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Pore Formation during Laser Welding in Different Spatial Positions
摘要： The process of formation of pores, cavities and similar defects in welded joints of stainless steels and aluminum alloys, affecting their quality, directly depends on spatial weld position in laser welding. Reducing the angle of inclination from 90° to 0° during downhill and uphill welding of AISI 321 stainless steel in the pulse mode of laser generation leads to an increase in both the number of pores and their size. At the same time, defects in the form of pores are not observed in the continuous mode of laser generation. In laser welding of butt joints of AISI 321 steel, the flat and vertical weld positions are the most promising, as they provide the highest level of quality. In order to provide a stable formation of a high-quality butt joint of aluminum AMg6M alloy and to prevent the failure of laser equipment, the welding process should be carried out in a vertical uphill weld position.
关键词： different spatial position,aluminium alloy,stainless steel,quality,defects,porosity,laser welding
更新于2025-09-23 15:21:01
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Application of high power pulsed nanosecond fibre lasers in processing ultra-thin aluminium foils
摘要： This study is directed at developing a micro-scale laser scoring process and understanding the laser-material interaction in ultra-thin aluminium foils (160 ??m thickness). The research is carried out by the latest generation of nanosecond pulsed ?bre lasers manufactured by SPI Lasers. Presented comparative analysis of 70 W and 120 W laser types gives important insights for laser functionality and can provide recommendations for scalability of the process and quality assurance. High average power lasers were used to meet the requirement of high processing speed in aluminium foils. Scoring in aluminium foils was analysed using the fundamental laser-material interaction parameters that fully determine the way the material responds to the laser energy independent of the laser system. This approach permits transferring the results from the micro-scale laser process between various laser systems. Energy density and laser power density calculated for considered beam spot area at various frequencies were found to be the parameters that determine the scoring ablation depth in the range of 40 ??m–60 ??m. Microscopic examination of the ablation depth and score quality was carried out by an LED illumination 3D microscope. The SEM micrographs indicated minor growth of material debris from the ejected material.
关键词： Aluminium alloy,Scoring,Pulsed wave,Processing,Nanosecond ?bre laser,Ablation
更新于2025-09-23 15:21:01
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The impact of laser surface treatment on the microstructure, wear resistance and hardness of the AlMg5 aluminum alloy
摘要： Light metal alloys due to several unique properties such as low density and high corrosion resistance are increasingly used in various technical applications, where the automotive industry is one of the most important sectors. The automotive applications use mostly aluminum alloys, where the strength to density ratio of the material plays a crucial factor. Unfortunately, relatively low mechanical properties limit their applications for parts where a high surface hardness and wear resistance is expected. The classic heat treatment of aluminum alloys can only in some limited ranges improve the bulk material properties. Despite this, surface treatment with laser processing has developed significantly over the past 20 years. The laser beam treatment allows the introduction of a wide range of alloying elements to the surface layer of an aluminum alloy and thus, as a result of the precipitation of numerous intermetallic phases, significantly increases hardness, and abrasion resistance. The purpose of this work was to modify the aluminum surface layer using high-power fiber laser (HPFL). During this process, a mixture of titanium and iron powders (90/10 wt.%) was introduced onto the surface of the AlMg5 alloy. The microhardness tests carried out by the Vickers method and tribological tests showed a significant increase in mechanical properties in the entire volume of the obtained layer. Research on light and scanning microscopy revealed fragmentation of primary precipitates and the formation of numerous intermetallic phases rich in titanium and aluminum.
关键词： Aluminium alloy,Laser treatment,EDS analysis,Tribological properties,High power fibre laser
更新于2025-09-23 15:19:57
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Parametric Analysis of High Power Disk Laser Welding of 5052-H32 Aluminium Alloy
摘要： High power disk laser conducting welding of 2 mm thick AA 5052-H32 was performed within a process window and optimized for improved weld quality (i.e. penetration depth). The macrostructure of the weldment was investigated for the weld penetration depth at varying processing parameters using stereo zoom optical microscopy. The significance of the single effects and interaction effects of the parameters on the weld penetration depth was determined using ANOVA. Maximum weld penetration depth (1.71 mm) was achieved at laser power of 2600 W, welding speed of 0.03 m/s and focal position of -3.75 mm. At 95% confidence, only the welding speed –focal position interaction was found to contribute significantly to the weld penetration depth. The effect of the welding speed was most noticeable at low focal position (F < -3.9), that is, when the workpiece is further away from the focus. A linear regression mathematical model predicting the penetration depth of AA 5052-H32 disk laser weldments to an accuracy of 86% was developed and validated.
关键词： AA 5052-H32 Aluminium Alloy,Optimisation,Regression Model,Disk Laser Welding,ANOVA,Penetration Depth
更新于2025-09-16 10:30:52
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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