Direct laser sintering of metal powders: Mechanism, kinetics and microstructural features
25 Jul 2006-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing (Elsevier)-Vol. 428, Iss: 1, pp 148-158
TL;DR: In this article, the densification and microstructural evolution during direct laser sintering of metal powders were studied, and it was found that when melting/solidification approach is the mechanism of sinter, the densifiers of metals powders (D ) can be expressed as an exponential function of laser specific energy input ( ψ ) as ln(1−− D )−= ǫ− Kψ.
Abstract: In the present work, the densification and microstructural evolution during direct laser sintering of metal powders were studied. Various ferrous powders including Fe, Fe–C, Fe–Cu, Fe–C–Cu–P, 316L stainless steel, and M2 high-speed steel were used. The empirical sintering rate data was related to the energy input of the laser beam according to the first order kinetics equation to establish a simple sintering model. The equation calculates the densification of metal powders during direct laser sintering process as a function of operating parameters including laser power, scan rate, layer thickness and scan line spacing. It was found that when melting/solidification approach is the mechanism of sintering, the densification of metals powders ( D ) can be expressed as an exponential function of laser specific energy input ( ψ ) as ln(1 − D ) = − Kψ . The coefficient K is designated as “densification coefficient”; a material dependent parameter that varies with chemical composition, powder particle size, and oxygen content of the powder material. The mechanism of particle bonding and microstructural features of the laser sintered powders are addressed.
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TL;DR: Additive manufacturing implies layer by layer shaping and consolidation of powder feedstock to arbitrary configurations, normally using a computer controlled laser as discussed by the authors, which is based on a novel materials incremental manufacturing philosophy.
Abstract: Unlike conventional materials removal methods, additive manufacturing (AM) is based on a novel materials incremental manufacturing philosophy. Additive manufacturing implies layer by layer shaping and consolidation of powder feedstock to arbitrary configurations, normally using a computer controlled laser. The current development focus of AM is to produce complex shaped functional metallic components, including metals, alloys and metal matrix composites (MMCs), to meet demanding requirements from aerospace, defence, automotive and biomedical industries. Laser sintering (LS), laser melting (LM) and laser metal deposition (LMD) are presently regarded as the three most versatile AM processes. Laser based AM processes generally have a complex non-equilibrium physical and chemical metallurgical nature, which is material and process dependent. The influence of material characteristics and processing conditions on metallurgical mechanisms and resultant microstructural and mechanical properties of AM proc...
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TL;DR: In this article, the state of the art in selective laser sintering/melting (SLS/SLM) processing of aluminium powders is reviewed from different perspectives, including powder metallurgy (P/M), pulsed electric current (PECS), and laser welding of aluminium alloys.
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Cites background from "Direct laser sintering of metal pow..."
...The variation of the densification (D) with the specific energy input (ね) for iron-based powders of varying chemical composition under the same processing conditions [119]....
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...Simchi [119] also explored the densification kinetics of SLS processed Fe, Fe –C, –Cu, Fe–C– Cu–P, 316L stainless steel, and M2 high -speed powders....
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TL;DR: A review of published data on the mechanical properties of additively manufactured metallic materials can be found in this paper, where the additive manufacturing techniques utilized to generate samples covered in this review include powder bed fusion (eBM, SLM, DMLS) and directed energy deposition (eBF3).
Abstract: This article reviews published data on the mechanical properties of additively manufactured metallic materials. The additive manufacturing techniques utilized to generate samples covered in this review include powder bed fusion (e.g., EBM, SLM, DMLS) and directed energy deposition (e.g., LENS, EBF3). Although only a limited number of metallic alloy systems are currently available for additive manufacturing (e.g., Ti-6Al-4V, TiAl, stainless steel, Inconel 625/718, and Al-Si-10Mg), the bulk of the published mechanical properties information has been generated on Ti-6Al-4V. However, summary tables for published mechanical properties and/or key figures are included for each of the alloys listed above, grouped by the additive technique used to generate the data. Published values for mechanical properties obtained from hardness, tension/compression, fracture toughness, fatigue crack growth, and high cycle fatigue are included for as-built, heat-treated, and/or HIP conditions, when available. The effects of test...
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TL;DR: A review on the latest advances in the 3D printing of ceramics and present the historical origins and evolution of each related technique is presented in this paper. And the main technical aspects, including feedstock properties, process control, post-treatments and energy source-material interactions, are also discussed.
Abstract: Along with extensive research on the three-dimensional (3D) printing of polymers and metals, 3D printing of ceramics is now the latest trend to come under the spotlight. The ability to fabricate ceramic components of arbitrarily complex shapes has been extremely challenging without 3D printing. This review focuses on the latest advances in the 3D printing of ceramics and presents the historical origins and evolution of each related technique. The main technical aspects, including feedstock properties, process control, post-treatments and energy source–material interactions, are also discussed. The technical challenges and advice about how to address these are presented. Comparisons are made between the techniques to facilitate the selection of the best ones in practical use. In addition, representative applications of the 3D printing of various types of ceramics are surveyed. Future directions are pointed out on the advancement on materials and forming mechanism for the fabrication of high-performance ceramic components.
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TL;DR: A detailed overview of the thermal/fluid properties inherent in the direct laser deposition (DLD) process can be found in this article, with a focus on the mechanical properties and microstructure of parts manufactured via DLD.
Abstract: Laser-based additive manufacturing (LBAM) processes can be utilized to generate functional parts (or prototypes) from the ground-up via layer-wise cladding – providing an opportunity to generate complex-shaped, functionally graded or custom-tailored parts that can be utilized for a variety of engineering applications. Directed Energy Deposition (DED), utilizes a concentrated heat source, which may be a laser or electron beam, with in situ delivery of powder- or wire-shaped material for subsequent melting to accomplish layer-by-layer part fabrication or single-to-multi layer cladding/repair. Direct Laser Deposition (DLD), a form of DED, has been investigated heavily in the last several years as it provides the potential to (i) rapidly prototype metallic parts, (ii) produce complex and customized parts, (iii) clad/repair precious metallic components and (iv) manufacture/repair in remote or logistically weak locations. DLD and Powder Bed Fusion-Laser (PBF-L) are two common LBAM processes for additive metal part fabrication and are currently demonstrating their ability to revolutionize the manufacturing industry; breaking barriers imposed via traditional, ‘subtractive’ metalworking processes. This article provides an overview of the major advancements, challenges and physical attributes related to DLD, and is one of two Parts focused specifically on DLD. Part I (this article) focuses on describing the thermal/fluidic phenomena during the powder-fed DLD process, while Part II focuses on the mechanical properties and microstructure of parts manufactured via DLD. In this current article, a selection of recent research efforts – including methodology, models and experimental results – will be provided in order to educate the reader of the thermal/fluidic processes that occur during DLD, as well as providing important background information relevant to DLD as a whole. The thermal/fluid phenomena inherent to DLD directly influence the solidification heat transfer which thus impacts the part's microstructure and associated thermo-mechanical properties. A thorough understanding of the thermal/fluid aspects inherent to DLD is vital for optimizing the DLD process and ensuring consistent, high-quality parts.
781 citations
References
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TL;DR: In this paper, a mixture of different types of particles (Fe, Ni, Cu and Fe3P) specially developed for selective laser sintering (SLS) is described.
1,342 citations
Book•
01 Jan 1985
TL;DR: The use of liquid phase sintering has received increased attention as part of the growth in particulate materials processing as mentioned in this paper, which is attributed to an increased concern over energy utilization, a desire to better control microstructure in engineermg materials, the need for 1mproved material economy, societal and economic pressures for higher productivity and quality, requirements for unique property combinations for high performance applica- tions, and a desire for net shape forming.
Abstract: In the past few years there has been rapid growth in the activities involving particulate materials because of recognized advantages in manufacturing. This growth is attributed to several factors; i) an increased concern over energy utilization, ii) a desire to better control microstructure in engineermg materials, iii) the need for 1mproved material economy, iv) societal and economic pressures for higher productivity and quality, v) requirements for unique property combinations for high performance applica- tions, and vi) a desire for net shape forming. Accordingly, liquid phase sintering has received increased attention as part of the growth in particulate materials processing. As a consequence, the commercial applications for liquid phase sintering are expanding rapidly. This active and expanding interest is not well served by available texts. For this reason I felt it was appropriate to write this book on liquid phase sintering. The technology of liquid phase sintering IS quite old and has been in use in the ceramics industry for many centuries. However, the general perception among materials and manufacturing engineers is that liquid phase sintering is still a novel technique. I believe the diverse technological appli- cations outlined in this book will dispel I such impressions. Liquid phase. sintering has great value in fabricating several unique materials to near net shapes and will continue to expand in applications as the fundamental attrib- utes are better appreciated. I am personally involved with several uses for liquid phase sintering.
1,034 citations
Book•
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01 Jan 2003
TL;DR: De naam zegt het al: rapid prototyping is het snel vervaardigen van tastbare prototypen, modellen en boorsjablonen, voorbeelden van dit proces zijn stereolithografie en 3D-printing.
Abstract: SamenvattingZonder software geen CAD/CAM en zonder CAD/CAM geen rapid prototyping. De naam zegt het al: rapid prototyping is het snel vervaardigen van tastbare prototypen, modellen en boorsjablonen. Voorbeelden van dit proces zijn stereolithografie en 3D-printing.
630 citations
25 Oct 2003-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this article, the effects of processing parameters such as laser power, scan rate, scan line spacing, thickness of layer, scanning geometry and sintering atmosphere were studied, and it was found that the sintered density increased sharply with increasing the specific energy input until a critical energy input had been reached.
Abstract: The densification behavior and the attendant microstructural features of iron powder processed by direct laser sintering were investigated. The effects of processing parameters such as laser power, scan rate, scan line spacing, thickness of layer, scanning geometry and sintering atmosphere were studied. A specific energy input (ψ) was defined using the “energy conservation” rule to explore the effects of the processing condition on the density and the attendant microstructure of laser sintered iron. It was found that the sintered density increased sharply with increasing the specific energy input until a critical energy input had been reached (ψ∼0.2 kJ mm−3). The microstructure consists of large pores (>0.5 mm) and elongated ferrite grains parallel to the building direction. The increase in the sintered density was followed with further increasing the specific energy, but at slower rate. Intensifying the energy input over 0.8 kJ mm−3 leads to the formation of horizontally elongated pores while the sintered density remains almost constant. The inter-agglomerates are fully dense and consist of elongated ferrite grains which are oriented parallel to the building direction. The iron powder was used as a model material so the outcomes are generic and can be applied to other material systems with congruent melting point or systems which melting/solidification approach is the mechanism feasible for the rapid bonding of metal powders in direct laser sintering.
335 citations
TL;DR: In this article, a numerical simulation of the heat flow equation has been performed and compared with experimentally obtained titanium plates, which allowed to obtain a process map of the sintering process.
332 citations