Metal Additive Manufacturing: A Review
08 Apr 2014-Journal of Materials Engineering and Performance (Springer US)-Vol. 23, Iss: 6, pp 1917-1928
TL;DR: The state-of-the-art of additive manufacturing (AM) can be classified into three categories: direct digital manufacturing, free-form fabrication, or 3D printing as discussed by the authors.
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.
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TL;DR: In this paper, the recent progress on Ti6Al4V fabricated by three mostly developed additive manufacturing techniques-directed energy deposition (DED), selective laser melting (SLM) and electron beam melting (EBM)-is thoroughly investigated and compared.
1,248 citations
Cites methods from "Metal Additive Manufacturing: A Rev..."
...With respect to the fabrication of dense metallic structures, powder-based AM techniques such as DED, SLM and EBM are mostly used [22,23,26]....
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TL;DR: Additive manufacturing (AM) is fundamentally different from traditional formative or subtractive manufacturing in that it is the closest to the bottom-up manufacturing where a structure can be built into its designed shape using a "layer-by-layer" approach rather than casting or forming by technologies such as forging or machining as discussed by the authors.
1,124 citations
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...
1,093 citations
Cites background or methods from "Metal Additive Manufacturing: A Rev..."
...The recent reviews of the metal AM processes by Frazier (2) and Dutta & Froes (3) highlight some of the differences between the various processes....
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...ADDITIVELY MANUFACTURED ALLOY SYSTEMS As indicated in previous reviews (2, 3), at present there is only a limited number of alloy systems for which mechanical properties are published....
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...INTRODUCTION A number of metal additive manufacturing (AM) processes are currently available (1), depending on the heat source (2, 3), such as electron beam (2–7), laser, or arc (2, 3, 8, 9), and on how the raw material is supplied....
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...Frazier WE....
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TL;DR: In this article, the benefits of non-destructive testing, online monitoring and in situ machining are discussed, and strategies on how to manage residual stress, improve mechanical properties and eliminate defects such as porosity are suggested.
Abstract: Depositing large components (>10 kg) in titanium, aluminium, steel and other metals is possible using Wire + Arc Additive Manufacturing. This technology adopts arc welding tools and wire as feedstock for additive manufacturing purposes. High deposition rates, low material and equipment costs, and good structural integrity make Wire+Arc Additive Manufacturing a suitable candidate for replacing the current method of manufacturing from solid billets or large forgings, especially with regards to low and medium complexity parts. A variety of components have been successfully manufactured with this process, including Ti–6Al–4V spars and landing gear assemblies, aluminium wing ribs, steel wind tunnel models and cones. Strategies on how to manage residual stress, improve mechanical properties and eliminate defects such as porosity are suggested. Finally, the benefits of non-destructive testing, online monitoring and in situ machining are discussed.
1,051 citations
TL;DR: In this paper, the state-of-the-art with respect to inspection methodologies compatible with additively manufactured (AM) processes is explored with the intention of identifying new avenues for research and proposing approaches to integration into future generations of AM systems.
1,024 citations
Cites background from "Metal Additive Manufacturing: A Rev..."
...In addition, key reviews have been published in the area of applications and opportunities for AM techniques; these have centred around biomedical [6,7] aerospace [8], tooling [9] and general manufacturing [10]....
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References
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TL;DR: In this paper, the authors presented the various types of microstructure of the Ti-6Al-4V alloy after post-fabrication heat treatments below or above the β transus.
Abstract: Selective laser melting (SLM) is a rapid manufacturing process that enables the buildup of very complex parts in short delays directly from powder beds. Due to the high laser beam energy during very short interaction times and the high solidification rates of the melting pool, the resulting microstructure is out-of-equilibrium and particularly textured. This type of as-fabricated microstructure may not satisfy the aeronautical criterion and requires post heat treatments. Optimized heat treatments are developed, in one side, to homogenize and form the stable phases α and β while preventing exaggerated grain growth. In the other side, heat treatment is investigated to relieve the thermal stresses appearing during cooling. This study is aimed at presenting the various types of microstructure of the Ti-6Al-4V alloy after postfabrication heat treatments below or above the β transus. Tensile tests are then carried out at room temperature in order to assess the effect of the microstructures on the mechanical properties. The fine as-fabricated microstructure presents high yield and ultimate strengths, whereas the ductility is well below the standard. A strong anisotropy of fracture between the two loading directions is noted, which is attributed to the manufacturing defects. Conventional and optimized heat treatments exhibit high yield and ultimate strengths while the ductility is significantly improved. This is due to a new optimization of the process parameters allowing drastic reduction of the number of defects. These two heat treatments enable now a choice of the morphology of the grains between columnar or equiaxial as a function of the type of loading.
921 citations
TL;DR: In this paper, the macrostructure, microstructure and mechanical properties of a Ti-6Al-4V alloy after WAAM deposition have been investigated, and the average yield and ultimate tensile strengths of the as-deposited material were found to be slightly lower than those for a forged Ti- 6Al 4V bar (MIL-T 9047), however, the ductility was similar and the mean fatigue life was significantly higher.
Abstract: Wire and arc additive manufacturing (WAAM) is a novel manufacturing technique in which large metal components can be fabricated layer by layer. In this study, the macrostructure, microstructure, and mechanical properties of a Ti-6Al-4V alloy after WAAM deposition have been investigated. The macrostructure of the arc-deposited Ti-6Al-4V was characterized by epitaxial growth of large columnar prior-β grains up through the deposited layers, while the microstructure consisted of fine Widmanstatten α in the upper deposited layers and a banded coarsened Widmanstatten lamella α in the lower layers. This structure developed due to the repeated rapid heating and cooling thermal cycling that occurs during the WAAM process. The average yield and ultimate tensile strengths of the as-deposited material were found to be slightly lower than those for a forged Ti-6Al-4V bar (MIL-T 9047); however, the ductility was similar and, importantly, the mean fatigue life was significantly higher. A small number of WAAM specimens exhibited early fatigue failure, which can be attributed to the rare occurrence of gas pores formed during deposition.
512 citations
01 Sep 2006
TL;DR: In this article, a cost model for laser sintering is proposed, which leads to graph profiles that are typical for layer-by-layer manufacturing processes, and the evolution of cost models and the indirect cost significance in modern costing representation is shown.
Abstract: Rapid manufacturing (RM) is a modern production method based on layer by layer manufacturing directly from a three-dimensional computer-aided design model. The lack of tooling makes RM economically suitable for low and medium production volumes. A comparison with traditional manufacturing processes is important; in particular, cost comparison. Cost is usually the key point for decision making, with break-even points for different manufacturing technologies being the dominant information for decision makers. Cost models used for traditional production methodologies focus on material and labour costs, while modern automated manufacturing processes need cost models that are able to consider the high impact of investments and overheads. Previous work on laser sintering costing was developed in 2003. This current work presents advances and discussions on the limits of the previous work through direct comparison. A new cost model for laser sintering is then proposed. The model leads to graph profiles that are typical for layer-manufacturing processes. The evolution of cost models and the indirect cost significance in modern costing representation is shown finally.
331 citations
TL;DR: In this paper, the authors investigated three case studies to reveal the extent to which DMD-based manufacturing of molds and dies can currently achieve reduced environmental emissions and energy consumption relative to conventional manufacturing pathways.
298 citations
TL;DR: In this paper, the relationship between LAM processing parameters and microstructure in as-deposited Ti-6Al-4V was investigated, and the results presented in this paper provide a first look at the relationships between the two parameters.
Abstract: Laser additive manufacturing (LAM) is a manufacturing technique with cost-reduction potential for titanium aerospace components. The mechanical properties of LAM Ti-6Al-4V have been investigated extensively, but little work on microstructure evolution has been performed to date. The results presented here provide a first look at the relationships between LAM processing parameters and microstructure in as-deposited Ti-6Al-4V.
275 citations