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Study on ?′-ferrite evolution and properties of laser fusion zone during post-weld heat treatment on Al-Si coated press-hardened steel
摘要： Laser welding of Al-Si coated press-hardened steel (PHS) was still a challenging due to the formation of ?-ferrite in the fusion zone. However, it was ambiguous on the ?-ferrite evolution during post-weld heat treatment (PWHT). In this study, Al-Si coated PHS was welded by laser ?ber and then heat-treated at various temperatures (650 ?C, 950 ?C and 1050 ?C), and the microstructure evolution was investigated by in situ-observation. Mechanical properties and formability of welded joints was analyzed. The results showed that ?-ferrite did not go through phase transformation during PWHT regardless of any temperature, but with a grain boundary ?atted and movement. The presence of coarse ?-ferrite after PWHT was the responsible for the decreasing of tensile strength and formability of welded joints. The initiation crack was easy to generate in the phase interface between ?-ferrite and martensite to form a local brittle fracture zone ?nally. This study results provides a new theoretical criterion for the properties improvement on the laser welding of PHS without removing Al-Si coating.
关键词： Laser welding,Post-weld heat treatment,Al-Si coating,Press hardened steel ?-ferrite
更新于2025-09-23 15:21:01
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Improvement of the Laser-Welded Lap Joint of Dissimilar Mg Alloy and Cu by Incorporation of a Zn Interlayer
摘要： During pulsed laser welding of AZ 31B magnesium (Mg) alloy and T2 pure copper (Cu), Cu2Mg and Mg2Cu are generated, but the bonding ability of the two compounds is usually weak, resulting in low strength. In order to improve the joint of two dissimilar metals, a zinc interlayer was inserted between the Mg alloy and Cu, and the effects of the thickness of the Zn interlayer on the microstructure and properties of the joint were studied. The fused zone consisted of Cu2Mg and MgZn, and, according to first-principles calculation, in the same energy range, the area enclosed by the density of the state curve of MgZn was larger than that of Cu2Mg. Hence, the bonding ability of MgZn was better than that of Cu2Mg, and MgZn improved the strength of the welded joint. The most advantageous thickness of the Zn interlayer was 0.1 mm, and the shear strength was 48.15 MPa that was 161% higher than that of the directly welded Mg/Cu joint.
关键词： interlayer,first-principles calculation,magnesium alloy,laser welding,dissimilar metals
更新于2025-09-23 15:21:01
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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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Study on the Microstructure and Properties of Al/Cu Laser Filled Solder Joint
摘要： Using IPG-YLS-4000 fiber laser to weld T2 copper plate and LY16 aluminum alloy plate, using Zn-10%Al flux cored wire as filler material, the microstructure of the joint was observed and analyzed by SEM and EDS, and the effects of laser power, welding speed and welding line energy on the mechanical properties of the joint were studied. The results show that the joints are mainly divided into copper side brazing area, weld center area and aluminum side fusion welding area. Among them, there are two interface reaction layers composed of intermetallic compound (IMC) in the copper side brazing area, the first layer is CuZn compound in the form of strip, and the second layer is Al2Cu phase in the form of shoot. The central area of the weld is mainly composed of massive α-Al phase and branched β-Zn phase. The tensile strength of the joint increases first and then decreases with the increase of laser power, welding speed and welding line energy. The thickness of IMC layer grows linearly with the increase of line energy. The best process parameters: when the laser power is 2200 W, the welding speed is 0.9 m/min, the welding line energy is 1446.67 J/cm, the IMC layer thickness is 10.11 μm, and the tensile strength reaches the maximum value, 252.6 MPa.
关键词： intermetallic compound,Al/Cu laser welding,microstructure,mechanical properties,Zn-10%Al flux cored wire
更新于2025-09-23 15:21:01
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Experimental Study of Thermomechanical Processes: Laser Welding and Melting of a Powder Bed
摘要： In this study, an experimental approach was developed to analyze and better understand the laser welding and melting of a powder bed process. Different optical diagnostics tools (high-speed camera, infrared camera, pyrometer, etc.) were applied to measure different physical quantities (molten pool morphology, temperature ?eld, residual stresses, and distortions). As a result, measurements during the laser welding process facilitated the building of a database of experimental results (experimental benchmarks). The study of the melting of a powder bed enabled a better understanding of the physics related to the formation and behavior of the molten pool. These results can be used by researchers to improve and validate numerical simulations of these processes.
关键词： optical diagnostics,molten pool,melting of a powder bed,residual stresses,laser welding,temperature field
更新于2025-09-23 15:21:01
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Theoretical study of influence of electromagnetic stirring on transport phenomena in wire feed laser beam welding
摘要： The additional element from the filler wire in the laser beam welding is usually distributed inhomogeneously in the final weld due to the high solidification rate of weld pool. It has been found that the electromagnetic stirring produced by an external oscillating magnetic field can enhance the material mixing in the weld pool to achieve a more uniform element distribution. However, the magnetic field has a highly nonlinear and multicoupled interaction with the weld pool behavior, which makes the quantitative explanation of the physical mechanism difficult. In this study, the effect of electromagnetic stirring on the transport phenomena in the wire feed laser beam welding is investigated by a numerical modeling. A 3D transient multiphysical model considering the magnetohydrodynamics, heat transfer, fluid flow, keyhole dynamics, and element transport is developed. The multiple reflections and the Fresnel absorption of the laser on the keyhole wall are calculated using the ray tracing method. The numerical results show that a Lorentz force produced by the oscillating magnetic field and its induced eddy current gives significant influence on the transport phenomena in the molten pool. The forward and downward flow is enhanced by the electromagnetic stirring, which homogenizes the distribution of the additional elements from a nickel-based filler wire in a steel weld pool. The numerical results show a good agreement with the high-speed images of the molten pool, the fusion line from the optical micrograph, and the element distribution from the energy dispersive x-ray spectroscopy. This work provides a physical base for the electromagnetic-controlled laser beam welding and some guidance for the selection of electromagnetic parameters.
关键词： magnetohydrodynamics,molten pool dynamics,laser beam welding,element transport
更新于2025-09-23 15:21:01
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The protective capability of the laser welded armour steel plates
摘要： Despite the intensive development of plastics and composite materials in the case of armours employed to protect vehicles, armour steel remains a material commonly and effectively used. This is especially evident in the base armour of armoured vehicles, where the body is made of welded armour steel plates. However, the area of joining both the weld and the heat affected zone are sensitive areas with the reduced protective capability. In the case of laser welding in comparison with methods such as shielded metal arc welding and gas metal arc welding, it is possible to narrow down the above mentioned areas. The paper presents the results of research on the protective capability of welded zone of armour steel plates with a hardness of 500 HB. In the first part of the work, in order to select the proper parameters for the bonding process, different connection variants were made and their microstructure and selected mechanical properties were analysed. After selecting the best variant of the welding process, samples (200 mm (cid:2) 200 mm) consisting of two welded plates with dimensions 100 mm (cid:2) 200 mm were made for testing. The thickness of the plates was selected in such a way that in the areas outside the bonding zone, the lack of complete perforation by the projectiles used in the tests is guaranteed. The samples were shot at the weld location and at different distances from the weld to verify, for the chosen method of joining steel plates, if the welded armour loses its protective capability and, possibly, how wide this area may be.
关键词： ballistic tests,Armour steel,laser welding,quenched and tempered steel
更新于2025-09-23 15:21:01
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Processing of Keyhole Depth Measurement Data during Laser Beam Micro Welding
摘要： Analysing the quality of weld seams is still a challenging task. An optical inspection of the surface is giving limited information about the shape and depth of the weld seam. An application for laser beam welding with high demands regarding the weld depth consistency is the electrical contacting of battery cells. The batteries themselves have a limited terminal or case thickness that must not be penetrated during the welding process to avoid leakage or damage to the cell. That leads to a minimum weld depth to ensure the electrical functionality, and a maximum weld depth indicated by the case thickness. In such applications, a destructive analysis is not suitable which leads to the demand for a non-destructive measurement during the process. Using a coaxial, interferometric measurement setup, the keyhole depth during the deep penetration welding is measureable. For a keyhole with a depth of a couple of millimetres, such a system is commercially available. In micro scale, however, these systems are facing several challenges such as scanning systems, small spot diameters of a few tens of micrometres and narrow keyholes. This study contains an investigation of an interferometric measurement of the keyhole depth and the suitability for laser micro welding. Therefore, the data processing of the achieved measurements is investigated, and the results are compared with the depth measurement of metallographic analysed samples. Stainless steel is used to investigate the behaviour and the stability of developed data processing strategy and the resulting depth values.
关键词： Laser welding,battery,copper,spatial power modulation,aluminium,keyhole depth measurement
更新于2025-09-23 15:21:01
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[Laser Institute of America ICALEO?? 2014: 33rd International Congress on Laser Materials Processing, Laser Microprocessing and Nanomanufacturing - San Diego, California, USA (October 19a??23, 2014)] International Congress on Applications of Lasers & Electro-Optics - Possibilities of improving weld seam quality in laser welding of aluminum die cast
摘要： The process of aluminum die-casting produces near-net-shape, complex and thin-walled prefabricated parts of aluminum that is more widely applied in all areas of the industry because it has economic advantages compared to other processes in productivity. The technique mostly used in the molding process of aluminum die-casting products is fusion welding, which shows multiple problems: The safe production of pore free welding seams requires an expensive optimization all over the die-casting process as well as the choice of a qualified welding process. Compared to arc welding, the beam welding processes are characterized by high welding speeds, low heat input and consequently by small heat-affected zones and minimal distortion. Thus, the beam procedures are suitable in particular for components in which narrow and deep weld seams are required. Exemplary, aluminum die cast housings are such parts. However, the welds have to meet the desired requirements on the tightness there. This is a great challenge because aluminum die cast tends to pore formation and melt ejection due to its production-related gas content. Respect to the achievable weld seam quality, in particular, electron beam welding exhibits best results. This is due to the process management under vacuum in the range of p = 10-3 hPa, which makes it possible to eliminate atmospheric influences and generally contributes to better degassing. An alternative beam welding procedure is laser beam welding. Compared to the EB welding, however, laser beam weldings of aluminium die cast have an increased porosity. In this paper, different possibilities are presented by which an improvement of weld seam quality in laser beam welding of aluminum die casting can be achieved. Experiments with different laser optical configurations, as well as varying process parameters influence the formation of pores in a considerable extent. In addition, the ambient pressure is a decisive parameter to improve the weld quality. The welding process is more and more stable and the formation of pores is clearly suppressed by decreasing pressure.
关键词： weld seam quality,aluminum die cast,porosity,vacuum,laser welding
更新于2025-09-23 15:21:01
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Interface Kinematics of Laser Impact Welding of Ni and SS304 Based on Jet Indentation Mechanism
摘要： With the application of high-velocity impact welding (HVIW) technology, the research on the mechanism of the formation and evolution of interface waveforms has become an important research direction in HVIW. Understanding the mechanism of interface motion can help control and improve HVIW. Laser impact welding (LIW), a branch of HVIW, lacks research on the formation and evolution of interface waveforms. Therefore, LIW experiments of Ni and SS304 are carried out. The jet indentation mechanism and the smoothed particle hydrodynamics method are used to simulate and analyze the formation and evolution of the LIW interface waveform. Results show that the interface materials exhibit ?uid behavior during LIW. The jet indentation mechanism can explain the formation and evolution of waveforms in LIW. Jet velocity, normal stress, and ?yer horizontal welding speed are the main factors a?ecting the variation of the interface waveform size in LIW. At the collision point, the smaller the horizontal welding speed of the ?yer, the larger the wavelength; the smaller the jet velocity, the smaller the amplitude. In addition, the propagation of the normal stress deviating from each other at the welding interface along the welding direction is the fundamental cause of springback and cracking.
关键词： SS304,Ni,Laser impact welding,Smoothed particle hydrodynamics,Jet indentation mechanism,Interface waveforms
更新于2025-09-23 15:21:01