Diamond-reinforced FeCoCrNiAl0.5Ti0.5Si0.2-carbonized high-entropy alloy coating was prepared on the surface of TC4 by laser cladding. The effects of diamond contents (4, 8, 12 wt%) on the macroscopic morphology, microstructure, microhardness, and wear resistance of coating were studied. The results showed that all the coatings had smooth surface and good bonding with the substrate. The dilution rate of coating decreased with the addition of diamond. Coating was mainly composed of BCC1 and BCC2 solid solution. TiC and Cr23C6 phases appeared in the coating after adding diamond. The maximum microhardness of S1 coating was 559.34 HV0.2, 1.6 times that of the TC4, and that of S4 coating was 1038.42, HV0.2, 3 times that of the TC4. With the addition of diamond, the main wear form of coating changed from adhesive wear to abrasive wear. Compared with TC4, the wear loss of S4 coating decreased by 64.4%.

激光冲击强化是一种利用激光束对金属材料表面改性的表面强化技术,能够改善材料表层微观组织,产生加工硬化和一定深度的残余压应力,有效提高材料疲劳性能、延长材料服役寿命.介绍了激光冲击强化的技术原理,综述了激光冲击强化技术的工艺参数、数值模拟和主要应用研究,并就该技术后续研究与发展进行了展望.

The inhomogeneous microstructure and fatigue crack propagation of 30 mm thick-section high strength steel welded joint by double-sided hybrid fiber laser-arc welding were investigated in detail. The results indicated that the average effective grain size of the laser zone was only 1/2 of that of the arc zone, due to the faster cooling rate of the laser resource. The base metal consisted of massive polygonal ferrites and small granular carbides, while fine grained region, the coarse grained region and weld metal were all composed of martensite with a high dislocation density. Compared with the arc zone, the percentage of grain boundaries with high misorientation angle increased 24% for the laser zone, as the average grain size of the laser zone was smaller than that of the arc zone. The results also revealed that the fatigue crack propagation resistance of the welded joint was higher than that of the base metal. Meanwhile, a significant increase in the fatigue crack propagation resistance of the laser zone occurred, as compared with the arc zone, due to the refined grains and the high proportion of the grain boundaries with high misorientation angle (>15 degrees) in the laser zone.

在WC粒径0.7～0.8 μm、质量分数91.5％～92.0％的Co-WC二元硬质合金上进行了恒定单脉冲能量下,不同填充间距和加工次数的皮秒脉冲激光加工工艺试验研究,发现在小于光斑宽度的填充间隔尺寸范围内,填充间隔增大,加工面呈现表面粗糙度降低的光整加工效果;填充间距减小,激光对材料的蚀除效果增加;加工次数越多,材料去除深度越大;加工次数持续增加,材料表面钝化失活,激光的蚀除作用减弱;通过对激光加工区域的残余应力检测,发现皮秒激光加工对硬质合金表面残余应力影响不明显;对硬质合金钻头副切削刃口进行脉冲激光刃口修磨,去除了砂轮修磨残留的微观缺口,获得了更好的刃口质量和前刀面表面质量.

The temperature varying principal of the molten pool is crucial to coatings' cross-section sizes during laser cladding process, which can influence the performance of the coatings. In this study, a modified threedimensional (3D) transient finite element model was presented to simulate the temperature evolution and clad geometry of the molten pool of TiAlSi coatings. The difference of thermal properties in TiAlSi powders and TiAlSi alloys were distinguished to improve the precision of simulation results through theoretical calculation. The Gaussian body heat source model was established. A temperature selection judgment mechanism was utilized to compare the average temperature of the element and the melting point of the material to distinguish powder and alloy elements. An exponential distribution of energy attenuation along penetration direction was employed to simulate the laser beam deflected by the powder particles and the void among the particles to correct Gaussian heat source. The effect of different laser power and scan speeds on the cladding layer morphologies were investigated. The track depth and width calculated by simulation were analyzed by polynomial fitting curves. The results showed that the track depth and width were directly proportional to laser power, whereas inversely to scanning speed. Geometric dimensions of cladding layers at arbitrary laser power (600-1800 W) and scan speed (0.005-0.025 m/s) can be computed by polynomial fitting equation. Track depth was more impressed by scanning speed. The track width and longitudinal size of cross-section geometry from the simulation results and experiment measurement were matched to validate the presented model. The modified 3D transient finite element model is able to describe the geometry of single-track laser cladding.

表面镀金属薄膜的复合材料具有耐热、抗辐射和低膨胀率等特点,是一种应用于航空航天、信息传导等领域中电磁波传输控制的高效透波材料.以复合材料基底不损伤为前提,实现对特定金属覆膜结构的精准、低损剥离刻蚀是其发挥功能的必要条件.本文针对铝覆膜石英纤维复材结构的剥离刻蚀需求,探索研究了超快飞秒激光扫描次数、光斑搭接、能量密度等关键参数对刻蚀结果的影响与表现.研究发现采用脉冲频率100 kHz、波长1 030 nm、脉宽480 fs的超快激光刻蚀时,参数组合为:能量密度3.80 J/cm2,光斑搭接率60％,光束扫描次数为3次情况下,可以实现基材纤维基本无损伤的铝膜刻蚀与剥离.上述研究结果可用于铝覆膜石英纤维复材结构件的低损激光刻蚀,也可为其他类似结构的透波材料高质量超快激光加工提供研究思路和方法.

The silicon material is very sensitive to the change of the laser, and a small change in energy will cause a relatively large change in the morphology of the mark. Therefore, it is a great challenge to produce uniform and high-quality laser marks on silicon wafers. A new Master Oscillator Power-Amplifier (MOPA) fiber laser with independently adjustable pulse width and frequency have a wide adjustable parameter window. In this paper, a new type of MOPA fiber laser is used to study the marking process on silicon wafers. By changing average power (defined by the active current set point), pulse repetition frequency (PRF) and pulse duration of the laser (i.e., the number of pulses), dot matrix marking on the wafer, using the Keyence VHX-6000 optical microscope to determine the cleanliness and surface topography of the wafer surface to evaluate. Studies have shown that the influence of the output instability of the fiber laser on the marking quality can be reduced by increasing the number of pulses under the condition of stable and low power. At the same time, the resolution of the single pulse energy of the laser is improved by changing the laser PRF, and then the control precision of the energy is improved, so as to realize the high-quality silicon wafer laser marking process with uniform and stable marking morphology.

Pulsed lasers were used extensively in material processing including cutting, drilling and marking. The temporal shape and duration of the pulse were important in optimizing the material processing quality. The flexible parameters of MOPA pulsed fiber laser can offer a broad range of material response characteristics. In this report, a MOPA pulsed fiber laser was configured with pulse duration from 2 to 500 ns and PRF that ranged from single shot to 4000kHz.Pulse energy up to 1mJ to investigate independently the contributions of each of these parameters on the marking process of Si wafer. Various experiments were presented to require the high quality marking on Si wafer. Topography evolution pictures of dot were taken and the depths were measured. Experimental results showed that single pulse energy had a significant influence on the threshold of the visible mark. Pulse numbers had more impact on the dot topography. Pulse energy and pulse duration had more influence on the mark depth. In order to control finely the mark depth, single pulse energy and pulse numbers should be optimized.

Surface texturing experiments of 301 stainless steel sheets by using picosecond laser were carried out.The effects of different laser power (7.4,24.3,49.3 W),processing speed (1 000,1 500,2 000,2 500 mm/s) and repetitions (1,5,10,15,20,25 times) on surface groove width,depth and morphology were investigated.The results show that with the increase of laser power and decrease of processing speed,the surface groove width,depth and the heat affected zone increase,some tiny melting particles appear locally on the edge of grooves.With the increase of repetitions,the surface groove width increases obviously,but the surface groove depth does not change obviously.When the repetitions exceed about 20 times,the surface groove depth increases obviously.The effects of different spacing (10 μm,15 μm,20 μm,40 μm,100 μm) of groove microstructure on the properties of friction were investigated simultaneously.The results show that the friction coefficients of the area without texture is 0.8～0.9.The friction coefficients of the texture area are generally smaller than the area without texture.Friction coefficient decreases with the decrease of the groove spacing.The friction coefficients of the 10 μm spacing groove texture area drop to about 0.1.Friction coefficients of texture area are stabilized much faster than friction coefficient of no texture area.

激光直接零部件标识(Laser Direct Part Marking)技术是一种在工业环境中证实可行,可实现高度自动化且绿色环保的标识技术,已经成为工业产品追溯中产品标识的首选手段.本文基于控制灵活、激光参数调节范围更大的MOPA(MOPA,主控振荡器的功率放大器)激光标识设备,按照ISO/IEC TR 29158条码技术标准,开展激光加工参数(如激光峰值功率、激光单脉冲能量、激光功率、填充间隔、扫描速度等)对激光直接标识(Direct Marking,DM)码质量(如条码等级、对比度、打印伸缩等)影响的研究.通过优化激光加工参数,实现了在AL2024材料表面标识高质量DM码的激光标识工艺.

碳纤维复合材料(CFRP)是由碳纤维和基体组成的二相或多相结构,具有非均质和各向异性,且碳纤维的硬度很高,采用传统的机械加工方式易出现如刀具磨损、复合材料分层、纤维破碎及加工后性能变差等问题.使用激光加工可以克服其技术方面所面临的各种困难,但由于CFRP中碳纤维增强体在热膨胀系数、气化温度等热力学性能方面与基体存在相当大差异,激光加工过程中易出现热影响区、纤维拔出、复合材料分层、纤维末端膨胀等热损伤缺陷,严重影响CFRP的静态强度,导致激光加工CFRP面临巨大挑战.综述了国内外降低激光加工碳纤维复合材料的研究现状,通过采用短脉冲、短波长、重复频率高的激光光源,以及提高加工速度、改进加工路径、一定压力的吹气等多种方法降低激光与材料的作用时间,从而减少热效应.

The picosecond laser is used to form six different regular morphology microstructures on the surface of the stainless steel. These microstructures have micro-scale corrugated protrusions, and the surface of the protrusions is distributed with small micro-pits of nanometer scale. The elements composition of the processing area is basically the same as that of the substrate, and the content is also close. The content of C element increases and the content of Fe element decreases. The results show that the friction coefficient of the original surface is between 0.8 and 0.9, and the friction coefficient of the textured surface is reduced to between 0.1 and 0.2. The friction coefficient shows a stable change after climbing first, but the time when the textured surface reaches the steady state relative to the original surface is shorter. The wear scars of textured surface are wider than that of the original surface. It has better wear resistance when the rubbing direction is perpendicular to the texture. The wetting angle of the original surface is <90°, and the surface is hydrophilic. The wetting angle of the textured surfaces are >90°, most of which are 110°~120°, and the surfaces are hydrophobicity. The surface friction coefficient is inversely related to the surface wetting angle.

采用皮秒激光在不锈钢表面加工形成了6种不同规则形态的微结构,这些微结构微观形貌呈现微米级类波纹状突起,突起表面分布有一个个纳米级的小微坑.加工区域元素的组成成分基本和基底一样,含量也接近,只有C元素含量有所增加,Fe元素含量有所降低.织构区域的摩擦系数普遍都比无织构区域小,无织构的不锈钢薄板摩擦系数在0.8～0.9之间,而织构过的表面摩擦系数明显降低,在0.1～0.2之间.摩擦系数均呈现出先爬升后稳定的变化,但织构表面相对未织构表面摩擦系数达到稳定状态的时间较短.织构表面摩擦系数在4 000～7 500 s时显著升高,表面微结构的减磨作用贡献结束.织构表面磨斑均比原始表面的磨斑宽,当摩擦方向垂直于织构表面,具有更好的减磨作用.

精密加工机床工作台的平面度是影响机床加工质量的重要因素,是机床设计加工的关键指标,其准确测量对指标校核有重要作用.从机床工作台平面度的测量需求出发,提出了采用激光准直仪测量数据,基于最小二乘法建立平面度的数学模型,采用Matlab进行平面度的评定,并且利用Matlab的图形用户界面(GUI)环境设计了平面度计算软件,提供了一套完整的平面度测量方法,并且对动态变化条件下的平面度进行了测量分析.结果表明,机床的工作台平面度在长期的工作中保持较高的精度,保证加工需求.

采用连续光纤激光器在不同焊接速度下(分别是0.9、1.2、1.5 m/min)对1 mm厚的304不锈钢薄板进行直角拼焊,研究了焊接速度对焊缝形貌的影响.结果表明,焊接速度影响焊缝的表面形貌和平整度.当焊接速度为0.9 m/min时,焊缝形貌较为稳定,也更平坦,高低起伏最小,表面未见明显的夹杂物;随着焊接速度增大,焊缝表面起伏变大,可见较多尺寸较大的块状夹杂物.同时,光束沿与水平钢板呈45°角方向照射的焊接方式,能得到较圆滑、有较好弧度的焊缝.通过工艺试验,为激光焊接在不锈钢薄板外观件实际焊接应用提供工艺方法实验指导.

金属材料的激光焊接已经得到了较广泛的应用,而激光焊接塑料的研究正刚刚起步.随着塑料激光焊接设备的逐步商品化,塑料激光焊接的应用必将越来越广泛.设计并确定了激光焊接的实验方案,通过工艺试验及数值模拟分析,优化工艺参数,提高焊接强度和焊接精度,为塑料激光焊接在生产实际中的应用提供工艺方法实验指导.

基于Pangolin激光演示软件,介绍了若干能将不同格式的图文影像文件在激光演示系统中转换的插件和专用软件,并开展各种素材文件格式转换及优化技术研究,从而为激光表演在不同场合的应用提供必要的技术支撑,提高了激光演示的表现能力,在实际应用中达到了更好的艺术效果.

随着激光器性能的改善和新型激光器的发展,激光表演系统的安全性、易使用性和易操作性得到了大幅的提高,在舞台灯光布置、娱乐场所和户外显示方面得到广泛应用.概述了新型激光表演系统的组成及设计要求,主要由激光器、振镜、色彩控制器和控制软件几部分组成.详细分析了当前激光系统、激光器、振镜以及控制软件的技术状况及其国内外先进产品性能,并提出了国内激光表演系统的发展趋势.

LED因其节能、环保、寿命长等特点,已渐渐被广泛应用于照明产业.为了兼顾LED照明的光效率与光束整形均匀化问题,人们开发了光扩散膜技术.本文概述了LED照明产业国内外市场最新的发展动态,光扩散膜的原理与制作工艺,着重研究了光扩散膜的光匀化机理、不同微结构膜的光扩散效果和透过效率,分析了其在LED照明产业中的技术状况及应用趋势.指出,解决和掌握光扩散膜制作和产业化应用的核心技术,是推动我国LED照明市场快速发展的关键.