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Morphology and magnetic properties of grain-oriented steel scribed using different picosecond lasers
摘要： Micro-scribing experiments were conducted to investigate the characteristics of the associated ablative behavior and the improvements to the magnetic properties of grain-oriented steel using both a 532 nm and a 1064 nm wavelength ultra-fast picosecond laser. Ablative morphological characteristic analysis and elemental analysis were carried out using a 3D confocal microscope, a scanning electron microscope, and energy-dispersive spectroscopy. The damage mechanisms were analyzed by comparing the ablation morphologies. Furthermore, an iron loss tester and magnetic domain observation instrument were used to analyze the dynamic hysteresis loop, macroscopic magnetic property parameters, and to observe the microscopic structure of the magnetic domains. The magnetization behavior, loop characteristics, and magnetic domain refinement mechanisms were discussed. The results indicated that the magnetic domains were clearly refined and that the magnetic properties were significantly improved after picosecond laser scribing of the grain-oriented steel. The sample scribed using an ultra-fast wavelength 532 nm laser was more effectively scribed: the magnetic domain was slightly more refined, the iron loss was reduced by 15.73%, the coercivity was reduced by 24.42%, the residual magnetism was reduced by 20.8%, and the relative permeability was increased by 10.3%. The surface was of a high quality, but there were traces of stress damage caused by high-pressure steam in the scribed area. The 1064 nm wavelength ultra-fast laser clearly showed the effects of heat accumulation in the scribed area. Defects due to thermal damage were more common. The improvement to the macroscopic magnetic properties depended largely on the surface quality of the scribing and the penetration depth of the residual stress in the sample.
关键词： Magnetic domains,Laser surface treatment,Scanning electron microscopy,Iron core loss,Magnetic properties,Grain-oriented silicon steel
更新于2025-09-23 15:21:01
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Morphological and Chemical Characterization of Laser Treated Surface on Copper
摘要： Electron multipacting and electron cloud have been identified as being the major limiting factors for the beam quality or for the cryogenic system of high-intensity positive particles accelerators. Among conditioning operational techniques and other surface structuration techniques used to decrease the Secondary Electron Yield (SEY) of surfaces, laser surface treatment is a promising method to treat in situ and at atmospheric pressure copper surface of the vacuum chamber. Here, pulsed laser irradiation of copper in parallel lines pattern led to the local ablation and deposition of aggregates of copper particulates on the surface. Tests undertaken at CERN have shown that the modification of the surface morphology by creating roughness at different scales induces a decrease of the SEY by geometrical effects. Nevertheless, the mechanical strength and dust generation of the treated surface have not been addressed yet. In this work, a qualitative analysis of the multi-scale description of the surface morphology was carried out. Scanning Electron Microscopy (SEM), Focused Ion Beam (FIB), Transmission Electron Microscopy (TEM) and Energy Dispersive X-ray Spectroscopy (EDS) were used to investigate morphological characterization such as size and shape of the particulates, chemical composition, metallographic structures and phase transformation on the laser-processed surface. SEM and FIB examinations showed that the surface morphology depends on the local laser energy irradiating the surface and especially, relatively to the ablation threshold. TEM analysis revealed chemical composition and crystalline configuration of the treated material and helped to identify the laser modified and oxidized areas. A variety of superficial structures were observed. Potential vulnerable structures have been identified as oxidized matter redeposited on the ablated near surface. Material continuity and composition play a major role in the mechanical integrity of the generated surface morphology. The adherence of the created structures was assessed analyzing the origin of the dust extracted after mechanical stress.
关键词： microstructural observations,morphological characterization,laser surface treatment,surface structuration
更新于2025-09-16 10:30:52
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Microstructural characterization of Inconel 718 alloy after pulsed laser surface treatment at different powers
摘要： An annealed Inconel 718 alloy was surface-treated by pulsed laser at three different powers (100, 50 and 25 W). Microstructural changes induced by the laser treatments were characterized by use of electron backscatter diffraction and electron channeling contrast imaging techniques. Results show that both annealing twins and strengthening precipitates profusely existing in the as-received specimen are dissolved at elevated temperatures during the laser irradiation. Meanwhile, in the melting zone (MZ), densities of low angle boundaries (LABs) are greatly increased with a large number of Laves phases preferentially distributed along such LABs. For different specimens, widths and depths of their MZs are found to be gradually reduced with decreasing the laser powers. Orientation analyses reveal that the columnar grains in the MZ of the 100 W specimen could inherit orientations existing in the matrix while lower laser powers promote the formation of more nuclei with scattered orientations to grow to be granular grains in the MZ. Hardness tests reveal that the MZs of all laser-treated specimens are softer than the matrix probably due to both precipitate dissolution and grain coarsening.
关键词： pulsed laser surface treatment,hardness,grain boundaries,Inconel 718 alloy,electron backscatter diffraction
更新于2025-09-16 10:30:52
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A contribution to laser cladding of Ti-6Al-4V titanium alloy
摘要： A wear resistant coating was successfully made on an annealed Ti-6Al-4V titanium alloy by laser surface cladding using 60 wt.% WC + wt.% 40 NiCrBSi powder blends. Coaxial laser cladding was performed by means of Yb:YAG disk laser with a 3-KW continuous wave. Different laser interaction times were attempted to get the optimal conditions for promising mechanical properties. The new contribution was to accomplish larger clad layer thickness with applying the shortest possible laser interaction time that can achieve superior clad layer properties. This will decrease energy consumption with an expected money saving which is an essential factor for successful engineering solutions. A high powder ?ow rate of 20 g.min(cid:1)1 was intended in order to obtain a thick, nonporous and crack free clad layer. The clad samples were subjected to thorough microstructure investigations, in addition to microhardness and wear evaluation. The coating so produced exhibits multiple hardness values and exceptional wear resistance under adhesive/sliding wear conditions. The obtained results expose clad layer with superior quality that was achieved at a laser interaction time of 0.3 s. An enhancement in the microhardness values of the clad layers by more than fourfold was attained and the wear resistance was thus signi?cantly improved.
关键词： coaxial laser cladding process,titanium alloy,laser powder cladding,laser interaction time,microhardness,laser surface treatment,wear resistance
更新于2025-09-12 10:27:22
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Effect of adherend deflection on lap-shear tensile strength of laser-treated adhesive-bonded joints
摘要： Laser surface treatment was used as a surface preparation method for adherend prior to adhesive bonding, which significantly improved the fracture mode from mixed to cohesive and consequently increased the lap-shear tensile strength by 27.5% and 28.2% for aluminum alloys AA7075 and AA6022 adhesive-bonded joints, respectively. Nevertheless, the laser-treated AA7075 joint exhibited a ~14% higher strength compared to laser-treated AA6022 joint although both joints showed cohesive fracture modes, which was attributed to smaller adherend deflection of laser-treated AA7075 joint than that of laser-treated AA6022 joint. Digital image correlation technique was applied to monitoring the deflections of laser-treated AA7075 and AA6022 joints during lap-shear tensile testing, and the stress analysis of adhesive-bonded lap-shear joints was conducted by finite element simulation. It was found that the deflection angle of the laser-treated AA6022 joint reached to 6.1° at the peak tensile load and was ~69% larger than that of laser-treated AA7075 joint (i.e. 3.6°), which resulted in a mixed stress state with higher peel stress (i.e. ~8 MPa) on edges of adhesive bonding region and consequently led to a premature fracture due to the low peel resistance of adhesive-bonded joints. Furthermore, the effect of decreased adherend deflection on lap-shear tensile strength was investigated, and a linear increase of lap-shear tensile strength was found with the decrease of deflection angle for adhesive-bonded joints showing cohesive fracture modes.
关键词： finite element stress analysis (C),lap-shear tensile strength (C),laser surface treatment (B),aluminum alloys (B),adherend deflection
更新于2025-09-12 10:27:22
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Effect of Different Forms of Application of a Laser Surface Treatment on Fatigue Crack Growth of an AA6013-T4 Aluminum Alloy
摘要： This work analyzes the effect of surface-localized laser heating treatment on the fatigue crack growth (FCG) rate on region II of the sigmoidal da/dN 3 DK curve of an aerospace-grade AA6013-T4 aluminum alloy sheet with 1.3 mm thickness. The in?uence on microstructure changes is also evaluated. Aiming to improve the FCG resistance without changing the mechanical behavior of the alloy, a Yb:?ber laser beam is defocused to generate a laser spot diameter of 2 mm, using 200 W power and a laser speed of 2 mm/s. Two laser lines are applied over fatigue C(T) specimens in two different forms: on only one and on both lateral specimen surfaces. Guinier–Preston zones, dispersoids and coarse constituent particles are found on the base material. On the heat-treated material, the same precipitates and also b￠ and Q￠ precipitates are found. These microstructural variations due to the laser thermal cycle, together with the presence of induced compressive residual stresses, improved the fatigue behavior of the material. The FCG retardation is optimized when two laser lines were applied on both lateral surfaces of the specimen.
关键词： aluminum alloy,microstructure,fatigue crack growth,residual stresses,laser surface treatment
更新于2025-09-11 14:15:04
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How the Laser Beam Energy Distribution Effect on Laser Surface Transformation Hardening Process; Diode and Nd:YAG Lasers
摘要： The laser surface transformation hardening (LSTH) of AISI 4130 steel by 1600 W high power diode laser (HPDL) and 700 W Nd:YAG lasers were investigated in this present study. The distribution influence, and the lasers beam shape; Top-hat in the HPDL and Gaussian distribution in the Nd:YAG laser, have been studied on the geometrical dimensions, and micro-hardness in hardened area (i.e.; depth, width, and angle of entry of hardened profile), micro-hardness deviation (MHD) from the row steel in geometric dimensions, and the ferrite’s percentage in hardened layer center. Microstructure evaluation of the laser hardened areas were performed by FE-SEM and optical microscopy. Based on the results, maximum hardness was created with the HPDL, and the geometrical dimension was more than the Nd:YAG laser. Also, MHD, and minor phase of ferrite in the HPDL laser surface hardening than the hardened layer in Nd:YAG laser, which is related to the higher laser absorption. Results show that, the hardened zone of HPDL is about 698 HV0.1 with 1.02 mm depth, while for Nd:YAG laser is about 698 HV0.1 with 0.98 mm depth. Comparing the results with the furnace hardening heat treatment (FHT) demonstrated that the hardness in diode laser and Nd:YAG laser hardening are 1.38 and 1.22 times of the hardness in FHT, respectively.
关键词： Industrial lasers,AISI 4130 low alloy carbon steel,Beam shape,Laser surface treatment
更新于2025-09-11 14:15:04