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Journal ArticleDOI

Additive manufacturing of metallic components – Process, structure and properties

01 Mar 2018-Progress in Materials Science (Pergamon)-Vol. 92, pp 112-224

Abstract: Since its inception, significant progress has been made in understanding additive manufacturing (AM) processes and the structure and properties of the fabricated metallic components. Because the field is rapidly evolving, a periodic critical assessment of our understanding is useful and this paper seeks to address this need. It covers the emerging research on AM of metallic materials and provides a comprehensive overview of the physical processes and the underlying science of metallurgical structure and properties of the deposited parts. The uniqueness of this review includes substantive discussions on refractory alloys, precious metals and compositionally graded alloys, a succinct comparison of AM with welding and a critical examination of the printability of various engineering alloys based on experiments and theory. An assessment of the status of the field, the gaps in the scientific understanding and the research needs for the expansion of AM of metallic components are provided.
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01 Jan 2016-
TL;DR: The numerical heat transfer and fluid flow is universally compatible with any devices to read and is available in the authors' digital library an online access to it is set as public so you can get it instantly.
Abstract: Thank you for reading numerical heat transfer and fluid flow. Maybe you have knowledge that, people have search numerous times for their favorite books like this numerical heat transfer and fluid flow, but end up in infectious downloads. Rather than reading a good book with a cup of coffee in the afternoon, instead they cope with some malicious virus inside their computer. numerical heat transfer and fluid flow is available in our digital library an online access to it is set as public so you can get it instantly. Our books collection spans in multiple countries, allowing you to get the most less latency time to download any of our books like this one. Merely said, the numerical heat transfer and fluid flow is universally compatible with any devices to read.

1,193 citations

Journal ArticleDOI
David L. Bourell1, Jean-Pierre Kruth2, Ming C. Leu3, Gideon Levy  +3 moreInstitutions (6)
01 Jan 2017-CIRP Annals
Abstract: Critical to the selection requirements for additive manufacturing (AM) is the need for appropriate materials. Materials requirements for AM include the ability to produce the feedstock in a form amenable to the specific AM process, suitable processing of the material by AM, capability to be acceptably post-processed to enhance geometry and properties, and manifestation of necessary performance characteristics in service. As AM has matured, specific classes of material have become associated with specific AM processes and applications. This paper gathers this information for each of the seven categories of ISO/ASTM AM categories. Polymers, metals, ceramics and composites are considered. Microstructural features affecting AM part properties are listed. Service properties of AM parts are described, including physical, mechanical, optical and electrical properties. An additive manufacturability index is proposed.

399 citations

Journal ArticleDOI
Nesma T. Aboulkhair1, Marco Simonelli1, Luke Parry1, Ian Ashcroft1  +2 moreInstitutions (1)
Abstract: Metal Additive Manufacturing (AM) processes, such as selective laser melting (SLM), enable the fabrication of arbitrary 3D-structures with unprecedented degrees of freedom. Research is rapidly progressing in this field, with promising results opening up a range of possible applications across both scientific and industrial sectors. Many sectors are now benefiting from fabricating complex structures using AM technologies to achieve the objectives of light-weighting, increased functionality, and part number reduction, among others. AM also lends potential in fulfilling demands for reducing the cost and design-to-manufacture time. Aluminium alloys are of the main material systems receiving attention in SLM research, being favoured in many high-value applications. However, processing them is challenging due to the difficulties associated with laser-melting aluminium where parts suffer various defects. A number of studies in recent years have developed approaches to remedy them and reported successful SLM of various Al-alloys and have gone on to explore its potential application in advanced componentry. This paper reports on recent advancements in this area and highlights some key topics requiring attention for further progression. It aims to develop a comprehensive understanding of the interrelation between the various aspects of the subject, as this is essential to demonstrate credibility for industrial needs.

293 citations

Journal ArticleDOI
Abstract: Additive manufacturing technologies based on melting and solidification have considerable similarities with fusion-based welding technologies, either by electric arc or high-power beams. However, several concepts are being introduced in additive manufacturing which have been extensively used in multipass arc welding with filler material. Therefore, clarification of fundamental definitions is important to establish a common background between welding and additive manufacturing research communities. This paper aims to review these concepts, highlighting the distinctive characteristics of fusion welding that can be embraced by additive manufacturing, namely the nature of rapid thermal cycles associated to small size and localized heat sources, the non-equilibrium nature of rapid solidification and its effects on: internal defects formation, phase transformations, residual stresses and distortions. Concerning process optimization, distinct criteria are proposed based on geometric, energetic and thermal considerations, allowing to determine an upper bound limit for the optimum hatch distance during additive manufacturing. Finally, a unified equation to compute the energy density is proposed. This equation enables to compare works performed with distinct equipment and experimental conditions, covering the major process parameters: power, travel speed, heat source dimension, hatch distance, deposited layer thickness and material grain size.

208 citations

Cites background from "Additive manufacturing of metallic ..."

  • ...Schematic representation of the effect of temperature gradient and growth rate on the solidification microstructures (from [1])....


  • ...Several research efforts are ongoing, attempting to predict component characteristics that could accomplish process certification [1]....


Journal ArticleDOI
H Shipley1, Darren McDonnell1, M. Culleton1, R. Coull1  +3 moreInstitutions (1)
Abstract: Selective Laser Melting (SLM) is an additive manufacturing (AM) technique which has been heavily investigated for the processing of Ti-6Al-4V (Ti64) which is used in the biomedical, aerospace and other industries. To date the SLM processing of this material has been inhibited by the requirement of post processes due to three primary challenges of martensitic microstructures, undesired porosity and residual stresses which are present in the as-built state. This work identifies the state of the art in process optimisation which is being used to confront these challenges in the as-built state with a view to removing the reliance on post processing. Regarding process optimisation, maximising part density is the primary goal due to the negative influence of pores on fracture and fatigue properties. To accomplish this, a high energy input is required which results in high cooling rates during processing. It is these cooling rates which are instrumental in the microstructural evolution and residual stress production. Accordingly novel methods have been proposed which aim to maintain the necessary high level of energy input but control the cooling rates to tailor the microstructure and reduce residual stresses. Research gaps have been identified pertaining to all three of these challenges when considering mechanical properties of as-built components. Thus in its current state post processes remain critical, however promising techniques in early stage development provide encouragement going forward.

202 citations

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01 Jan 1980-
Abstract: This book focuses on heat and mass transfer, fluid flow, chemical reaction, and other related processes that occur in engineering equipment, the natural environment, and living organisms. Using simple algebra and elementary calculus, the author develops numerical methods for predicting these processes mainly based on physical considerations. Through this approach, readers will develop a deeper understanding of the underlying physical aspects of heat transfer and fluid flow as well as improve their ability to analyze and interpret computed results.

21,638 citations

Journal ArticleDOI
William E. Frazier1Institutions (1)
Abstract: This paper reviews the state-of-the-art of an important, rapidly emerging, manufacturing technology that is alternatively called additive manufacturing (AM), direct digital manufacturing, free form fabrication, or 3D printing, etc. A broad contextual overview of metallic AM is provided. AM has the potential to revolutionize the global parts manufacturing and logistics landscape. It enables distributed manufacturing and the productions of parts-on-demand while offering the potential to reduce cost, energy consumption, and carbon footprint. This paper explores the material science, processes, and business consideration associated with achieving these performance gains. It is concluded that a paradigm shift is required in order to fully exploit AM potential.

2,960 citations

"Additive manufacturing of metallic ..." refers background in this paper

  • ...Wire and metallic sheet based AM processes are fast but lack dimensional accuracy and result in defects and poor surface finish especially for parts with complex shapes [13,14]....


01 Jan 1990-
Abstract: The most comprehensive and authoritative single-volume reference on nonferrous metals and alloys. Provides detailed information on major alloy groups, with particular emphasis on aluminum, titanium, copper, and magnesium. New topics include recycling, superconductors, metal-matrix composites, and intermetallics. Contents include: Specific Metals and Alloys, Special-Purpose Alloys, Superconducting Materials, Pure Metals, Recycling, and Toxicity of Metals. This is the second of two volumes in the ASM Handbook that present information on compositions, properties, selection, and applications of metals and alloys. In Volume 1, irons, steels, and superalloys are described. In the volume, nonferrous alloys, superconducting materials, pure metals, and materials developed for use in special applications are reviewed. These companion volumes document some of the more important changes and developments that have taken place in materials science during recent decadesuchanges that undoubtedly will continue to impact materials engineering into the 21st century.

2,480 citations

Additional excerpts

  • ...5 145 (min) Invar 36 Cast - typical 265 483 44 – [497,685] Annealed - typical 260 470 37 131 ....


Journal ArticleDOI
Abstract: A mathematical model for weld heat sources based on a Gaussian distribution of power density in space is presented. In particular a double ellipsoidal geometry is proposed so that the size and shape of the heat source can be easily changed to model both the shallow penetration arc welding processes and the deeper penetration laser and electron beam processes. In addition, it has the versatility and flexibility to handle non-axisymmetric cases such as strip electrodes or dissimilar metal joining. Previous models assumed circular or spherical symmetry. The computations are performed with ASGARD, a nonlinear transient finite element (FEM) heat flow program developed for the thermal stress analysis of welds.* Computed temperature distributions for submerged arc welds in thick workpieces are compared to the measured values reported by Christensen1 and the FEM calculated values (surface heat source model) of Krutz and Segerlind.2 In addition the computed thermal history of deep penetration electron beam welds are compared to measured values reported by Chong.3 The agreement between the computed and measured values is shown to be excellent.

2,063 citations

"Additive manufacturing of metallic ..." refers background in this paper

  • ...For example, idealized two-dimensional calculations have been undertaken [87,88], and in some instances, heat sources have been simplified as a line source or double ellipsoid heat source [89] that are contrary to the measured power density distribution data for heat sources....


Journal ArticleDOI
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...

1,900 citations

"Additive manufacturing of metallic ..." refers background in this paper

  • ...Lower linear heat inputs result in smaller melt pools, higher thermal gradients, and therefore fast cooling rates and fine microstructures, leading to higher yield and ultimate tensile strengths compared to components made with higher linear heat inputs [7,357,472,474]....


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