Metal Additive Manufacturing Processes and Applications

A special issue of Metals (ISSN 2075-4701). This special issue belongs to the section "Additive Manufacturing".

Deadline for manuscript submissions: closed (31 January 2023) | Viewed by 8734

Special Issue Editor


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Guest Editor
Nuclear Materials Division, Korea Atomic Energy Research Institute, Daejeon 34057, Republic of Korea
Interests: powder metallurgy; material processing; plastic deformation; textures

Special Issue Information

Dear Colleagues,

The additive manufacturing technique, feasible for use with customized, small-scale production, is emerging and being highlighted as a replacement for mass production manufacturing technology. At present, however, metal additive manufacturing is not a complete technology that can directly replace conventional manufacturing methods. In terms of part shape implementation, two or more sequential processes are required, as the additive manufacturing method should be modified according to the size and minimum thickness of the part to be manufactured and the position and distribution of the overhang structure. It is also necessary to verify whether the mechanical properties are satisfactory through part performance tests, and post-treatment technologies are also required for the purpose of controlling the internal porosity and the surface roughness after additive manufacturing. In order to secure applicability and extensibility in the field of metal additive manufacturing, numerous technical verification efforts and data must be accumulated, and creative solutions must be sought. Therefore, this Special Issue will gather high-quality research efforts in the field of metal additive manufacturing that introduce the innovative efforts that are being made for successful technology settlement.

Dr. Suk Hoon Kang
Guest Editor

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Keywords

  • metal additive manufacturing
  • powder metallurgy
  • post processing
  • material properties
  • technology standardization

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Published Papers (2 papers)

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Research

17 pages, 4572 KiB  
Article
Pyrometrical Interlayer Temperature Measurement in WAAM of Thin Wall: Strategies, Limitations and Functionality
by Vinicius Lemes Jorge, Felipe Ribeiro Teixeira and Américo Scotti
Metals 2022, 12(5), 765; https://doi.org/10.3390/met12050765 - 29 Apr 2022
Cited by 10 | Viewed by 2865
Abstract
Significant efforts have been spent determining or monitoring interlayer temperatures (IT) to increase quality in Wire Arc Additive Manufacturing (WAAM). However, an uneven thermal profile in the wall and a temperature gradient along the layer length are expected after a thin wall layer [...] Read more.
Significant efforts have been spent determining or monitoring interlayer temperatures (IT) to increase quality in Wire Arc Additive Manufacturing (WAAM). However, an uneven thermal profile in the wall and a temperature gradient along the layer length are expected after a thin wall layer deposition, questioning the effectiveness of IT and its measuring approaches. After identifying the holistic meaning of IT, this work aimed at confronting two strategies using infrared pyrometers, elucidating their advantages and limitations for both open and closed-loop control. The proposed Upper and Sideward Pyrometer strategies were presented in detail and then assessed at different distances from the heat source. A calibration procedure was proposed. The results confirmed the existence of a natural temperature gradient along the wall. In addition, they showed how differently the arc heat affects the measured points (in intensity and steadiness) according to the strategy. Therefore, the interlayer temperature measured at a specific point on a part manufactured by WAAM should be taken as a reference and not an absolute value; the absolute value changes according to the measuring approach, sensor positioning and calibration. Using a temperature reference, both strategies can be used in open-loop control to reach repeatability (geometrical and metallurgical) between layers. However, the Sideward Pyrometer strategy is more recommended for feedback control of production, despite being less flexible. Full article
(This article belongs to the Special Issue Metal Additive Manufacturing Processes and Applications)
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21 pages, 5916 KiB  
Article
Spatter Formation and Splashing Induced Defects in Laser-Based Powder Bed Fusion of AlSi10Mg Alloy: A Novel Hydrodynamics Modelling with Empirical Testing
by Asif Ur Rehman, Muhammad Arif Mahmood, Peyman Ansari, Fatih Pitir, Metin Uymaz Salamci, Andrei C. Popescu and Ion N. Mihailescu
Metals 2021, 11(12), 2023; https://doi.org/10.3390/met11122023 - 14 Dec 2021
Cited by 21 | Viewed by 4997
Abstract
Powder spattering and splashing in the melt pool are common phenomena during Laser-based Powder Bed Fusion (LPBF) of metallic materials having high fluidity. For this purpose, analytical and computational fluid dynamics (CFD) models have been deduced for the LPBF of AlSi10Mg alloy. The [...] Read more.
Powder spattering and splashing in the melt pool are common phenomena during Laser-based Powder Bed Fusion (LPBF) of metallic materials having high fluidity. For this purpose, analytical and computational fluid dynamics (CFD) models have been deduced for the LPBF of AlSi10Mg alloy. The single printed layer’s dimensions were estimated using primary operating conditions for the analytical model. In CFD modelling, the volume of fluid and discrete element modelling techniques were applied to illustrate the splashing and spatter phenomena, providing a novel hydrodynamics CFD model for LPBF of AlSi10Mg alloy. The computational results were compared with the experimental analyses. A trial-and-error method was used to propose an optimized set of parameters for the LPBF of AlSi10Mg alloy. Laser scanning speed, laser spot diameter and laser power were changed. On the other hand, the powder layer thickness and hatch distance were kept constant. Following on, 20 samples were fabricated using the LPBF process. The printed samples’ microstructures were used to select optimized parameters for achieving defect-free parts. It was found that the recoil pressure, vaporization, high-speed vapor cloud, Marangoni flow, hydraulic pressure and buoyancy are all controlled by the laser-material interaction time. As the laser-AlSi10Mg material interaction period progresses, the forces presented above become dominant. Splashing occurs due to a combination of increased recoil pressure, laser-material interaction time, higher material’s fluidity, vaporization, dominancy of Marangoni flow, high-speed vapor cloud, hydraulic pressure, buoyancy, and transformation of keyhole from J-shape to reverse triangle-shape that is a tongue-like protrusion in the keyhole. In the LPBF of AlSi10Mg alloy, only the conduction mode melt flow has been determined. For multi-layers printing of AlSi10Mg alloy, the optimum operating conditions are laser power = 140 W, laser spot diameter = 180 µm, laser scanning speed = 0.6 m/s, powder layer thickness = 50 µm and hatch distance = 112 µm. These conditions have been identified using sample microstructures. Full article
(This article belongs to the Special Issue Metal Additive Manufacturing Processes and Applications)
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