The Experts below are selected from a list of 402 Experts worldwide ranked by ideXlab platform
Christian Coddet - One of the best experts on this subject based on the ideXlab platform.
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Effects of processing parameters on properties of selective laser melting mg 9 al powder mixture
Materials & Design, 2012Co-Authors: Han Lin Liao, Christian CoddetAbstract:Abstract In the present study, selective laser melting (SLM) was used to sinter a powder mixture of Mg–9%Al. Both densification mechanism and microstructure evolution of laser sintered powder mixture were established. The Effect of laser processing parameter on Mg–9%Al powder using SLM was also investigated. It can be found that a maximum relative density was 82% with preferable process parameters of v = 0.02 m/s, P = 15 W. An overlapped structure can be obtained when decreasing the laser energy density due to an incomplete melt. On the other hand, a severe particulate agglomeration appeared as the increase of the laser energy due to a Balling Effect. A critical scanning speed of 0.02 m/s can ensure that the particulates were well melted and not evaporated during the experiment. Moreover, the Mg and Al elements were dispersed uniformly in the samples. The microstructure and composition phase were studied through scanning electron microscopy (SEM) and X-ray elemental mapping (XRD) respectively.
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Effects of processing parameters on properties of selective laser melting mg 9 al powder mixture
Materials & Design, 2012Co-Authors: Baicheng Zhang, Han Lin Liao, Christian CoddetAbstract:Abstract In the present study, selective laser melting (SLM) was used to sinter a powder mixture of Mg–9%Al. Both densification mechanism and microstructure evolution of laser sintered powder mixture were established. The Effect of laser processing parameter on Mg–9%Al powder using SLM was also investigated. It can be found that a maximum relative density was 82% with preferable process parameters of v = 0.02 m/s, P = 15 W. An overlapped structure can be obtained when decreasing the laser energy density due to an incomplete melt. On the other hand, a severe particulate agglomeration appeared as the increase of the laser energy due to a Balling Effect. A critical scanning speed of 0.02 m/s can ensure that the particulates were well melted and not evaporated during the experiment. Moreover, the Mg and Al elements were dispersed uniformly in the samples. The microstructure and composition phase were studied through scanning electron microscopy (SEM) and X-ray elemental mapping (XRD) respectively.
Han Lin Liao - One of the best experts on this subject based on the ideXlab platform.
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Effects of processing parameters on properties of selective laser melting mg 9 al powder mixture
Materials & Design, 2012Co-Authors: Han Lin Liao, Christian CoddetAbstract:Abstract In the present study, selective laser melting (SLM) was used to sinter a powder mixture of Mg–9%Al. Both densification mechanism and microstructure evolution of laser sintered powder mixture were established. The Effect of laser processing parameter on Mg–9%Al powder using SLM was also investigated. It can be found that a maximum relative density was 82% with preferable process parameters of v = 0.02 m/s, P = 15 W. An overlapped structure can be obtained when decreasing the laser energy density due to an incomplete melt. On the other hand, a severe particulate agglomeration appeared as the increase of the laser energy due to a Balling Effect. A critical scanning speed of 0.02 m/s can ensure that the particulates were well melted and not evaporated during the experiment. Moreover, the Mg and Al elements were dispersed uniformly in the samples. The microstructure and composition phase were studied through scanning electron microscopy (SEM) and X-ray elemental mapping (XRD) respectively.
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Effects of processing parameters on properties of selective laser melting mg 9 al powder mixture
Materials & Design, 2012Co-Authors: Baicheng Zhang, Han Lin Liao, Christian CoddetAbstract:Abstract In the present study, selective laser melting (SLM) was used to sinter a powder mixture of Mg–9%Al. Both densification mechanism and microstructure evolution of laser sintered powder mixture were established. The Effect of laser processing parameter on Mg–9%Al powder using SLM was also investigated. It can be found that a maximum relative density was 82% with preferable process parameters of v = 0.02 m/s, P = 15 W. An overlapped structure can be obtained when decreasing the laser energy density due to an incomplete melt. On the other hand, a severe particulate agglomeration appeared as the increase of the laser energy due to a Balling Effect. A critical scanning speed of 0.02 m/s can ensure that the particulates were well melted and not evaporated during the experiment. Moreover, the Mg and Al elements were dispersed uniformly in the samples. The microstructure and composition phase were studied through scanning electron microscopy (SEM) and X-ray elemental mapping (XRD) respectively.
Yifu Shen - One of the best experts on this subject based on the ideXlab platform.
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Balling phenomena in direct laser sintering of stainless steel powder metallurgical mechanisms and control methods
Materials & Design, 2009Co-Authors: Yifu ShenAbstract:Abstract Balling Effect, as an unfavorable defect associated with direct metal laser sintering (DMLS), is a complex physical metallurgical process. In this work, two kinds of Balling phenomena during DMLS of 316L stainless steel powder were investigated and the metallurgical mechanisms of Balling were elucidated. It was found that using a low laser power gave rise to the first kind of Balling characterized by highly coarsened balls possessing an interrupted dendritic structure in the surface layer of balls. A limited amount of liquid formation and a low undercooling degree of the melt due to a low laser input was responsible for its initiation. The second kind of Balling featured by a large amount of micrometer-scaled (∼10 μm) balls on laser sintered surface occurred at a high scan speed. Its formation was ascribed to laser-induced melt splashes caused by a high capillary instability of the melt. Feasible control methods were proposed to alleviate Balling phenomena. It showed that increasing the volumetric density of energy input, which was realized by increasing laser power, lowering scan speed, or decreasing powder layer thickness, decreased the tendency of Balling. The addition of a trace amount of deoxidant (H 3 BO 3 and KBF 4 ) in the powder yielded a smooth laser sintered surface free of Balling.
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influence of cu liquid content on densification and microstructure of direct laser sintered submicron w cu micron cu powder mixture
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2008Co-Authors: Yifu ShenAbstract:Abstract The direct metal laser sintering (DMLS) was used to consolidate a composite powder system consisting of submicron W–Cu powder and micron Cu powder. The influence of Cu-liquid content on densification response of direct laser sintered W–Cu components was investigated. It was found that a proper increase of Cu elemental fraction to 60 wt.% yielded a high densification of 94.8% theoretical density, due to a favorable viscosity of liquid–solid mixture and the resultant sufficient rearrangement of W particles. However, a further increase in Cu content deteriorated laser sintered density, because of “Balling” Effect. The Effect of Cu-liquid content on microstructural features of laser-processed components was also studied. It showed that at a suitable Cu elemental content of 60 wt.%, a series of regularly shaped W-rim/Cu-core structures were formed after laser sintering. The metallurgical mechanisms for the formation of such a novel structure were proposed. It shows that the combined action of the thermal Marangoni flow and the solutal one, which are induced by temperature gradient and concentration differences at solid-liquid interfaces, accounts for the formation of the W-rim. The “particle pushing” Effect during rapid solidification of Cu melt prevents the W-rim from merging and, thus, remains the Cu-core after solidification.
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Effects of dispersion technique and component ratio on densification and microstructure of multi component cu based metal powder in direct laser sintering
Journal of Materials Processing Technology, 2007Co-Authors: Dongdong Gu, Yifu ShenAbstract:Abstract A multi-component Cu-based metal powder, which consisted of a mixture of Cu, CuSn, and CuP, was developed for direct metal laser sintering (DMLS). The Effects of powder characteristics such as particle shape, particle size and its distribution, and dispersion uniformity on the sintering behavior were studied. It is found that using a homogeneous powder mixture produced by ball mixing coarse and fine powders with a broad particle size distribution could increase the original density of the loose powder and, thus, the densification and microstructural homogeneity of the laser sintered powder. The influence of the binder (CuSn) content on the densification and the resultant microstructures of the laser sintered samples were also investigated. It shows that with increasing the amount of the binder, the microstructure became denser. However, at a high content larger than 50 wt.%, the densification showed a decrease, because of the “Balling” Effect.
Baicheng Zhang - One of the best experts on this subject based on the ideXlab platform.
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Effects of processing parameters on properties of selective laser melting mg 9 al powder mixture
Materials & Design, 2012Co-Authors: Baicheng Zhang, Han Lin Liao, Christian CoddetAbstract:Abstract In the present study, selective laser melting (SLM) was used to sinter a powder mixture of Mg–9%Al. Both densification mechanism and microstructure evolution of laser sintered powder mixture were established. The Effect of laser processing parameter on Mg–9%Al powder using SLM was also investigated. It can be found that a maximum relative density was 82% with preferable process parameters of v = 0.02 m/s, P = 15 W. An overlapped structure can be obtained when decreasing the laser energy density due to an incomplete melt. On the other hand, a severe particulate agglomeration appeared as the increase of the laser energy due to a Balling Effect. A critical scanning speed of 0.02 m/s can ensure that the particulates were well melted and not evaporated during the experiment. Moreover, the Mg and Al elements were dispersed uniformly in the samples. The microstructure and composition phase were studied through scanning electron microscopy (SEM) and X-ray elemental mapping (XRD) respectively.
Andrey V. Gusarov - One of the best experts on this subject based on the ideXlab platform.
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Optical diagnostics of selective laser melting and monitoring of single-track formation
MATEC Web of Conferences, 2017Co-Authors: Andrey V. Gusarov, Dmitriy V. Kotoban, Ivan ZhirnovAbstract:The article presents the optical diagnostics results of the selective laser melting process of single-track production. The track defects detection (such as Balling Effect, powder free zone formation, sparking) was shown, as well as the visualization of the independent particles consolidation in a solid track. The metal evaporation and the formation of the melt pool specific gas dynamic conditions were considered as important physical phenomena. The velocities of the particle emission from the melt pool, the rate of their involvement, and the velocity of the gas flow were estimated. The results make it possible to evaluate the kinetics of mass transfer under selective laser melting process. The surface thermal field of the laser-irradiated zone strongly influences the material qualitative characteristics after selective laser melting. The results becomes the basis for the development of optical monitoring and diagnostic systems for laser additive manufacturing processes based on the melt pool temperature online controlling.
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Model of Radiation and Heat Transfer in Laser-Powder Interaction Zone at Selective Laser Melting
Journal of Heat Transfer, 2009Co-Authors: Andrey V. Gusarov, Ph BertrandAbstract:A model for coupled radiation transfer and thermal diffusion is proposed, which provides a local temperature field. Single-line scanning of a laser beam over a thin layer of metallic powder placed on a dense substrate of the same material is studied. Both the laser beam diameter and the layer thickness are about 50 m. The typical scanning velocity is in the range of 10–20 cm/s. An Effective volumetric heat source is estimated from laser radiation scattering and absorption in a powder layer. A strong difference in thermal conductivity between the powder bed and dense material is taken into account. The above conditions correspond to the technology of selective laser melting that is applied to build objects of complicated shape from metallic powder. Complete remelting of the powder in the scanned zone and its good adhesion to the substrate ensure fabrication of functional parts with mechanical properties close to the ones of the wrought material. Experiments with single-line melting indicate that an interval of scanning velocities exists, where the remelted tracks are uniform. The tracks become “broken” if the scanning velocity is outside this interval. This is extremely undesirable and referred to as the “Balling” Effect. The size and the shape of the melt pool and the surface of the metallurgical contact of the remelted material to the substrate are analyzed in relation to the scanning velocity. The modeling results are compared with experimental observation of laser tracks. The experimentally found Balling Effect at scanning velocities above 20 cm/ s can be explained by the Plateau–Rayleigh capillary instability of the melt pool. Two factors destabilize the process with increasing the scanning velocity: increasing the length-to-width ratio of the melt pool and decreasing the width of its contact with the substrate.
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heat transfer modelling and stability analysis of selective laser melting
Applied Surface Science, 2007Co-Authors: Andrey V. Gusarov, Ph Bertrand, I SmurovAbstract:Abstract The process of direct manufacturing by selective laser melting basically consists of laser beam scanning over a thin powder layer deposited on a dense substrate. Complete remelting of the powder in the scanned zone and its good adhesion to the substrate ensure obtaining functional parts with improved mechanical properties. Experiments with single-line scanning indicate, that an interval of scanning velocities exists where the remelted tracks are uniform. The tracks become broken if the scanning velocity is outside this interval. This is extremely undesirable and referred to as the “Balling” Effect. A numerical model of coupled radiation and heat transfer is proposed to analyse the observed instability. The “Balling” Effect at high scanning velocities (above ∼20 cm/s for the present conditions) can be explained by the Plateau–Rayleigh capillary instability of the melt pool. Two factors stabilize the process with decreasing the scanning velocity: reducing the length-to-width ratio of the melt pool and increasing the width of its contact with the substrate.
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mechanisms of selective laser sintering and heat transfer in ti powder
Rapid Prototyping Journal, 2003Co-Authors: N K Tolochko, Andrey V. Gusarov, Maxim K Arshinov, V I Titov, Tahar Laoui, Ludo FroyenAbstract:Coupled metallographic examination and heat transfer numerical simulation are applied to reveal the laser sintering mechanisms of Ti powder of 63‐315 μm particle diameter. A Nd:YAG laser beam with a diameter of 2.7‐5.3 mm and a power of 10‐100 W is focused on a bed of loose Ti powder for 10 s in vacuum. The numerical simulation indicates that a nearly hemispherical temperature front propagates from the laser spot. In the region of α‐Ti just behind the front, heat transfer is governed by thermal radiation. The Balling Effect, formation of melt droplets, is not observed because the temperature increases gradually and the melt appears inside initially sintered powder which resists the surface tension of the melt.
