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.
Citations
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TL;DR: In this article, the authors investigated the anisotropic mechanical properties of a Ti-6Al-4V three-dimensional cruciform component fabricated using a directed energy deposition additive manufacturing (AM) process.
983 citations
Cites background from "Metal Additive Manufacturing: A Rev..."
...Material can be delivered to the workpiece either by spreading and selectively melting individual powder layers in a powder bed fusion (PBF) process, or directed continuously through coaxial nozzles to the melt pool in a directed energy deposition (DED) process [5,6]....
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TL;DR: In this paper, the impact of friction and wear on energy consumption, economic expenditure, and CO2 emissions is presented on a global scale, covering four main energy consuming sectors: transportation, manufacturing, power generation, and residential.
Abstract: Calculations of the impact of friction and wear on energy consumption, economic expenditure, and CO2 emissions are presented on a global scale. This impact study covers the four main energy consuming sectors: transportation, manufacturing, power generation, and residential. Previously published four case studies on passenger cars, trucks and buses, paper machines and the mining industry were included in our detailed calculations as reference data in our current analyses. The following can be concluded:
Fifty years ago, wear and wear-related failures were a major concern for UK industry and their mitigation was considered to be the major contributor to potential economic savings by as much as 95% in ten years by the development and deployment of new tribological solutions. The corresponding estimated savings are today still of the same orders but the calculated contribution to cost reduction is about 74% by friction reduction and to 26% from better wear protection. Overall, wear appears to be more critical than friction as it may result in catastrophic failures and operational breakdowns that can adversely impact productivity and hence cost.
966 citations
TL;DR: A broad range of metal additive manufacturing (AM) technologies and reviews literatures on the anisotropy and heterogeneity of microstructure and mechanical properties for metal AM parts are presented in this paper.
799 citations
Cites background or methods from "Metal Additive Manufacturing: A Rev..."
...Metal AM parts usually undergo complex cyclic thermal history consisting of directional heat extraction, repeated melting and rapid solidification [21, 26], which would create anisotropic and heterogeneous microstructures that intrinsically differed from the metallic parts manufactured via conventional methods [11, 12]....
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...There have been extensive studies on the microstructure, mechanical properties, and processability of various metals and alloys in a variety of metal AM systems [8, 9, 20-22]....
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...Many studies have shown that the tensile properties of AM-processed Ti-6Al-4V are comparable to their cast and wrought material equivalents [9, 11, 21, 95]....
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...Generic illustrations of a DED AM systems: (a) powder-blown system, (b) wire-fed system [21]....
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TL;DR: A comprehensive understanding of the interrelation between the various aspects of the subject, as this is essential to demonstrate credibility for industrial needs, is presented in this paper, which highlights some key topics requiring attention for further progression.
761 citations
TL;DR: In this paper, the authors review the current state of the art and describe the challenges that need to be met to achieve the desired fundamental understanding of the physics of the additive manufacturing process.
Abstract: The production of metal parts via laser powder bed fusion additive manufacturing is growing exponentially. However, the transition of this technology from production of prototypes to production of critical parts is hindered by a lack of confidence in the quality of the part. Confidence can be established via a fundamental understanding of the physics of the process. It is generally accepted that this understanding will be increasingly achieved through modeling and simulation. However, there are significant physics, computational, and materials challenges stemming from the broad range of length and time scales and temperature ranges associated with the process. In this paper, we review the current state of the art and describe the challenges that need to be met to achieve the desired fundamental understanding of the physics of the process.
758 citations
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