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High energy femtosecond laser peening of 2024 aluminum alloy
摘要： A femtosecond laser with a pulse energy of up to 100 mJ is used to investigate the feasibility of laser peening of a 2024 aluminum alloy that is widely used in aerospace industry. Laser beam directly irradiates the as-received aluminum sample surface in air without any protective coating for laser absorption and transparent overlay for plasma confinement. The effects of pulse energy, pulse duration and beam spot size on peening performance are studied. Optical microscope and SEM are used to examine the surface morphology of laser peened samples. Vickers hardness test is used to determine the microhardness on the surface. Residual stresses on the surface and at selected depths are measured using x-ray diffraction method. It is found that femtosecond laser can impart compressive residual stresses to a depth of more than 100 μm for this material, but the surface stress condition is not altered significantly.
关键词： residual stress,aluminum alloy,hardness,femtosecond laser,surface texture,laser peening
更新于2025-09-12 10:27:22
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Modulation of the local grain structure in laser beam welds to inhibit the propagation of centerline hot cracks
摘要： The morphology and the size of the grains of a weld result from the solidification rate and the temperature gradient during solidification. The heat input and the velocity of the welding process directly affect these quantities. The laser power, the welding velocity and the beam diameter were periodically modulated to achieve a periodical change of the solidification conditions during welding. It leads to a continuous change of the type of grain structure over the welded length. The metallographic analysis of welds in close edge position shows the periodical interruption of centerline cracks at local changes of the grain structure.
关键词： Laser Beam Welding,Grain Structure,Aluminum Alloys,Hot cracks
更新于2025-09-12 10:27:22
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Study the Effect of Changing the Surface Roughness and the Laser Focus Distance to the Aluminum Appearance using Picosecond Laser
摘要： Picosecond laser device is used to treat Aluminum samples, the appearance of the treated samples is affected by the variation of laser focus distance and the samples surface roughness. Samples with smoother surface before laser treatments show dark colors and high increase in surface roughness after laser treatments, while samples with rougher surfaces before laser treatments show brighter colors with slightly change in surface roughness after the laser treatments. The surface texture, topography, and roughness of the treated samples is characterized to identify the mechanism driving appearance change. The characterization results indicate that size and shape of laser processing induced microscale cavities on the surface may account for the differences in samples appearance.
关键词： Aluminum Appearance,Picosecond Laser,Focus Distance,Surface Roughness
更新于2025-09-12 10:27:22
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Microstructure and hardness evolution of laser metal deposited AA5087 wall-structures
摘要： Wire-based laser metal deposition enables to manufacture structures with very high deposition rates in comparison to powder-based laser additive manufacturing. However, this advantage is generally accompanied with a high energy input. Thus, an accumulation of heat within the structure can result. In addition, the heat conduction conditions can also change with increasing structure height, leading to inhomogeneous microstructural formation along the part. The present study deals with the evolution of the microstructure and hardness in laser metal deposited AA5087 wall structures. In this regard, two samples processed at adapted parameters for different deposition rates are investigated.
关键词： aluminum alloy,microstructure,laser additive manufacturing,microhardness,laser metal deposition
更新于2025-09-12 10:27:22
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Fatigue crack growth behavior of laser-shock processed aluminum alloy 2024-T3
摘要： Laser shock processing (LSP) is a surface modification technique aimed at enhancing the resistance to wear, corrosion and fatigue of structural alloys. Recently, LSP without coating (LSPwC) has been gaining ground, using lasers with lower energies, shorter pulse duration, smaller laser spots and higher surface coverage per shot. In the present work, LSPwC treatment was performed in both sides of pre-cracked compact tension specimens of aluminum alloy 2024-T3. A pulsed (9 ns) Nd:YAG laser system operating in the second harmonic (532 nm) at 10 Hz repetition rate and with pulse energy of about 270 mJ was positioned with a 500 mm focal distance lens in order to conduct LSPwC with an estimated power density of 5.2 GW/cm2 and two distinct overlapping rates: 50% and 75%. The objective of the work was to investigate the effect of the LSPwC and cyclic load condition on the crack closure and fatigue crack growth (FCG) behavior shown by the samples. Constant amplitude FCG tests were performed with two distinct load ratios: R = 0.2 and R = 0.5. A small increase in the crack closure loads (Pcl ? 1.1-1.2 Pmin) and in the number of cycles to crack propagation was evinced for the specimens tested at R = 0.2 compared to the untreated ones, whereas negligible effect was observed in the R = 0.5 tests. Besides, the obtained results indicate that the increase in overlapping rate is not effective for the adopted LSPwC conditions.
关键词： Laser shock processing,Fatigue crack growth,Aluminum alloy 2024
更新于2025-09-12 10:27:22
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Femtosecond Laser Written Depressed-Cladding Waveguide 2 × 2, 1 × 2 and 3 × 3 Directional Couplers in Tm3+:YAG Crystal
摘要： Ion-doped crystal-based compact devices capable of beam splitting and coupling are enthralling for a broad range of classical and quantum integrated photonics applications. In this work, we report on the fabrication of depressed-cladding waveguide 2D 2×2, 1×2 and 3D 3×3 directional couplers in Tm3+:YAG crystal by femtosecond laser writing. The performances of the couplers are characterized at 810 nm, showing single-mode guidance, polarization independence, ?nely matched splitting ratios. These results open up new opportunities in the bene?cial fabrication of 3D circuits and devices in crystals.
关键词： crystal,femtosecond laser writing,directional coupler,depressed-cladding waveguide,integrated photonics,yttrium aluminum garnet,quantum memory
更新于2025-09-12 10:27:22
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Simulation of laser-driven cratering experiments on aluminum
摘要： After a brief description of the physical principles involved in the cratering process, the authors present a specific methodology to simulate laser-driven cratering experiments performed with a long pulse duration (100 ns) and a small focal spot diameter (220 μm). This methodology can be divided into two steps. First, the 2D-axisymmetrical pressure field generated by the laser on the target is determined from laser parameters. Second, this pressure is applied on the surface of the target in a Eulerian simulation. In order to validate this methodology, the authors simulate a laser shot on a thin aluminum target whose rear surface velocity is recorded by a VISAR (Velocity Interferometer System for Any Reflector). Once validated, they use the methodology to simulate laser-driven cratering experiments on semi-infinite aluminum targets. Numerical results are compared to experimental measurements of the craters. Although slight differences are pointed out and discussed, the proposed methodology is well adapted to simulate craterization laser shots.
关键词： laser,simulation,crater,aluminum
更新于2025-09-12 10:27:22
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Channeled Implantations of p-Type Dopants into 4H-SiC at Different Temperatures
摘要： Channeling of B and Al ions in 4H-SiC(0001), has been investigated by secondary ion mass spectrometry (SIMS). Ion implantations have been performed between room temperature (RT) and 600 °C at various fluences. Before implantation, the major crystal axes were determined and the sample was aligned using the blocking pattern of backscattered protons. As expected, the depth distribution of the implanted ions along a crystal direction penetrates much deeper compared to non-channeling directions. At elevated temperatures, the channeling depth for 100 keV Al-ions is decreased due to lattice vibrations. For 50 keV B-ions, the temperature effect is minor, indicating a smaller interaction between target atoms and B. Simulations has been performed using SIIMPL, a Monte Carlo simulation code based on the binary collision approximation, to predict experimental data and get a deeper insight in the channeling process.
关键词： Channeling,Boron,SIMS,Ion implantation,Aluminum
更新于2025-09-12 10:27:22
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Light Metals 2016 (TMS/Light) || TiB <sub/>2</sub> Particle Detection in Liquid Aluminum via Laser Induced Breakdown Spectroscopy
摘要： Experimental Because aluminum alloy castings are becoming commonplace for critical applications in the automotive and aerospace industries, tight control over the cleanliness of the melt (mitigation of solid particle inclusions) and microstructure must be achieved. In order to control cleanliness, it must first be well defined and measured. Very few techniques exist in industry that can quantitatively measure in-situ. Laser-induced breakdown spectroscopy (LIBS) is presented as a promising technique to quantify solid particles, desired or undesired, in aluminum melts. By performing LIBS with subsequent statistical analysis on liquid Al with varying amounts of TiB2 particles, calibration curves for B and Ti were generated.
关键词： Inclusions,LIBS,Metal Cleanliness,Liquid Aluminum
更新于2025-09-12 10:27:22
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p-type doping of Ge by Al ion implantation and pulsed laser melting
摘要： Germanium recently attracted a renewed interest for its potential applications in several fields such as nanoelectronics, photonics, plasmonics, etc., but well-known issues about doping at high concentration and controlling impurity profiles prevent its integration in technology. To this purpose, p-type doping aluminum ion implantation followed by pulsed laser annealing in the melting regime has been investigated for the first time. In particular, two different regimes have been studied, in order to explore the limit of incorporation for such a method: 6.4 × 1014 Al/cm2 and 4.2 × 1015 Al/cm2, both at 25 keV, corresponding to concentrations below and above the solid solubility, respectively. We found that in the former case, oxygen contamination precludes full activation (< 60 %), as suggested by Raman characterizations. Besides, secondary ion mass spectrometry evidences pronounced out-diffusion and pile-up of the dopant near the surface. In the letter case, remarkable (～ 1 × 1020 Al/cm3), although partial (～ 30%), electrical activation is obtained, independently on O occurrence. Therefore, O-Al and Al-Al clustering are proposed as concurrent mechanisms, limiting full activation at high implanted dose. Nevertheless, the samples display good crystalline quality and, surprisingly, a significant thermal stability (up to 600° C).
关键词： Laser processing,Germanium,Doping,Ion Implantation,Aluminum
更新于2025-09-12 10:27:22