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Influence of a local laser heat treatment on the bending properties of aluminium extrusion profiles
摘要： Driven by ecological and economical demands, lightweight design and in this context, the substitution of steel by aluminium has become a major trend in the automotive industry. However, design possibilities are limited by the low formability of aluminium alloys. One approach to overcome these limitations is the usage of tailor heat treated semi-finished products. By a local short-term heat treatment, distinct areas are softened, which can be used to improve the material flow into critical forming zones. Within this work, the influence of local short-term heat treatment on the formability of aluminium extrusion profiles is analysed by experimental bending tests. Aims are the enhancement of maximum reachable bending angles as well as the reduction of cross section deformations. Therefore, different heat treatment layouts are applied by laser irradiation. Finally, the bending results are evaluated and promising heat treatment strategies are derived.
关键词： heat treatment,bending,extrusion profiles,aluminium
更新于2025-09-12 10:27:22
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Microstructure development in Pulsed Laser Welding of Dual Phase Steel to Aluminium Alloy
摘要： Lap joining of aluminium 6061 and dual phase (DP 600) steel was carried out in pulse welding mode using a high power diode laser. The effect of laser parameters (laser power, scanning speed and pulse duration) on the microstructural evolution during conduction welding was studied. The large difference in thermal and physical properties of DP 600 and Al 6061 alloy results in the formation of brittle intermetallic phases along the interface of the weld zone. At a laser power of 4 kW, scanning speed of 5 mm/s and pulse duration of 10 ms the thickness of the intermetallic phase formed was found to be reduced i.e. in the range of 1- 7 μm. The porosity in the weld zone were mainly due to the entrapment of the zinc vapors during welding because of its low vaporization temperature compared to DP 600 and Al 6061 alloy. Microstructural characterization of the intermetallic phases was done using scanning electron microscopy, X-ray diffraction and the phase composition were characterized using energy dispersive spectroscopy. The micro-hardness testing was to evaluate the mechanical properties of the lap joint. A maximum hardness of 461 HV was observed along the weld- aluminium interface owing to the presence of hard and brittle Fe2Al5 and FeAl3 intermetallic phases.
关键词： Dual phase steel,Intermetallic phases,Pulsed laser welding,Aluminium alloys
更新于2025-09-12 10:27:22
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Fatigue Strength of Laser Beam Welded Steel-Aluminium Joints Considering Variable Amplitude Loading and Corrosive Environment
摘要： Hybrid material combinations of steel and aluminium are currently being joined by explosive welding in ship design, in order to reduce fuel consumption and increase transport weight. As an alternative to the elaborate and expensive explosive welding, a replacement for steel-aluminium adapters by means of laser beam welding in a lap joint configuration is being aimed at. Therefore, a laser beam welding process has been developed and optimised with regard to the different melting points and coefficients of thermal expansion of the materials as well as the formation of intermetallic phases due to the limited solubility of the elements. The characteristic of the weld seam, which is the result of a melt pool through the steel into the aluminium material, has a major impact on the quasi-static and cyclic strength of the joint. Especially the weld width and penetration depth have been identified as main influencing parameters. In the end, the developed laser beam welding process under spectroscopic control of the penetration depth is validated by fatigue investigations of lap joints and compact designed adapters. In addition to the fatigue strength under constant amplitude loading (CAL), the fatigue performance under variable amplitude loading (VAL) is particularly promising, even though the scatter increases from CAL to VAL and a linear damage accumulation is not applicable. A change in the fracture behaviour is explained by the intensity of the loading. Finally, the corrosion fatigue behaviour is shown by constant amplitude loading in a corrosive environment with a sodium chloride solution of 5 %, which causes a strength reduction from high cycle to long life fatigue.
关键词： steel-aluminium joint,ship building,corrosion fatigue,explosion welding,laser beam welding,lap joint,corrosive environment,ship design,constant amplitude loading,variable amplitude loading,compact adapter,fatigue assessment
更新于2025-09-12 10:27:22
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Surface Micro patterning of Aluminium Reinforced Composite for Aerospace Applications through High Energy Pulse Laser Peening
摘要： Aluminium (Al) Composites have universal engineering applications because of their higher strength to weight ratio, ductility, and formability. However, in diverse applications, mechanical properties such as hardness, corrosion, wear, and fatigue resistance are the prerequisite at closer surface regions. Such localised changes without impacting various surface treatment approaches can attempt the bulk phase. Laser shock peening is an advanced surface engineering technique, which has been successfully applied to improve the surface morphology and microstructure of the material. In this work, we are focusing on improving the surface properties of Al7075 reinforced with SiC and Zirconia through laser peening technique. The hardened layer was evaluated using surface integrity with optical microscopy, energy dispersive spectroscopy, scanning electron microscope (SEM) and analysis of microhardness. Process parameters and resulting microstructures of Aluminium composite are summarised, along with the impact of laser peening on surface properties. Research results indicated that laser peening shows a significant influence on the final condition of the surface layer of Aluminium composite.
关键词： Zirconia,Aluminium Metal Matrix Composites,SiC,SEM,Laser peening
更新于2025-09-12 10:27:22
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Self-plasticized, lumogallion-based fluorescent optical sensor for the determination of aluminium (III) with ultra-low detection limits
摘要： Aluminium-selective ion optical sensor based on covalently attached lumogallion methacrylate was synthesized and investigated in this study. Lumogallion based derivatives were copolymerized with various methacrylate monomers via a simple one step free radical polymerization to produce a "self-plasticized" copolymer. The mechanical properties of the copolymer were suitable for the fabrication of plasticizer-free optical membranes. We demonstrate that covalently attached lumogallion moieties provide adequate functionality to the optical film thus achieving a very simple, one component sensing membrane. Fluorescence experiments demonstrated excellent sensitivity towards aluminium (III) ions with the detection limits found at 4.8 x 10-12 M. Furthermore, proposed sensor displays high selectivity towards aluminium over a number of biologically relevant cations. Moreover, the synthesized copolymer was used for the fabrication of nanoparticles that exhibit strong fluorescence upon contact with aluminium (III) ions. It is anticipated that lumogallion-based copolymers may form the basis for the development of highly sensitive and robust aluminium selective sensors capable of in situ measurements.
关键词： self-plasticized copolymer,fluorescent optical sensor,lumogallion methacrylate,ultra-low detection limits,aluminium-selective
更新于2025-09-12 10:27:22
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[IEEE 2019 20th International Conference on Solid-State Sensors, Actuators and Microsystems & Eurosensors XXXIII (TRANSDUCERS & EUROSENSORS XXXIII) - Berlin, Germany (2019.6.23-2019.6.27)] 2019 20th International Conference on Solid-State Sensors, Actuators and Microsystems & Eurosensors XXXIII (TRANSDUCERS & EUROSENSORS XXXIII) - Application of MEMS Enabled Excitation and Detection Schemes to Photoacoustic Imaging
摘要： This paper shows, for the first time, a MEMS enabled photoacoustic system, using a custom MEMS Q-switched Nd:YAG laser for generation of photoacoustic (PA) waves and a custom-built MEMS thin-film aluminium nitride piezoelectric micromachined ultrasound transducers for PA wave detection.
关键词： Photoacoustic,Miniaturisation,PMUT,Aluminium Nitride,MEMS,Imaging,Q-switched Nd:YAG
更新于2025-09-11 14:15:04
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In situ investigation of precipitation in aluminium alloys via thermal diffusivity from laser flash analysis
摘要： In this work, a commercially available laser flash analysis (LFA) device is used for in situ precipitation monitoring in aluminium alloys by following thermal diffusivity for the first time. The LFA measurement methods and data processing are adapted to allow continuous heating experiments over a wide range of heating rates (0.001–1 K s-1). Methods for LFA temperature calibration and thermal lag correction are suggested. Results of continuous heating of Al Mn0.5Mg0.5 aluminium alloy from the as-cast state are compared to in situ differential scanning calorimetry (DSC) and ex situ transmission electron microscopy. It is shown comparing in situ LFA, and DSC substantially improves the interpretation of superimposed reactions, in particular, the precipitation and dissolution of Mn-containing dispersoids and Mg–Si-containing secondary particles.
关键词： DSC,In situ LFA,Thermal diffusivity,Aluminium alloys,Precipitation,LFA thermal lag correction
更新于2025-09-11 14:15:04
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Microstructure by design: An approach of grain refinement and isotropy improvement in multi-layer wire-based laser metal deposition
摘要： The additive production of metallic components with high-throughput is usually associated with high process temperatures and slow cooling rates. This typically results in strongly oriented columnar grain growth along the building direction of the structure having exceedingly large grain sizes. As a result, such structures show typically low strength and anisotropic mechanical behaviour in as-deposited condition. Consequently, post-processing is commonly performed to homogenize and eventually increase the mechanical properties of the deposited structures. In this regard, precise control of the applied process energy allows a modification of the local temperature distribution and cooling conditions during the additive manufacturing process, which strongly influence the resulting solidification microstructure. The aim of the present study is the development of an approach that allows to influence the solidification conditions in wire-based laser metal deposition of an Al-Mg alloy through specific adjustments of the laser irradiation. It was found that significantly different solidification microstructures in as-deposited condition can be achieved by adjusting the laser beam irradiance within a range resulting in conduction mode welding conditions while keeping the heat input constant. The application of high laser beam irradiances, close to the transition to keyhole mode welding, results in structures with a homogeneous large-grained solidification microstructure exhibiting a degree of anisotropy of around 12% between building direction and the direction of deposition. In contrast, the use of low laser beam irradiances close to the lower limit of stable melting, results in structures with a significantly refined microstructure. Consequently, an increase of yield strength of up to 16% and microhardness of up to 13%, as compared to structures processed with high laser beam irradiance, could be obtained. Moreover, the anisotropy of the as-deposited structure was reduced to a degree lower than 2%.
关键词： Direct Energy Deposition,Aluminium Alloy,Laser Metal Deposition,Additive Manufacturing,Laser Irradiance,Grain Refinement
更新于2025-09-11 14:15:04
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Nanostructure fabrication on the top of laser-made micropillars for enhancement of water repellence of aluminium alloy
摘要： Fabrication of superhydrophobic surfaces is a popular topic in research and industry due to many potential applications including self-cleaning, anti-icing or drag reduction. Laser micro and nanostructuring is an efficient method to replicate lotus leaves double-scale structures to achieve superhydrophobicity without chemical treatment. Immediately after laser processing, samples are hydrophilic and become hydrophobic in a few days, exposed to atmospheric conditions. This time was significantly reduced by vacuum processing to only 4 h. Two-step fabrication method of superhydrophobic surfaces have been developed using nanosecond laser system. In the first step, large scale micropillars are fabricated and covered by nano-scale protrusions in the following step using defocused laser beam. The nanostructure formation increased the apparent contact angle from 149° to 175°.
关键词： Nanostructures,Aluminium,Superhydrophobic,Fiber laser
更新于2025-09-11 14:15:04
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Effect of Overlapping of Peen Spots on Residual Stresses in Laser-Peened Aluminium Sheets
摘要： In this study, two di?erent laser peening systems were employed to investigate the e?ect of overlapping on the resulting residual stress ?elds. For each laser peening system, 2.0-mm-thick aluminium sheets were laser peened with di?erent amounts of overlapping. The residual stresses after laser peening were measured by incremental hole drilling. It was shown for both laser peening systems, that an increase in amount of overlapping induced higher magnitude compressive and deeper residual stress ?elds.
关键词： aluminium sheets,Laser peening,residual stresses,overlapping
更新于2025-09-11 14:15:04