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Inconel625/316L functionally graded material using spectral diagnostics during laser additive manufacturing process
摘要： In this paper, the composition of Inconel625/316L functionally graded material during the additive manufacturing process was monitored on-line by laser-induced plasma optical emission spectroscopy. Several spectral lines are used to establish the quantitative relationship between relative intensity, relative intensity ratio, plasma temperature, and functional gradient material composition variation. It is shown that the change between relative strength and compositional content is similar to actual expectations. But, the relationship between the relative intensity with Inconel625 content is nonlinear. Cr-I/Ni-I relative intensity ratios almost linearly decrease with increasing Inconel625 content. The linear correlation coe?cient of the best ?tted curve was 0.943, and the maximum percentage error was 7.5%. The plasma temperature was obtained by the Boltzmann plot using ?ve neutral chrome lines between 330 and 380 nm. Plasma temperature almost linearly increases with increasing Inconel625 content in a range. The linear correlation coe?cient of the plasma temperature ?tted straight line was 0.93, and the maximum percentage error was 2.7%. The feasibility of composition monitoring of gradient materials by spectral information during the additive manufacturing process was veri?ed.
关键词： plasma temperature,spectral diagnosis,laser additive manufacturing,composition monitoring
更新于2025-11-28 14:24:20
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Laser additive manufacturing of Zn-2Al part for bone repair: Formability, microstructure and properties
摘要： Zinc (Zn) alloys are promising bone repair materials due to their inherent degradability, favorable mechanical property and biocompatibility. In this investigation, laser powder bed fusion (LPBF) known as a representative additive manufacturing technique was applied to fabricate Zn-2Al (wt.%) part for bone repair application. A low energy density (Ev) led to the formation of pores and resultant insufficient densification rate due to the high liquid viscosity within the molten pool. In contrast, a high Ev caused the evaporation of Zn powder and resultant failure of LPBF. With Ev increasing, the obtained grains and the precipitated lamellar eutectic structure contained η-Zn and α-Al phase became coarsened, which could be attributed to the enhanced heat accumulation and consequently decreased cooling rate. At optimized Ev of 114.28 J/mm3, fully dense Zn-2Al part with a densification rate of 98.3±1.4% was achieved, which exhibited an optimal hardness of 64.5±1.8 Hv, tensile strength of 192.2±5.4 MPa and a moderate corrosion rate of 0.14 mm/year. In addition, in vitro cell tests confirmed its good biocompability. This study indicated that LPBF processed Zn-2Al part was a potential material for bone repair.
关键词： Zn alloys,laser additive manufacturing,mechanical properties,degradation rate,biocompability
更新于2025-11-21 11:18:25
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Grain size evolution under different cooling rate in laser additive manufacturing of superalloy
摘要： The processing parameters in laser additive manufacturing have a crucial impact on solidification microstructure especially grain size, thus influencing the properties of the final products. In this paper, experiments were conducted to investigate the effects of processing parameters including scanning speed, laser power and powder feeding rate on grain size of the solidified track during laser metal deposition. A three-dimensional model considering heat transfer, phase change and Marangoni convection flow had also been developed to simulate the solidification parameters especially cooling rate (G × R) to illustrate the underlying mechanisms. The experimental and simulated results indicated that cooling rate increased and grain size decreased from 8.7 μm to 4.7 μm with the increase of scanning speed from 2 mm/s to 10 mm/s. Contrarily, cooling rate decreased and grain size increased with the increase of laser power and powder feeding rate. The numerical and experimental results provide the additive manufacturing process with the potential of microstructure control and performance optimization.
关键词： Grain size,Laser additive manufacturing,Superalloy,Solidification,Cooling rate
更新于2025-11-21 11:18:25
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Effect of laser shock processing on oxidation resistance of laser additive manufactured Ti6Al4V titanium alloy
摘要： The high-temperature oxidation resistance of laser additive manufactured (LAM) Ti6Al4V before and after laser shock processing (LSP) was investigated. The samples were oxidized at 400?800 °C for 1?50 h in air. The results revealed that the rate of weight gain of the Ti6Al4V fabricated through LAM decreased, and LSP had a positive effect on increasing the oxidation resistance. At an oxidation temperature of 700 °C, an aluminum-rich layer was observed in the cross-section before LSP. After LSP, the aluminum-rich layer changed to three layers. The aluminum-rich layer prevented the diffusion of oxygen, which improved the oxidation resistance of the Ti6Al4V.
关键词： Ti6Al4V titanium alloy,High-temperature oxidation resistance,Laser shock processing,Laser additive manufacturing
更新于2025-09-23 15:21:01
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The effects of laser peening on laser additive manufactured 316L steel
摘要： Laser peening has an extensive application in traditional manufacturing industry. However, in additive manufacturing, the initial stresses on the parts often reduce the effects of laser peening and make it hard to achieve a desirable residual stress distribution. In this investigation, the interaction of initial residual stress and laser peening-induced stress was studied through numerical simulation and experimental tests. A finite element model (FEM) model was built to predict the stress distribution on laser-deposited sample, and its changed state is affected by laser peening. The microstructure and mechanical properties were also characterized experimentally. The result turned out that the thermal-induced tensile residual stress in laser-deposited sample can affect the laser peening result in both horizontal and longitudinal directions. Some mechanical properties of the LAMed sample were changed after LSP treatment. The hardness on the surface and 1-mm depth have been increased by 7% and 22%, respectively, and the yield strength was increased by 16%, while there is no significant change in the tensile strength and elongation rate.
关键词： Finite element analysis,Laser peening,Laser additive manufacturing,Residual stress
更新于2025-09-23 15:21:01
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Molecular dynamics simulation of coalescence kinetics and neck growth in laser additive manufacturing of aluminum alloy nanoparticles
摘要： Laser additive manufacturing emerged as an advanced manufacturing process to fabricate components in a layered fashion by fusing the powder particles. This process is multifaceted and pivotal to understand the underlying physics of the coalescence of powder particles during the process, which impacts the structural and mechanical properties of the build component. In this study, a classical molecular dynamics (MD) model is developed for the coalescence of pre-alloyed aluminum alloy (AlSi10Mg) particles during the laser additive manufacturing process. The model is employed to investigate the neck growth and coalescence kinetics of different pairs of particle size with changing the laser energy density from 7 to 17 J/mm2. The simulation results reveal that the unevenly sized particles undergo complete coalescence as compared with even-sized particles, and the neck growth rate of AlSi10Mg particles increases with an increase in laser energy density. Based on the present investigation, it is established that the coalescence kinetics of the AlSi10Mg nanoparticles are governed by the surface and volume diffusion and the surface energy reduction during the joining of particles. This analysis will act as a guideline to design process parameters and quality control for the printing of new components.
关键词： Molecular dynamics,Laser additive manufacturing,Coalescence,Laser energy density,Powder bed fusion
更新于2025-09-23 15:21:01
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Dynamic Laser Absorptance Measured in a Geometrically Characterized Stainless-Steel Powder Layer
摘要： The relationship between real powder distributions and optical coupling is a critical building block for developing a deeper physical understanding of laser-additive manufacturing and for creating more reliable and accurate models for predictable manufacturing. Laser-light absorption by a metal powder is distinctly different from that of a solid material, as it is impacted by additional parameters, such as particle size, shape distribution, and packing. Here, we use x-ray computed tomography to experimentally determine these parameters in a thinly spread austenitic stainless-steel powder on a metal substrate, and we combine these results with optical absorptance measurements during a 1 ms stationary laser-light exposure to simulate the additive-manufacturing process. Within the thinly spread powder layer, the particle volume fraction changes continuously from near zero at the powder surface to a peak value of 0.72 at a depth of 235 μm, with the most rapid increase taking place in the first 100 μm. The relationship between this particle volume fraction gradient and optical absorptance is investigated using an analytical model, which shows that depth-averaged absorptance measurements can measure the predicted average value, but will fail to capture local effects that result from a changing powder density. The time-averaged absorptance remains at levels between 0.67 and 0.80 across a two orders of magnitude range in laser power, which is significantly higher than that observed in solid stainless-steel experiments. The dynamic behavior of the absorptance, however, reveals physical phenomena, including oxidation, melting, and vapor cavity (keyhole) formation, as well as quantifying the effect of these on the absorbed energy.
关键词： keyhole formation,laser-additive manufacturing,stainless-steel powder,x-ray computed tomography,optical coupling,optical absorptance,particle volume fraction
更新于2025-09-23 15:21:01
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Application of Atom Probe Tomography to Complex Microstructures of Laser Additively Manufactured Samples
摘要： Additive Manufacturing (AM) technologies have gained increasing interest across multiple industrial sectors ranging from biomedical to aerospace. AM is not only used for prototyping, but also for tooling as well as for final part production. The computer-controlled, layer-by-layer building up process allows for increased design freedom enabling to produce almost any shape. Additional benefits are potential resource efficiency, increased product customization and lightweight design. Two prominent metal-based laser AM (LAM) techniques are laser powder bed fusion (LPBF) and laser metal deposition (LMD). In LPBF, a focused laser beam is scanned over a bed filled with metal powder to locally melt and fuse the powder to produce fully dense metal parts. The next layer of powder is then distributed and the laser scans again. LMD is a nozzle-based AM process in which a focused laser beam creates a melt pool in the build’s surface. Metallic powder is then injected into the melt pool through a nozzle. The 3D part is built by moving the nozzle/laser assembly forward track by track and layer by layer. Material produced by LAM exhibits a unique thermal history: initially, the material is cooled rapidly from the liquid state in the meltpool. Subsequently, the material experiences a cyclic reheating, the so-called intrinsic heat treatment (IHT), as neighboring tracks and further layers are deposited during the LAM process. Consequences of this thermal history are very complex, sometimes hierarchical microstructures with inhomogeneities at scales ranging from nanometers up millimeters. Fully understanding and characterizing these microstructures is challenging and requires the combination of methods spanning a similar range: from light optical microscopy (LOM) to electron microscopy to atom probe tomography (APT). Here we present examples how APT can deliver valuable information on complex microstructures to better understand the IHT, rapid solidification as well as phase separation in different metallic alloys. Here I will discuss examples in steel, Al- and Ni-based superalloys, and high entropy alloys (HEA).
关键词： Laser Additive Manufacturing,Additive Manufacturing,Phase Separation,Microstructures,Atom Probe Tomography,Rapid Solidification,Intrinsic Heat Treatment
更新于2025-09-23 15:19:57
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In-process measurement of melt pool cross-sectional geometry and grain orientation in a laser directed energy deposition additive manufacturing process
摘要： Understanding the behaviour of melt pool during laser directed energy deposition (L-DED) is essential for the prediction and control of process quality. Previous effort was focused on the observation of melt pool surface characteristics. In this paper, a coaxial imaging system was employed to determine the melt pool cross sectional geometry and to predict solidified grain orientation during a high deposition rate L-DED process. The image processing procedure, deposition track cross-sectional profile prediction and the relationship between melt pool shape and melt pool dynamics, and grain growth orientation were investigated. Results show that sharp melt pool edges can be obtained so that melt pool width can be predicted with an accuracy of more than 95%. The estimation method of melt pool length has an accuracy of 90%. With the experimental melt pool width and depth data, the cross-sectional profiles of deposited track are predicted at an accuracy of 92% and a good match with experimental data is obtained. The melt pool formation is found to be able to allow the prediction of crystal growth directions during solidification.
关键词： Melt pool dimension,Laser additive manufacturing,Track geometry,Laser directed energy deposition,Grain growth
更新于2025-09-23 15:19:57
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Microstructure and properties of Tia??Zr congruent alloy fabricated by laser additive manufacturing
摘要： In the present work, Ti40Zr (atomic percent) congruent alloy, as well as four other Ti-Zr alloys near the congruent point, was fabricated using laser additive manufacturing (LAM) on pure titanium substrate. Comparative analyses of these alloys were performed based on microstructure, mechanical properties, tribological properties, corrosion resistance, and formability. The results show that the microstructure of the alloys develops sequentially from the Widmanst?tten structure to nearly full b -(TiZr) columnar crystals for 40 at.% Zr, to b -(TiZr) columnar crystals plus granular a -(TiZr) with the increase of Zr addition. The Ti60Zr40 congruent alloy with nearly full b -(TiZr) structure presents a novel combination of ductility, corrosion resistance, and formability, but it has a slightly lower hardness, less strength and poor tribological properties, compared with the other Ti-Zr alloys near the congruent point. Therefore, to develop the congruent alloy as a high strength LAM material through alloying is very significant.
关键词： Congruent Alloy,Laser additive manufacturing,Titanium alloy,Properties,Microstructure
更新于2025-09-23 15:19:57