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Effects of laser scanning strategies on selective laser melting of pure tungsten
摘要： Three types of scanning strategies, including the chessboard scanning strategy, the zigzag scanning strategy and the remelting scanning strategy, were conducted to study the effects of scanning strategies on surface morphology, microstructure, mechanical properties and the grain orientation of selective laser melted pure tungsten. The results showed that the pores and cracks were main defects in SLM-processed tungsten parts. The pores could be eliminated using the remelting scanning strategy. However, the cracks seemed to be inevitable regardless of the applied scanning strategies. The microstructures of SLM-processed tungsten were columnar grains and showed strong epitaxial growth along the building direction. A compressive strength of 923 MPa with an elongation of 7.7% was obtained when the zigzag scanning strategy was applied, which was the highest among the three scanning strategies. By changing the scanning strategies, the texture of SLM-processed tungsten in the direction of processing could be changed.
关键词： microstructure,texture,scanning strategy,compressive strength,pure tungsten,selective laser melting
更新于2025-09-23 15:21:01
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Effect of Scanning Strategy During Selective Laser Melting on Surface Topography, Porosity, and Microstructure of Additively Manufactured Ti-6Al-4V
摘要： The effect of the scanning strategy during selective laser melting (SLM) of Ti-6Al-4V was investigated. An optimized cellular scan strategy (island scan modeled) was compared to a simple cellular scan strategy (island scan stripes) and a simple antiparallel line scanning strategy (line scan). Surface texture was investigated by optical three-dimensional (3D) surface measurements, which when combined with light optical microscopy (LOM), revealed deflections caused by the thermal stresses during the build process. Elevated edges caused by the edge-effect dominate the surface texture of all investigated specimens. The scanning strategy determines the surface texture, and the lowest surface roughness was obtained by the line scan strategy. Porosity was investigated with X-ray computed tomography-imaging. Mainly spherical porosity was observed for the line scan and island scan modeled specimens, while the island scan stripes strategy showed more lack-of-fusion defects and a higher total porosity amount. Microstructure was investigated with LOM and scanning electron microscopy (SEM). The microstructure in Ti-6Al-4V was largely martensitic α’ and prior β grains. The morphology is different for the various scan strategies, and decomposition of α’ into lamellar α/β was observed in the bottom part of the island scan specimen. Accordingly, the hardness decreased in the decomposed part of the specimen.
关键词： scanning strategy,porosity,surface topography,selective laser melting,powder bed fusion,microstructure,SLM,Ti-6Al-4V
更新于2025-09-23 15:21:01
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Experimental study on direct fabrication of micro channel on fused silica by picosecond laser
摘要： Ultrafast laser ablation, known for its high precision and the depressed thermal influence during processing, is fevered in micro channel fabrication on the glass bulk. In present work, a micro channel structure fabricated on fused silica bulk by a picosecond pulsed laser is parametrically investigated with different processing environments, scanning velocities, pulse energies, hatch distances and repetitive scans. The best processing parameters are determined through the material remove rate and the bottom surface roughness of the channel. Moreover, the fabrication defect attributed to the heat accumulation effect is analyzed by Raman spectrum. A scanning strategy is put forward to compensate the asymmetry in the cross section of the micro channels.
关键词： Heat accumulation,Surface roughness,Scanning strategy,Micro channel,Picosecond laser
更新于2025-09-23 15:21:01
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Numerical Study on Thermodynamic Behavior during Selective Laser Melting of 24CrNiMo Alloy Steel
摘要： In this paper, a multi-layer and multi-track ?nite element model of 24CrNiMo alloy steel by selective laser melting (SLM) is established by using the ABAQUS software. The distribution and evolution of temperature ?eld and stress ?eld and the in?uence of process parameters on them are systematically studied. The results show that the peak temperature increases from 2153 C and the residual stress increases from 335 MPa to 364 MPa with increasing laser power from 200 W to 300 W; the peak temperature decreases from 2905 C and the residual stress increases from 327 MPa to 363 MPa with increasing scanning speed from 150 mm/s to 250 mm/s; the peak C and the residual stress decreases from 354 MPa to 300 temperature increases from 2621 MPa with increasing preheating temperature from 25 C. Far away from scanning area, far away from starting point, and the adjacent areas with vertical scanning direction, resulting in a uniform temperature distribution, help to reduce the residual stress. Due to the remelting e?ect, the interlayer scanning angle changing helps to release the residual stress of the former layer causing a smaller residual stress after redistribution.
关键词： substrate preheating,?nite element analysis,thermodynamic behavior,selective laser melting,scanning strategy,24CrNiMo alloy steel
更新于2025-09-16 10:30:52
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Influence of Process Parameters and Deposition Strategy on Laser Metal Deposition of 316L Powder
摘要： In blown powder additive manufacturing technologies the geometrical stability of the built parts is more complex with respect to more conventional powder bed processes. Because of this reason, in order to select the most suitable building parameters, it is important to investigate the shape and the properties of the single metal bead formation and the effect that a scan track has on the nearby ones. In the present study, a methodology to identify an appropriate laser metal deposition process window was introduced, and the effect of the building parameters on the geometry of circular steel samples was investigated. The effect of the scanning strategy on the deposited part was also investigated. This work draws the attention to the importance of the obtainment of the most suitable melt pool shape, demonstrating that the laser power and the scanning strategy have a strong influence not only on the shape but also on the mechanical properties of the final component.
关键词： steel,additive manufacturing,melt pool,overlap,scanning strategy,directed energy deposition,AISI 316L
更新于2025-09-16 10:30:52
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Operando X-ray diffraction during laser 3D printing
摘要： Laser based additive manufacturing allows to build a designed shape layer-by-layer, offering versatility and flexibility to many metallurgical sectors. The fast cooling rates and repeated heat cycles depending on the laser and scanning parameters are not easily measurable with conventional methods. Thus, advanced predictive computational simulations, required to reduce trial and error lead time, are difficult to validate. A newly developed in operando X-ray diffraction device implemented at a synchrotron beamline, taking advantage of the high brilliance and the fast detectors available, brings the missing link with numerical methods. By performing operando experiments on Ti-6Al-4V with different printing parameters, the temporal evolution of the low and high temperature phases are followed, the heating and cooling rates are measured for the powder and the solid material; and the formation of residual stresses in the b phase is demonstrated. Moreover it is shown that the parameter that has the largest influence on the evolving microstructure is the scanning strategy, introducing a size effect related to the scanning length.
关键词： microstructure evolution,operando X-ray diffraction,scanning strategy,Laser based additive manufacturing,Ti-6Al-4V
更新于2025-09-12 10:27:22
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The effect of different scanning strategies on microstructural evolution to 24CrNiMo alloy steel during direct laser deposition
摘要： 24CrNiMo alloy steel is a low-alloy high strength steel and was used to fabricate engine components and brake discs. In the current study, Direct Laser Deposition (DLD) was used to additively manufacture 24CrNiMo alloy steel samples with high strength and ductility. The microstructural evolution, texture and mechanical properties of deposited samples can be affected by changing inter-layer time intervals and scanning strategy between deposited layers. The granular bainite (GB) and lath martensite (LM) inside deposited samples were obtained by inter-layer successive deposition and 2-minute intervals deposition, respectively, because of the different cooling rates of different inter-layer time intervals. The occurrence of 2-minute intervals between cladding layers leads to higher cooling rates, resulting in finer grain size. In addition, the relatively strong textures could be transformed into the weak ones since the columnar dendrites were fragmented by the different heat transfer directions resulting from a scanning strategy of 90°-rotation between cladding layers. Less inclusions and un-melted powders inside deposited samples were obtained when a scanning strategy of 90°-rotation between deposited layers was applied. The experimental results indicate that a deposited sample with excellent tensile properties and microhardness was fabricated by an optimized laser scanning strategy. The optimized scanning strategy mainly include inter-layer 2-minute intervals and 90°-rotation between deposited layers. Deposited samples fabricated by the optimized scanning strategy have comparable tensile strength and ductility to those of other forged low-alloy high strength steel. Therefore, this optimized laser scanning strategy can be applied to manufacture low-alloy steel with high tensile properties.
关键词： microstructural evolution,scanning strategy,direct laser deposition,mechanical properties,24CrNiMo alloy steel
更新于2025-09-11 14:15:04