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Mechanism study on the effects of power modulation on energy coupling efficiency in infrared laser welding of highly-reflective materials
摘要： High-reflectivity of materials, such as magnesium, copper and aluminum, results in low thermal efficiency of their infrared laser welding processes. AZ31 magnesium alloy was selected to study the effects of power modulation on energy coupling efficiency in laser welding of highly-reflective materials. A model for the relationship between energy coupling efficiency and modulation parameters was obtained. The energy coupling efficiency in optimized modulated-power laser welding was about 1.58 times that in constant-power welding. The mechanism was explored by analyzing keyhole evolution and the resulted pressure distribution along keyhole wall during welding. The keyhole evolutions in laser continuous welding of common material (Q345 steel, reflectivity of 65%) and highly-reflective material (AZ31, reflectivity of 85%) were observed through high-speed imaging by utilizing a half sandwich method. The results indicated that the secret of improving energy coupling efficiency of laser welding process of highly-reflective materials through power modulation was the formation of a deep keyhole and its long life. When instantaneous power decreased from the peak, there was still enough recoil pressure at the bottom of keyhole to resist surface tension and hydrostatic pressure of liquid metal, which was the fundamental reason for the long time existence of keyhole with a large depth.
关键词： laser welding,magnesium alloy,recoil pressure,keyhole,highly-reflective materials,power modulation
更新于2025-11-28 14:24:20
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Laser welding of AZ31B magnesium alloy with beam oscillation
摘要： Circular beam oscillation was introduced to laser welding of 2 mm-thick AZ31 magnesium alloy. The appearance, microstructure and tensile properties of the welds were investigated. It was found that the low frequency about 50 Hz and the small radius about 0.5 mm are more beneficial to improve the weld appearance, under the given parameters of laser power 2 kW, welding speed 2 m/min and beam oscillating diameter 0.35 mm. The undercut defect and even the totally collapse of the weld appear when employing the frequency higher than 75 Hz or the radius larger than 1.5 mm. The microstructure evolution mainly reflects in the variation of the proportions of the equiaxed zone (PEZ) and the average grain size (SG). The PEZ decreases from 85% to 42% with the beam oscillating frequency increasing from 25 Hz to 100 Hz, while the SG reaches the maximum of 37.5 μm at 75 Hz. The PEZ decreases and the SG increases with the increase of beam oscillating radius. The results showed that the tensile strength and elongation are closely related to the PEZ, the SG and the twins. According to the experimental results, the relationship of oscillating parameters, microstructure, and tensile properties was established.
关键词： Laser oscillating welding,Magnesium alloy,Microstructure,Tensile properties
更新于2025-11-28 14:24:20
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Microstructural Characteristics of Laser Metal Deposited Magnesium Alloy AZ31
摘要： Up to now, only a limited amount of metallic materials is investigated for laser additive manufacturing (LAM). However, the demand to widen the application possibilities by enlarging the range of materials for LAM is growing fast. By now, titanium and aluminium alloys are in the focus of research. In contrast, magnesium alloys are rarely used in the field of additive manufacturing, although they possess a low density in combination with a high specific strength. Currently, magnesium structures are mainly produced by casting but during the last years, the use of wrought alloys also increased. A reason for the rare use of magnesium alloys for LAM technologies might be the high flammability of magnesium powders. This difficulty can be avoided by using magnesium wire for laser metal deposition (LMD). In the present study, the microstructural characteristics of a LMD processed AZ31 magnesium alloy are investigated. For this purpose, optical microscopy and scanning electron microscopy were used. With the help of EDX and EBSD analysis, a change of the chemical composition and micro texture with structure height was identified. The relationship of microstructure and local mechanical properties was investigated with the help of Vickers micro hardness testing. Based on the obtained results it can be concluded that the microstructural characteristics of laser additive manufactured magnesium alloys differ from those of titanium and aluminium alloys. Thus, a wider application spectrum of LMD and magnesium alloys can be opened up.
关键词： laser metal deposition,local mechanical properties,microstructure,magnesium alloy,wire,microtexture
更新于2025-11-28 14:24:20
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Wear and Corrosion Resistance of Al0.5CoCrCuFeNi High-Entropy Alloy Coating Deposited on AZ91D Magnesium Alloy by Laser Cladding
摘要： In order to improve the wear and corrosion resistance of an AZ91D magnesium alloy substrate, an Al0.5CoCrCuFeNi high-entropy alloy coating was successfully prepared on an AZ91D magnesium alloy surface by laser cladding using mixed elemental powders. Optical microscopy (OM), scanning electron microscopy (SEM), and X-ray diffraction were used to characterize the microstructure of the coating. The wear resistance and corrosion resistance of the coating were evaluated by dry sliding wear and potentiodynamic polarization curve test methods, respectively. The results show that the coating was composed of a simple FCC solid solution phase with a microhardness about 3.7 times higher than that of the AZ91D matrix and even higher than that of the same high-entropy alloy prepared by an arc melting method. The coating had better wear resistance than the AZ91D matrix, and the wear rate was about 2.5 times lower than that of the AZ91D matrix. Moreover, the main wear mechanisms of the coating and the AZ91D matrix were different. The former was abrasive wear and the latter was adhesive wear. The corrosion resistance of the coating was also better than that of the AZ91D matrix because the corrosion potential of the former was more positive and the corrosion current was smaller.
关键词： laser cladding,wear,AZ91D magnesium alloy,high-entropy alloy coating,corrosion
更新于2025-11-21 11:24:58
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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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Laser Welding of ZE41 Mg Alloy: Experimental Investigations on the Effect of Parameters and Nondestructive Testing
摘要： Laser beam welding is an essential metal joining method for magnesium and its alloys with their growing applications in automotive, aerospace, marine, etc. In this research paper, the experimental modelling for laser beam welding of ZE41 Mg alloy and the mechanical and metallurgical characterisation after welding are reported. The effects of weld scan speed and laser beam power on the weld geometry for bead on plates of ZE41 Mg alloy using a continuous-wave CO2 laser system were analysed in this work. The microstructure, hardness, and radiography analysis were discussed. The results indicate the in?uence of laser parameters and the validity of the regression equations developed for the optimisation of process parameters.
关键词： ZE41 magnesium alloy,Hardness,Optimisation,X-ray radiography,Laser beam welding
更新于2025-09-23 15:19:57
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The New Heat Source Model of AZ31B Magnesium Alloy Laser-TIG Hybrid Welding
摘要： A new heat source model consisted of inverted conical heat source and rotary Gauss body heat source is established using the CAE software for the keyhole effect of laser-TIG hybrid welding. The inverted conical heat source is used for analyzing the wide upper part of weld pool due to the rapid heat up by the laser and arc. The rotary Gauss body heat source model is used for analyzing the long and narrow lower part of weld pool formed by the laser. The result showed that, compared with other single source mode, this new heat source model may get a better simulation of the weld pool morphology, especially the inflection point near the keyhole. It provides a new method to predict the morphology and size of the weld pool of magnesium alloy laser-TIG welding.
关键词： shape of weld molten,keyhole effect,magnesium alloy,laser-TIG hybrid welding
更新于2025-09-16 10:30:52
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Application of acoustic emission and laser optoacoustics at various stages of defect formation during friction stir welding
摘要： This paper covers basic aspects of laser ultrasound and acoustic emission non-destructive testing methods in application of monitoring friction stir welds during its deformation and fracture. Stress-strain curves for such welds were obtained and the mechanical characteristics of welded joints of aluminum-magnesium alloy were determined. Using acoustic elastic effect levels of mechanical stresses were measured. Signals of acoustic emission, stimulated by one-axis loading, were registered and analyzed. It was established that acoustic emission during deformation and fracture of samples of welded joints is associated with the course of the process of plastic flow of the material. The nature of the distribution of acoustic emission parameters in the destruction of welded joints with defects has distinctive features. In conditions of one axis quasi static loading rate event count acoustic emission is the most informative parameter.
关键词： friction stir welding,laser optoacoustics,aluminum-magnesium alloy,acoustic emission,defect formation
更新于2025-09-16 10:30:52
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<i>In situ</i> spectroelectrochemical ellipsometry using super continuum white laser: Study of the anodization of magnesium alloy
摘要： This work shows the interest to use a real time, white laser-based ellipsometer to characterize a complex electrolyte|electrode interface during an electrochemical process in an aqueous-based medium. This method is proposed to probe electrochemical interfaces that are usually not suitable to the full extent application of ellipsometry due to great disturbance of the re?ected light ?ux provoked by gas evolution or roughness. In situ spectroelectrochemical ellipsometry combining such a visible super continuum ?ber laser-band source was not previously reported to the best of the authors’ knowledge. The setup was employed to monitor an electrochemical process whose mechanism was previously incompletely described: the prespark anodization regime of the plasma electrolytic oxidation process of the Mg alloy AZ91D in the 3M KOH electrolyte. Above the anodization voltage of 4 V, the side water oxidation reaction induced light diffusion that reduces re?ected light beam intensity. The process is monitored in an extended voltage range from 4 to 40 V and in an extended spectral range (495–800 nm). In the presented case, the use of a visible super continuum ?ber laser-band source enhanced the signal-to-noise ratio giving access to a deeper picture of the triplex layer structure during surface repassivation by monitoring the evolution of the outer, inner, and interfacial layers.
关键词： AZ91D,anodization,super continuum white laser,spectroelectrochemical ellipsometry,magnesium alloy
更新于2025-09-11 14:15:04