【作者】 王新林；

【导师】 郑启光； 陆培祥；

【作者基本信息】 华中科技大学 ， 物理电子学， 2007， 博士

【摘要】 采用飞秒激光微细加工系统,开展了飞秒激光烧蚀与微细加工新型金属材料-非晶合金特性的实验研究;结合理论模拟,开展了飞秒激光微细加工不锈钢、镍等金属材料的工艺优化与微型零件制备及应用的实验研究。全文的主要研究内容、结论与创新性如下:(1)总结分析了飞秒激光烧蚀金属材料的一般物理过程与物理机制,采用结合双温模型的分子动力学模拟方法,初步数值模拟了飞秒激光烧蚀单质金属镍的物理过程,揭示了在高低不同的两种脉冲能量密度下存在两种不同的烧蚀机制。并数值模拟了实验室参数条件下飞秒激光烧蚀金属镍的物理过程及特征。(2)介绍了飞秒激光微细加工系统的组成与工作原理,特别是光路装置的设计搭建。测试分析了加工系统中光束传输变换过程中脉冲宽度、光斑大小与光强空间分布等飞秒激光的主要参数。(3)首次系统地研究了飞秒激光烧蚀Zr基非晶合金的特性及微细加工工艺。采用光学显微镜、扫描电镜(SEM)与其附件电子能谱仪(EDX)、透射电镜(TEM)与其附件电子衍射仪(EDD)等方法与技术,确定了飞秒激光烧蚀Zr基非晶合金的单脉冲烧蚀阈值,分析了飞秒激光烧蚀非晶合金的表面形貌、表面氧化现象与无晶化微细加工条件。结果显示:单脉冲烧蚀时的典型表面形貌为周围隆起的圆形弹坑;多脉冲烧蚀时,在烧蚀表面出现周期性波纹结构与积雪状形貌,在高的能量密度下会发生表面氧化,氧化层的厚度在纳米量级;在选择合适参数的条件下,首次实现了微米级的飞秒激光无晶化微细打孔与切割。表明飞秒激光微细加工是一种极有前途的非晶合金无晶化微细加工手段。(4)开展了不锈钢与镍的飞秒激光微细加工工艺参数优化及微零件制备与应用的实验研究。研究了飞秒激光微细切割不锈钢与金属镍的工艺与参数优化,采用优化后的工艺参数加工出了高质量的微型悬臂梁;首次将飞秒激光加工的不锈钢与镍微型悬臂梁在NaCl溶液中进行了腐蚀疲劳实验,得出了对MEMS金属零件的可靠性设计与应用有重要指导意义的结果;以研究飞秒激光直接加工技术的柔性为目的,开展了飞秒激光在不锈钢箔片上直接微细加工多种微型图案、结构与零件的研究,并制备出高质量的用于脉冲激光沉积(PLD)实验的电极掩模板。更多还原

【Abstract】 Using the femtosecond (fs) laser micromachining system, the experimental investigations of fs laser ablating and micromachining the new type of metallic material—amorphous alloy were performed. Combined with the theoretical simulation, the parameter optimization of fs laser micromachining stainless steel and nickel was conducted for fabrication and application of metallic microcomponents. The main contents, research conclusions and contributions to innovation are summarized as following:(1) The general physical processes and mechanisms of fs laser ablating metallic materials in the previous works were systematically analyzed and summarized. With the method of molecular dynamic simulation combined with the two-temperature model, the physical process of fs laser ablating nickels was theoretically simulated. The results show two regimes of fs laser ablation nickel under high and low fluences.(2) The architecture and working principle of the fs laser micromachining system, especially, the optics propagation and processing device, were described detailedly. Checking and analyzing of the fs laser parameters and their changes, such as pulse duration, spot size and spatial distribution of intensity were performed while the laser beam propagated through the system.(3) Femtosecond laser ablating and micromachining of a Zr-based amorphous alloy in air were investigated in detail for the first time. Laser-induced ablation and related effects were examined by means of scanning electron microscopy (SEM),energy dispersive X-ray analysis (EDX), transmission electron microscopy (TEM) and electron diffraction diagram (EDD). The ablation threshold of fs laser ablating the Zr-based amorphous alloy was determined. The results show that the surface morphology of single-pulse ablation region seems like a circular crater with edge upheaved; in the multi-pulse ablation region surface, periodic ripples and firn-like morphology appeared; slight oxidation occurred at high laser fluences, and the thickness of the oxidation layer is determined to be nano-scale. With selected parameters, micron-size scale holes and trenches machined without crystallization around the ablated region were achieved for the first time. The results show that femtosecond laser ablation with selected parameters is a promising method for non-crystalline micromachining of amorphous alloys. (4) Femtosecond laser direct fabrication of stainlesssteel and Ni microcantilever was investigated, and the laser processing parameters were optimized. The metallic microcantilevers of good quality with structure and dimensions according commendably with that of the designed cantilever were obtained. Using the fs laser fabricated metallic microcantilever, the cyclic fatigue test under corrosion was investigated for the first time. The testing results are very important for the design and application of metallic MEMS devices. Femtosecond laser direct fabricating various stainless steel micro-patterns, microstructures and components were also conducted to investigate the flexibility of fs laser micromachining technology. A microhole electrode mask was successfully fabricated for pulse laser deposition (PLD) experiments.更多还原