Laserstrahlschweißen von Titanwerkstoffen unter Berücksichtigung des Einflusses des Sauerstoffes

Influence of the oxygen content in the shielding gas on microstructure and mechanical properties of laser welds of titanium and titanium alloys In the present work, a new tool concept for laser welding of titanium in high volume production has been presented and evaluated. Through the innovative application of a six‐layer metal web it is possible to calm the argon gas flow and avoid pernicious turbulences during welding. The integration of the mentioned metal web at the base of an open welding chamber allows the automated welding of highly reactive materials, such as titanium, under atmospheric pressure and inert shielding conditions. The higher density of argon relative to air offers the unique possibility to leave the chamber open on the top, so that a higher degree of flexibility than gas shielding devices for TIG welding, especially for industrial robots, is attained and can be successfully used for industrial mass production. Furthermore this device is important for welding three‐dimensional contours or to shield the regions of overlap (in overlapped joints) where shielding gas trailers are unsuccessful. By means of the presented gas shielding procedure and a modern laser welding process such as Nd:YAG laser welding, systematic investigations on the effect of oxygen on the microstructure as well as on the mechanical properties of reference bead‐on‐plate weldments could be performed for the first time. As a result of these welding trials it can be concluded that in order to avoid discolorations and hardness increase, lower restrictions to the purity of the shielding gas, in comparison to TIG welding condition, can be allowed. The maximum tolerable value of oxygen in the welding atmosphere was found to be approximately 1000 ppm for laser welding. On the contrary the maximum value for TIG welding is about 30 ppm. Further investigations on the microstructural and mechanical properties of the joints confirm that the optical quality assurance criteria for TIG welding due to the standards of aircraft construction transferable to Nd:YAG welding are.     

钛合金激光焊接技术研究进展及应用情况

介绍了激光焊接原理及特点,并根据钛合金激光焊接的三个典型问题,综合论述了为实现激光焊接钛合金所开展的基础研究工作,之后从焊接接头的组织性能、残余应力和变形以及应用范例来综述了钛合金激光焊接的研究进展和应用情况,为后续钛合金激光焊接的研究与应用提供参考和借鉴.     

Nd:YAG激光焊接对铝锂合金组织和织构的影响

采用Nd:YAG激光进行了5A90铝锂合金薄板的对焊实验,借助光学显微镜、扫描电镜及EDS能谱、背散射衍射技术测试了焊缝的显微组织、合金元素分布及焊缝中的微观织构,并与母材进行了比较。结果表明:Nd:YAG激光焊接使5A90铝锂合金的微观组织和微观织构发生了很大的变化。焊缝区呈现出大量的等轴枝晶组织,这是由于焊缝中存在较多的异质形核点和较高的成分过冷度。焊缝中织构呈随机分布的状态,激光焊接完全改变了母材面心立方金属的冷轧织构组织。     

Pulsed Nd-YAG Laser Welding of A SiC Particulate Reinforced Aluminium Alloy Composite

This paper examines the laser welding behaviour of a SiC particulate reinforced Al-alloy 2124 composite using a pulsed Nd-YAG laser. The influences of laser welding parameters of laser intensity, pulse duration and the beams focus position on the depth of weld penetration as well as the size of fusion zone were investigated. These investigations have led to an optimum welding condition proposed for pulsed laser welding of SiC particulate reinforced aluminium alloy composites with minimum defects.     

TA15钛合金电子束焊缝形貌及显微组织

对TA15钛合金厚板采用电子束焊接,研究了焊接速度为400mm／min和600mm／min的工艺条件下的焊缝形状、显微组织以及接头的显微硬度。结果表明：提高焊接速度,焊缝显微组织变得细小、均匀,热影响区收窄,接头上下部位显微硬度值更为相近,曲线也较陡直。     

Continuous Wave ND:YAG Laser Welding of Sand-Cast ZE41A-T5 Magnesium Alloys

A continuous wave 4 kW Nd:YAG laser system was used to weld 2-mm butt joints of sand-cast ZE41A-T5 magnesium alloys at a power of 2.5 kW, welding speed of 6.0 m/min, and defocusing distance from - 2 to + 3 mm for the material in the machined surface conditions. It was found that the adjustment of defocusing distance greatly influences the establishment of conduction or keyhole mode welding. Conduction welding is obtained at a power density of 4.0 × 10⁵ W/cm². Keyhole welding is reached at a threshold irradiance of 1.5 × 10⁶ W/cm². The fusion zone consists of refined equiaxed grains formed through cellular growth in the Zr-containing magnesium alloys. The partially melted zone is rather narrow, only a few grains wide. No grain growth or coarsening but softening is observed in the heat affected zone (HAZ). The weld defects observed include three main types: imperfect shape, cavities, and weld cracks. The mechanisms of their formations are discussed. In addition, the original cast quality was found to have a significant influence on the formation of defects such as underfill, surface depression, porosity, and burn-through during laser welding.     

Research and Progress in Laser Welding of Wrought Aluminum Alloys. I. Laser Welding Processes

With the wide application of Al alloys in automotive, aerospace and other industries, laser welding has become a critical joining technique for aluminum alloys. In this review, the research and progress in laser welding of wrought Al alloys have been critically discussed from different perspectives. The primary objective of this review is to understand the influence of welding processes on joint quality and to build up the science base of laser welding for the reliable production of Al alloy joints. Two main types of industrial lasers, carbon dioxide (CO₂) and neodymium-doped yttrium aluminum garnet (Nd:YAG), are currently applied but special attention is paid to Nd:YAG laser welding of 5000 and 6000 series alloys in the keyhole (deep penetration) mode. In this part of the review, the main laser welding processing parameters including the laser-, process-, and material-related variables and their effects on weld quality are examined. In part II of this article in this journal, the metallurgical microstructures and main defects encountered in laser welding of Al alloys such as porosity, cracking, oxide inclusions, and loss of alloying elements are discussed from the point of view of mechanism of their formation, main influencing factors, and remedy measures. In part II, the main mechanical properties such as hardness, tensile, and fatigue strength and formability are also discussed.     

Fügen von Magnesium und Magnesiumlegierungen

Welding of Magnesium and Magnesium alloys Magnesium is mainly connected by screws. In this paper the results of experiments with different welding processes will be presented. The following methods have been applied: TIG, MIG, Nd: YAG‐Laser and CO₂‐Laser welding, electron beam welding and High Power Diode Laser welding.     

用KrF准分子脉冲激光在低基板温度下制备AlN薄膜的研究

用KrF准分子脉冲激光在 2 0 0℃的Si(111)基板上通过改变制备条件 ,采用沉积后直接保温处理的方式制备出了具有不同择优取向的AlN薄膜 ,并得出了较高的处理温度和过长的时间不利于AlN相的形成的结论。     

单晶硅材料的1064nm Nd:YAG脉冲激光损伤特性研究

作为微电子和光电子系统中普遍使用的一种结构材料,单晶硅一直是人们研究的焦点.长期以来,人们对其电学性质进行了非常深入细致的研究,却疏于对其抗击强激光辐照特性的研究.随着激光通讯和光电对抗技术的发展,对光学材料的激光破坏特性和加固技术进行研究的需求也显得越来越迫切.本文主要对单晶硅的抗激光损伤特性进行研究,研究了单晶硅材料在1064nm Nd:YAG激光自由脉冲输出模式和单脉冲输出模式作用下的损伤特性,通过对两种激光作用下单晶硅损伤形貌的分析,在热效应与热力耦合模型的基础上,对单晶硅的激光损伤机制进行了探索.     

Thermische Nachbehandlung der laserstrahlgeschweißten Al‐Legierungen AlSi1MgMn und AlCu4Mg1

Post heat treatment of the laser beam welded aluminium alloys AlSi1MgMn and AlCu4Mg1 Laser beam welded age hardenable aluminium alloys often exhibit a loss in strength in the fusion and the heat affected zones, compared to the uninfluenced base material. A material‐compatible combination among a base material, a welding filler material, as well as welding parameters and a suitable post heat treatment of the welded joint allows to improve the weld seam properties. The base material AlSi1MgMn (6082) was welded in the aging condition T4 using AlSi12 and AlSi7Mg ‐ filler materials and the welded joint was completely aged at different temperatures and times, in order to adjust an almost constant hardness profile over the base material, heat affected zone and fusion zone. The base material AlCu4Mg1 (2024) was welded in the aging condition T351 using a AlCu6Mn ‐ filler material and the welded joint was naturally aged. The aging behaviour, the residual stress, the static and dynamic properties of welded joints were examined. The properties can be clearly improved by the post heat treatment.     

Dot Matrix Hardening of Steels Using a Fiber Optic Coupled Pulsed Nd:YAG Laser

This paper describes a novel process called “Dot Matrix Hardening” as applied to Ol, D2 and AISI 4340 steels. This process uses a pulsed laser (particularly an Nd:YAG laser) to create a uniform distribution of transformation-hardened spots to cover only a certain percentage of the desired surface. Due to significantly reduced energy input, wear resistance can be imparted to thin and intricate parts without distortion. In addition, with the use of a coupled fiber optic beam delivery system, this process provides greater flexibility compared to conventional CO₂ laser hardening for a number of applications. The use of an Nd:YAG laser also eliminates the need of absorptive coating required for hardening with a CO₂ laser. With optimized processing parameters, a relatively uniform hardened layer is obtained within the hardened spot, with a thickness of about 60 um and hardness values around 800 HV₁₀₀. The sliding wear test results show that the wear resistance of Ol samples with only 20-40% area coverage of laser-hardened spots is similar to the 100% covered laser dot hardened sample as well as the furnace hardened (Re 60) sample.     

Q-switch Nd:YAG laser welding of AISI 304 stainless steel foils

Conventional fusion welding of stainless steel foils (<100 μm thickness) used in computer disk, precision machinery and medical device applications suffer from excessive distortion, formation of discontinuities (pore, void and hot crack), uncontrolled melting (melt-drop through) and poor aesthetics. In this work, a 15 ns pulsed, 400 mJ Nd:YAG laser beam was utilized to overcome these barriers in seam welding of 60 μm thin foil of AISI 304 stainless steel. Transmission electron microscopy was used to characterize the microstructures while hardness and tensile-shear tests were used to evaluate the strengths. Surface roughness was measured using a DekTak profilometer while porosity content was estimated using the light microscope. Results were compared against the data obtained from resistance seam welding. Laser welding, compared to resistance seam welding, required nearly three times less heat input and produced welds having 50% narrower seam, 15% less porosity, 25% stronger and improved surface aesthetics. In addition, there was no evidence of δ-ferrite in laser welds, supporting the absence of hot cracking unlike resistance welding.     

A Comparison of Laser Cladding Ni-based Coating on an Aluminium Alloy with CO_2 Laser and Nd: YAG Laser

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Dissimilar welding of carbon steel to 5754 aluminum alloy by Nd:YAG pulsed laser

Laser welding of low carbon steel to 5754 aluminum alloy was studied in keyhole welding mode in steel-on-aluminum overlap configuration. In order to decrease formation of intermetallic components during laser welding, effect of laser power, pulse duration and overlapping factor was investigated. Tensile test was performed to identify the effect of each parameter on the weld. The phase composition was characterized by energy dispersive spectrometry and Vickers microhardness test and microstructure by optical and scanning electronic microscopes. Results obtained show that increasing peak power (in constant pulse energy), pulse duration (in constant peak power) and overlapping factor (in constant pulse energy and peak power) will increase percentage of intermetallic components (PIC). On the other hand, decreasing the mentioned parameters will cause destructive effects such as inadequate penetration depth, spattering and cavity formation. Improvement in the tensile strength was attributed to low values of intermetallic components in weld metal. Finally, an optimized peak power, pulse duration and overlapping factor were reported.     

Research and Progress in Laser Welding of Wrought Aluminum Alloys. II. Metallurgical Microstructures, Defects, and Mechanical Properties

With the wide application of aluminum alloys in automotive, aerospace, and other industries, laser welding has become a critical joining technique for aluminum alloys. In this review, the research and progress in laser welding of wrought aluminum alloys are critically discussed from different perspectives. The primary objective of the review is to understand the influence of welding processes on joint quality and to build up the science base of laser welding for the reliable production of aluminum alloy joints. Two main types of industrial lasers, carbon dioxide (CO₂), and neodymium-doped yttrium aluminum garnet (Nd:YAG), are currently applied but special attention is paid to Nd:YAG laser welding of 5000 and 6000 series alloys in the keyhole (deep penetration) mode. In the preceding article of this review (part I), the laser welding processing parameters, including the laser-, process-, and material-related variables and their effects on welding quality, have been examined. In this part of the review, the metallurgical microstructures and main defects encountered in laser welding of aluminum alloys such as porosity, cracking, oxide inclusions, and loss of alloying elements are discussed from the point of view of mechanism of their formation, main influencing factors, and remedy measures. The main mechanical properties such as hardness, tensile and fatigue strength, and formability are also evaluated.     

TiNi形状记忆合金/不锈钢异种材料激光焊研究

采用纯镍中间夹层和激光焊技术,连接TiNi形状记忆合金丝和不锈钢丝异种材料。对比分析了加镍夹层与未加镍夹层的激光焊接头的组织和性能。结果表明,与未加镍夹层的接头相比,加镍夹层的接头组织和性能得到明显改善,接头组织中γ-Fe相含量增加,TiFe2,TiCr2等金属间化合物相含量减少,焊缝区硬度明显降低,接头抗拉强度提高。未加镍夹层的接头的抗拉强度仅为187MPa,断口呈现典型的脆性断裂特征。加镍夹层后,接头抗拉强度提高至372MPa,断口具有脆-韧混合型断裂特征。