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1.
Direct laser sintering of a copper-based alloy for creating three-dimensional metal parts 总被引:12,自引:0,他引:12
Y. Tang H.T. Loh Y.S. Wong J.Y.H. Fuh L. Lu X. Wang 《Journal of Materials Processing Technology》2003,140(1-3):368-372
Direct laser sintering of metal, as one of the important developments in rapid prototyping technologies, is discussed in this paper. A special copper-based alloy is used for this rapid prototyping process. Experiments on the sintering conditions of this material had been conducted in a self-developed high temperature metal sintering machine. The mechanism of laser sintering for this kind of material was disclosed by SEM analysis of microstructures of sintered parts. The density, surface roughness and mechanical properties of the laser sintering parts due to variation of process parameters were measured and analysed. The effect of process parameters to the accuracy of sintered parts was also investigated. Thus, optimum parameters were obtained for direct laser sintering of three-dimensional metal parts. 相似文献
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Microstructural evolution during direct laser sintering of multi-component Cu-based metal powder 总被引:1,自引:0,他引:1
A multi-component Cu-based metal powder was chosen for direct laser sintering. The powder consists of a mixture of high-purity Cu powder, pre-alloyed CuSn and CuP powder. Liquid phase sintering with complete melting of the binder (CuSn) but non-melting of the cores of structural metal (Cu) proves to be a feasible mechanism for laser sintering of this powder system. The microstructural evolution of the sintered powder with variation of laser processing parameters was presented. High sintering activities and sound densification response were obtained by optimizing the laser powers and scan speeds. Using a high laser power accompanied by a high scan speed gives rise to baUing effect. At a high laser power with a slow scan speed the sintering mechanism may change into complete melting/solidification, which decreases the obtainable sintered density. The role of additive phosphorus in the laser sintering process is addressed. Phosphorus can act as a fluxing agent and has a preferential reaction with oxygen to form phosphatic slag, protecting the Cu particles from oxidation. The phosphatic slag shows a concentration along grain boundaries due to its light mass as well as the short thermal cycle of SLS. 相似文献
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Direct laser sintering of metal powder is a promising manufacturing process to produce rapid moulds (or rapid tooling) because complex three-dimensional (3-D) metal parts can be created directly from computer-aided design (CAD) data without machining or use of additional tooling. However, material and process are still the crucial issues that restrict its wider adoption although the technology has been introduced more than 7 years. This paper characterises a self-developed Cu-based metal powder used for direct laser sintering. The material system is Cu-based alloy metal powder, which consists of two metal powders: high-purity Cu powder and pre-alloyed SCuP metal powder. The scanning electron microscope (SEM), XRD and energy dispersive X-ray (EDX) analyses show that the bonding mechanism of this process is liquid-phase sintering. The pre-alloyed SCuP metal powder with lower melting point (645 °C) acts as the binder during laser sintering, while the Cu powder with higher melting point (1083 °C) acts as the structure. The element phosphorus in the powder can act as flux to protect the Cu oxidisation. A case study on fabricating the inserts of a mobile phone cover mould was also carried out. The inserts were created in ambient atmosphere at room temperature. The total sintering time is 40 h. Sixty five percent relative theoretical density and average surface roughness Ra 14–16 μm were achieved with negligible distortion and curling. Epoxy infiltration was employed as post-process to improve the density and the strength of the sintered tooling. The mould inserts were used to inject ABS-PC mobile phone cover after polishing. No defects were found after moulding of 500 components. 相似文献
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应用结合的选择性激光烧结和冷等静压技术快速制造金属零件。使用有限元方法预测零件的最终尺寸并降低成本;使用Drucker-Prager-Cap模型在ABAQUS软件中实现对选择性激光烧结零件的冷等静压过程的模拟。金属粉末的性质通过冷等静压实验测量。结果表明:橡胶包套和摩擦因数对零件的形状和尺寸影响很小;零件只有均匀收缩,没有明显的形状扭曲。实验与模拟结果符合得较好,这表明Drucker-Prager-Cap模型是模拟冷等静压过程的有效模型;通过模拟可以为选择性激光烧结零件的冷等静压成形过程提供有益的指导。 相似文献
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Electron beam sintering of metal powder 总被引:1,自引:0,他引:1
The laser is widely used in additive layer manufacturing for producing parts on the basis of polymer and metal powder. In
the metal area, the capacity of laser technologies is noticeably exhausted. The electron beam (eb) technology offers higher
power density and beam velocity and therefore seems more suitable for sintering high-tensile steel powder in an economic way.
In this paper, a comprehensive method is implemented to develop the eb sintering. In comparison to laser-based applications,
different physical effects occur and have to be controlled. Therefore, the paper focusses on those physical effects and the
measures, which have to be taken in order to achieve a reliable process. The result of this work is a prototype machine, in
which the eb is used for sintering high-tensile steel directly from CAD files to three-dimensional, non-porous parts. 相似文献
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Metallic powder reuse presents attractive economic and environmental advantages for direct metal laser sintering (DMLS). However, continuous recycling of powder raises concerns of powder quality and sintered part performance, and complicates process validation. Efforts to examine the mechanical response of parts built with reused feedstocks are increasingly common in the technical literature, but none have optimized process parameters in DMLS to control for changes in material properties. In this paper, titanium powder reuse was investigated with the objective of optimizing the additive manufacturing (AM) process for reuse. Virgin Ti-6Al-4V powder was cycled a total of eight times through conditions representative of industrial DMLS machines. A full 23-factorial design of experiments (DOE) approach was employed to identify how parameter settings affect mechanical behavior, and include reuse as a process variable. The independent factors (laser power, laser speed, and hatch distance) did not significantly affect mechanical properties; however, measurements of ductility were found to be influenced by some interaction between the factors. These results were attributed to the narrow operating envelope which was required for successfully sintered specimens. Density and chemistry measurements further demonstrated no significant change with respect to reuse. The findings suggest that titanium powder can be reused up to eight times without any noticeable loss in strength or ductility. 相似文献
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A powder metallurgy (PM) process to fabricate alumina parts through indirect selective laser sintering (SLS) of spherical alumina-polyamide composite powder is presented. The PM process includes powder production, SLS, debinding and furnace sintering. Three different strategies are investigated in order to improve the density of the final alumina parts: laser remelting, warm isostatic pressing (WIP), and different infiltration techniques which use alumina containing suspensions: pressureless infiltration and infiltration under pressure (i.e. squeeze infiltration). Furthermore, microstructural and geometrical changes which occur during the PM process are investigated. 相似文献
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The paper describes a new powder composition specially developed for selective laser sintering (SLS). The aim is to obtain a ferro powder that can be sintered without need for a (sacrificial) polymer binder and that results in quasi dense parts that do not need any post-processing like furnace sintering, infiltration or HIP. The powder is a mixture of different types of particles (Fe, Cu, Ni and Fe3P). The composition and mixture ratio are justified by using phase diagrams. The powder has been tested using an own developed Nd: YAG SLS machine. The influence of process parameters (laser power, scan velocity, scan spacing and scan strategy) and the microstructural characteristics have been investigated. Attention is devoted to the binding mechanism (liquid phase sintering, through melting) and to the quality of resulting parts (density, balling effect,…). 相似文献
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Kahtan S. Mohammed Azmi Rahmat Azizan Aziz 《Journal of Materials Processing Technology》2013,213(7):1088-1094
Green compacts of W–bronze were encapsulated in shells of bronze powder, placed in a ceramic mold and sintered in alumina tube furnace at 1150 °C. Throughout the sintering cooling stage the differential coefficient of thermal expansion ΔCTE of W–bronze was employed to induce an external compressive densification action. The process included simultaneous sintering, hot isostatic pressing (HIP) and infiltration act to enhance densification. By this technique, pilot sintered compacts of different W50–80 wt.%–pre-mix bronze of 97–99% theoretical density were produced. This process resulted in compacts of higher hardness, higher sintered density and better structure homogeneity as opposed to similar compacts densified by the conventional sintering process. The results showed a gain in hardness by 10–20% and in density by 5–15%. The impact of different cooling rates of 3, 4, 8 and 30 °C min?1 on sintered density, microstructure and densification mechanisms was examined and evaluated. Low cooling rates of 3 and 4 °C min?1 gave the best results. 相似文献
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《Intermetallics》2016
An innovative powder metallurgical process (Electro-Sinter-Forging – ESF) has been applied to a gas atomized Ni–Ti powder to avoid the typical drawbacks of the conventional industrial processing of this material: oxygen pick up, high processing temperature and slow cooling rate. At the same time, the ESF allows to overcome the low sintering activity of the Ni–Ti powders. Sintered materials, produced by using different processing conditions, are characterized and compared. Results concerning the thermal, structural, microstructural and mechanical analyses are reported and discussed. The density of the sintered samples increases by increasing the amount of applied energy and final pressure during the sintering process. The sample showing the highest density has a direct phase transformation on heating and cooling, with broad DSC peaks, and small thermal hysteresis; it is austenitic at room temperature, with a low amount of coarse (micrometric) precipitates, Ti4Ni2Ox nanometric precipitates and high hardness. The ESF sintering at highest energies induces a “band-type” microstructure with a preferential crystallographic orientation; the crystallographic texture of the sintered samples has been investigated through Electron Back Scattering Diffraction (EBSD) analysis and a fiber texture <100> has been evidenced. The ion release from the sintered samples has been investigated: it is comparable to commercial Ni–Ti alloys currently used and it is correlated to the sample porosity. The biocompatibility has been demonstrated towards fibroblasts. 相似文献
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DERSDEPENDENCEOFSINTERABILITYONSTATEOFAGGLOMERATIONOFULTRAFINEZrO_2,(Y_2O_3)POWDERS¥Ge,Rongde;Liu,Zhihong;Chen,Huiguang;Zhang,... 相似文献
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Jinglian Fan Tao LiuSong Zhu Yong Han 《International Journal of Refractory Metals and Hard Materials》2012,30(1):33-37
Ultrafine/Nanocrystalline W-Cu composite powders with various copper contents (30, 40 and 50 wt.%) have been synthesized by sol-spray drying and a subsequent hydrogen reduction process. The powders were consolidated by direct sintering at temperatures between 1150 and 1260 °C for 90 min. The powder characteristics and sintering behavior, as well as thermal conductivity of the sintered alloys were investigated. The results show that the synthesized powders exist in ultrafine composite particles containing numerous nanosized particles, and the composition distributed very homogeneously. As the copper contents increase, the grain size of the powders decreases. The subsequent sintered parts show nearly full density with the relative density more than 99% at the temperature of 1250 °C. The sintered parts have very fine tungsten grains embedded in a bulk matrix. With increased copper contents, the tungsten grain size decreases and the microstructural homogeneity of the sintered alloys improves further. The thermal conductivity properties, while a little lower than that of the theoretical value, depend on the copper contents. 相似文献
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IGNITING SHS BY LASER AND ITS APPLICATION TO SELECTIVE LASER SINTERING OF METALLIC POWDER MATERIAL 总被引:1,自引:0,他引:1
Y.S. Shi S.C. Chen X.L. Lu S.H. HuangState Key Laboratory of Plastic Forming Simulation Die & Mould Technology School of Material Science Engineering Huazhong University of Science Technology Wuhan China 《金属学报(英文版)》2004,17(5)
1.IntroductionSelective laser sintering (SLS) is one of typical rapid prototyping (RP) technology. SLS adopts the idea of a delamination manufacturing, which is not limited by complicated degree of part shape and not needs any frock & mould, to directly fabricate three dimension (3D) solid parts with powder materials. Theoretically, any powder materials, which can felt each other after they are heated, may be SLS materi-als. Range of SLS materials have covered with polymer powder, cerami… 相似文献
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Y.S.Shi S.C.Chen X.L.Lu S.H.Huang 《金属学报(英文版)》2004,17(5):694-704
How to directly fabricate metallic functional parts with selective laser sintering (SLS) process is a potential technique that scientists are researching. Existent problems during directly fabricating metal part by use of SIS are analyzed. For the sake of solving the problems, a new idea of adding self-propagating high-temperature synthesis (SHS) material into metallic powder material to form new type of SIS metallic powder material is put forward. This powder material can release controllable amount of heat during its interaction with the laser beam energy to reduce the requirement to laser power during directly sintering metallic part, to prolong the time of metallic liquid phase existing, and to improve the intensity and accuracy of SIS part. For this reason, SHS material‘s interaction with the CO2 laser beam energy is researched, which proves that CO2 laser beam energy may instantly ignite SHS reaction. On the basis of the above-mentioned researches, the effect of sintering the metal powder material mixing SHS material with CO2 laser is also researched,which shows: there is an optimal blending ratio of various material in the new metallic powder material. Under the optimal blending ratio and SIS process parameters, this new metallic powder material can indeed release amount of heat and SHS reaction may be controlled within the laser sintering. This research result makes it possible that the metallic part is directly sintered with small CO2 laser (less than 50W), which may greatly reduce the volume, cost and running expenditure of SIS machine, be propitious to application. 相似文献
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A. Manonukul N. Muenya F. Léaux S. Amaranan 《Journal of Materials Processing Technology》2010,210(3):529-535
Porous metal has a high strength-to-weight ratio and can be produced by various methods. Powder metallurgy using a powder space holder, which is one of the metal foam fabrication techniques, can produce complex parts with a well-controlled foam structure. This work employed the metal injection moulding method with the use of a powder space holder, which was PMMA. The volume fraction of PMMA was varied from 0% to 50% to replace the metal volume fraction, while the binder volume fraction was kept constant. The results show that when more PMMA is added, the mixture of metal powder, binder and PMMA has higher wettability and became less viscous and more difficult to mix effectively and to inject. In addition, there were two competing shrinkages during sintering, which were the shrinkage due to the consolidation of the powder during sintering, which was always present, and the shrinkage of the foam structure after the power spacer was removed, which was a function of the volume fraction of PMMA. All results can be divided into two regions, which are the first region (0–35% PMMA) and the second region (35–50% PMMA). In the first region, as the volume fraction of PMMA increased, the sintered density and mechanical properties decreased, and the porosity per area decreased. For the second region, the sintered density and mechanical properties improved and the porosity per area increased as more PMMA was added. The original shape of the parts could not be retained in the second region. Microstructural observations supported these findings. 相似文献