的线性关系,确定了钛合金的烧蚀阈值,通过显微镜观察分析了不同激光参数下钛合金的表面烧蚀形貌,采用雪崩电离与多光子电离详细解释了超快脉冲激光对钛合金的作用机理,并从烧蚀形貌和阈值角度划分了烧蚀区域.结果表明：钛合金的烧蚀阈值约为0.109 J/cm2;在1 064 nm波长下的烧蚀质量要优于532 nm波长下的质量,而低重复频率能获得高质量的微结构,烧蚀中央区域材料去除更为均匀,且烧蚀弹坑形状规则,表面平滑;随着脉冲数和能量的增加,光子能量累积增多,烧蚀尺度和形貌特征愈加明显,烧蚀边界愈加清晰,说明脉冲数和光子能量累积是表面微结构诱导的关键要素之一;烧蚀区域可划分为改性区、过渡区、再沉积区和烧蚀区,在烧蚀区以多光子电离为主,在改性区、过渡区和再沉积区以雪崩电离为主.该结果可为超快脉冲激光微结构精密加工提供参考.

英文摘要：

To reveal ablation characteristics and damage mechanism of difficult-to-machine material processed by ultra-fast pulse laser, the ablation threshold, ablation morphology and interaction mechanism of titanium alloy are investigated by picosecond pulse laser. Focusing on the linear dependence of laser energy density on the ablation area, the threshold fluence of ultra- fast pulse laser-induced ablation in titanium alloy is determined. The ablation morphologies of titanium alloy surface under the different laser parameters are observationally analyzed. The interaction mechanism of titanium alloy processed by ultra-fast pulse laser is explained in detail with the theories of avalanche ionization and multiphoton ionization, and the different ablation zones are distinguished according to the ablation morphology and threshold fluence. The results show that the ablation threshold of titanium alloy reaches 0. 109 J/cm2 ; the ablation quality of titanium alloy processed by a picosecond pulse laser of 1 064 nm wavelength gets better than that by 532 nm wavelength, and low repetition rate favors high-quality microstructure; the ablative central area has smooth surface. more uniform material removal, and the ablation crater has regular shape and With increasing pulse number and laser energy, the accumulation of photon energy increases, ablation dimension and morphological characteristics become more obvious, and the ablation boundary becomes more distinct. It indicates that pulse number and accumulation of photon energy are respectively one of the key factors for inducing surface microstructure. The observed ablation zone can be divided into modified region, transition region, redeposition region and ablation region. Multiphoton ionization dominates in the ablation region, while avalanche ionization dominates in the modified, transition and redeposition regions.