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Eliminating continuous grain boundary α phase in laser melting deposited near β titanium alloys by heat treatment
摘要： Continuous grain boundary α phase (αGB) is widely present in laser melting deposited near β and β titanium alloys, and it can lead to intergranular fracture and low ductility. Because of the preferential nucleation and growth of α phase at β grain boundaries, the continuous αGB cannot be effectively eliminated by traditional heat treatment. Thus, in this study, we develop a new heat treatment including beta solution + ultra-slow furnace heating up + traditional heat treatment, to eliminate continuous αGB in laser melting deposited Ti-5Al-5Mo-5V-1Cr-1Fe near β titanium alloy, and the microstructures and tensile properties are investigated. The results indicated that, after beta solution + normal heating up + traditional heat treatment, the continuous αGB still exists, and the elongation is still low about 7.5%. However, after beta solution + ultra-slow heating up + traditional heat treatment, there are almost no continuous αGB, and the elongation increases to 15.2%. The mechanism about the αGB formation during ultra-slow heating up process is simply revealed. Furthermore, this new heat treatment is also suitable to eliminate continuous αGB for laser melting deposited Ti17 alloy.
关键词： ductility,continuous grain boundary α phase,laser melting deposition,heat treatment,near β titanium alloys
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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Numerical modelling and experimental validation of thermal history of titanium alloys in laser beam melting
摘要： During selective laser melting processes parts will heat up with each layer depending on the geometry and surrounding powder material. This leads to process boundary conditions that are not certainly defined and can induce unstable melt pool sizes. These will have an influence on surface roughness and dimensional accuracy. One way to deal with this is an individual adaptation of process parameters, but without knowing the exact thermal boundary conditions in each layer one will not be able to adapt the parameters properly. In this paper a model for prediction of the macroscopic temperature history is presented and experimentally calibrated. A sample with characteristic features like overhanging’s was designed. These samples were produced by selective laser melting and simultaneously monitored by an infrared camera to calibrate the boundary conditions of a numerical model. This lays the foundation for part individual adaption of process parameters to improve the quality of SLM parts.
关键词： Experimental Validation,Numerical Modelling,Titanium Alloys,SLM
更新于2025-09-12 10:27:22
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Analysis of a Ni-Fe-Cr-Mo-Si hardfacing alloy manufactured by laser cladding: influence of the iron content on the wear resistance properties
摘要： In this article, we present an ongoing study on a Ni-Fe-Cr-Mo-Si based alloy, as one of the potential cobalt free hardfacing materials. Here, we analyze the effect of the variation of iron content on microstructure and wear property that is induced by a controlled dilution the 316L substrate, or by direct addition. First, we present the state of the art on the proposed Ni-Cr-Mo-Si based alloy. Then, the laser cladding setup is presented and the process parameter map search of the Ni-Fe-Cr-Mo-Si based alloy too. Then, iron is added to the base Ni-Cr-Mo-Si alloy by direct fusion of the powders coming from two different powder feeders and directly blended into the coaxial nozzle used. Finally the samples are analyzed in iron content, microhardness and microstructure. The tribology tests of the samples exhibit a clear change in wear behavior with the iron content and an improvement at a certain level of iron.
关键词： Tribology,Nickel Base Alloys,Laser Cladding,Hardfacing Materials,Nuclear Energy,Wear resistance
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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Microstructure development in Pulsed Laser Welding of Dual Phase Steel to Aluminium Alloy
摘要： Lap joining of aluminium 6061 and dual phase (DP 600) steel was carried out in pulse welding mode using a high power diode laser. The effect of laser parameters (laser power, scanning speed and pulse duration) on the microstructural evolution during conduction welding was studied. The large difference in thermal and physical properties of DP 600 and Al 6061 alloy results in the formation of brittle intermetallic phases along the interface of the weld zone. At a laser power of 4 kW, scanning speed of 5 mm/s and pulse duration of 10 ms the thickness of the intermetallic phase formed was found to be reduced i.e. in the range of 1- 7 μm. The porosity in the weld zone were mainly due to the entrapment of the zinc vapors during welding because of its low vaporization temperature compared to DP 600 and Al 6061 alloy. Microstructural characterization of the intermetallic phases was done using scanning electron microscopy, X-ray diffraction and the phase composition were characterized using energy dispersive spectroscopy. The micro-hardness testing was to evaluate the mechanical properties of the lap joint. A maximum hardness of 461 HV was observed along the weld- aluminium interface owing to the presence of hard and brittle Fe2Al5 and FeAl3 intermetallic phases.
关键词： Dual phase steel,Intermetallic phases,Pulsed laser welding,Aluminium alloys
更新于2025-09-12 10:27:22
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Computer aided design of the laser dieless drawing process of tubes from magnesium alloy with take into account ductility of the material
摘要： Paper is devoted to the laser dieless drawing of the tubes made of magnesium alloy ZEK100. Important limitation of this process is a low ductility of magnesium alloys. The purpose of this work was the development and implementation into the FEM code, the ductility model of ZEK100 magnesium alloy and experimental validation of proposed methodology of process design. Ductility and flow stress models were developed based on tension and compression tests in temperature interval 20-350 °C. As result of this work, the technological diagrams for determination of diameter of tube after laser dieless drawing process were obtained.
关键词： Ductility,Dieless drawing,Tube,Magnesium alloys
更新于2025-09-12 10:27:22
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Fracture behaviour of alloys for a new laser ranged satellite
摘要： A new laser-ranged satellite called LARES 2 (Laser Relativity Satellite 2) has been recently designed for accurate tests of Einstein’s theory of General Relativity and space geodesy. Some high density alloys (8.6-9.3 g/dm3) have been studied and characterised for producing the LARES 2 passive satellite. The considered materials were Copper and Nickel based alloys that have been produced and characterised. Aim of this work was to analyse their fracture behaviour that is a requirement for materials to be used for space applications. Fracture tests have been carried out on several specimens and fracture surfaces have been analysed.
关键词： Lares 2,material selection,Copper alloys
更新于2025-09-12 10:27:22
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Particle distribution in transient plasmas generated by ns-laser ablation on ternary metallic alloys
摘要： Understanding the fundamental mechanisms behind industrial laser-based technologies represents one the cornerstones of the development and tailoring of new materials. With the thin-film deposition using laser ablation being one of the most important techniques for obtaining complex materials with controllable stoichiometry, there is a high request for both experimental and theoretical studies towards understanding the behavior of multi-component alloys under high-power laser irradiation. Here we investigate the laser ablation process on two ternary metallic alloys (Cu–Mn–Al and Fe–Mn–Si) by means of space-and time-resolved optical emission spectroscopy and fast camera imaging with the focus being on the spatial distribution of each composing element. Information regarding the kinetic and thermal energy of the ejected particles is extracted and discussed in the framework of an inner structuring of the laser-produced plasmas based on a mass and energy distribution. The hypothesis is then verified by implementing a fractal analysis to the multi-component plasmas. The theoretical fractal approach offers results in good agreement with the experimental data gives important insight in the inner dynamics of complex laser-produced plasmas.
关键词： Ternary metallic alloys,Optical emission spectroscopy,Fractal analysis,Fast camera imaging,Laser ablation
更新于2025-09-12 10:27:22
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Stiffness and hardness gradients obtained by laser surface melting of an aged β-Ti alloy
摘要： Components with variable stiffness have been attracting interest because of their potential for use in biomedical implants. Here, a β-titanium alloy aged under different conditions was subjected to laser surface melting (LSM). The high cooling rate typical of LSM avoided α-phase precipitation in the fusion zone (FZ) and heat-affected zone (HAZ) as the α precipitates were solid-solutioned into the β phase, producing a surface layer with full β phase over the aged substrate and reduced stiffness and hardness. The decrease in stiffness occurred independently of the aging condition used while the decrease in hardness was greater for the sample aged at the lower temperature as this had finer precipitates. A route involving aging at this lower temperature and LSM is proposed for use when a graded material combining a less rigid surface with the original core stiffness and strength is required, as in orthopedic implants.
关键词： Laser processing,Graded materials,Elastic modulus,Titanium alloys
更新于2025-09-12 10:27:22