Additive Manufacturing Processes in Metals

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

Deadline for manuscript submissions: closed (30 November 2021) | Viewed by 9944

Special Issue Editor

Oak Ridge National Laboratory, Oak Ridge, TN 37830, USA
Interests: metal additive manufacturing; cracking in Ni-based superalloy; process–microstructure–property relationship; thermomechanical simulation; melt pool solidification; powder particle simulation; scan strategy

Special Issue Information

Dear Colleagues,

Additive manufacturing (AM) has the potential to revolutionize the way of traditional manufacturing design and technologies. The manufacturing envelope can be micron to meter-scale and can take days or even weeks to print. For this technology to be adopted for manufacturing of critical structural components, tight control of process parameters, part properties, and performance is required for various AM processes (e.g., laser, electron beam, arc, binder jetting). Under dynamic printing conditions and complex part geometries, the part is primarily associated with varying thermal cycles influencing phase transformation and internal stress buildup. This can degrade the local part properties, causing cracking or catastrophic failure of a critical component. Although there are extensive advances in the welding and metal AM community, challenges still hinder the wide adoption of this technology to aerospace or automotive or other industries. This Special Issue of Metals focuses on advanced research activities in metal additive manufacturing processes. Your contribution to this Special Issue is highly valued for readers from academia, industry, and other research organizations.

Dr. Yousub Lee
Guest Editor

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Keywords

  • Process parameter optimization: thermal and property control method to manage metallurgical transformation, mechanical properties, and part deformation
  • In situ process monitoring and defect quantification in metal AM
  • Efficient modeling and simulations and machine learning aided design to understand process–microstructure–property correlation
  • Developing new alloys or dissimilar parts fabricated by metal AM
  • Effect of part building strategy and post-heat treatment to obtain desired part properties

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Published Papers (3 papers)

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Research

18 pages, 9374 KiB  
Article
Ti-6Al-4V Octet-Truss Lattice Structures under Bending Load Conditions: Numerical and Experimental Results
by Francesco Di Caprio, Stefania Franchitti, Rosario Borrelli, Costanzo Bellini, Vittorio Di Cocco and Luca Sorrentino
Metals 2022, 12(3), 410; https://doi.org/10.3390/met12030410 - 26 Feb 2022
Cited by 12 | Viewed by 3598
Abstract
Metal lattice structures produced by means of additive techniques are attracting increasing attention thanks to the high structural efficiency they can offer. In order to achieve the maximum structural performance, numerical design techniques are used almost exclusively, thus based on CAE-FEM codes. Nevertheless, [...] Read more.
Metal lattice structures produced by means of additive techniques are attracting increasing attention thanks to the high structural efficiency they can offer. In order to achieve the maximum structural performance, numerical design techniques are used almost exclusively, thus based on CAE-FEM codes. Nevertheless, the current manufacturing facilities do not yet guarantee defect-free components, and, therefore, such imperfections need to be introduced in the numerical models too. The present work aims to describe a FE modelling technique for lattice structures based on the use of beam and shell elements, and therefore with a very reduced computational cost. The main structural parameters, such as weight and stiffness and strength, are used to drive the model calibration. Simple mathematical relationships, based on Experimental-CAD-FEM comparisons, are provided to estimate the error related to the numerical model in a simple and fast way. The validation was performed by three-point bending test on flat specimen with regular octet-truss microstructure both with and without external skin. The test articles were produced in Ti6Al4V and by means of the electron beam melting (EBM) technology. The results obtained are in excellent agreement with the experimental ones, indeed the maximum error is about 3%. All this indicates these methodologies as possible tools for evaluating the performance of such kinds of high-tech structures. Full article
(This article belongs to the Special Issue Additive Manufacturing Processes in Metals)
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21 pages, 33585 KiB  
Article
Identification of a Spatio-Temporal Temperature Model for Laser Metal Deposition
by Matthias Kahl, Sebastian Schramm, Max Neumann and Andreas Kroll
Metals 2021, 11(12), 2050; https://doi.org/10.3390/met11122050 - 18 Dec 2021
Cited by 6 | Viewed by 2937
Abstract
Laser-based additive manufacturing enables the production of complex geometries via layer-wise cladding. Laser metal deposition (LMD) uses a scanning laser source to fuse in situ deposited metal powder layer by layer. However, due to the excessive number of influential factors in the physical [...] Read more.
Laser-based additive manufacturing enables the production of complex geometries via layer-wise cladding. Laser metal deposition (LMD) uses a scanning laser source to fuse in situ deposited metal powder layer by layer. However, due to the excessive number of influential factors in the physical transformation of the metal powder and the highly dynamic temperature fields caused by the melt pool dynamics and phase transitions, the quality and repeatability of parts built by this process is still challenging. In order to analyze and/or predict the spatially varying and time dependent thermal behavior in LMD, extensive work has been done to develop predictive models usually by using finite element method (FEM). From a control-oriented perspective, simulations based on these models are computationally too expensive and are thus not suitable for real-time control applications. In this contribution, a spatio-temporal input–output model based on the heat equation is proposed. In contrast to other works, the parameters of the model are directly estimated from measurements of the LMD process acquired with an infrared (IR) camera during processing specimens using AISI 316 L stainless steel. In order to deal with noisy data, system identification techniques are used taking different disturbing noise into account. By doing so, spatio-temporal models are developed, enabling the prediction of the thermal behavior by means of the radiance measured by the IR camera in the range of the considered processing parameters. Furthermore, in the considered modeling framework, the computational effort for thermal prediction is reduced compared to FEM, thus enabling the use in real-time control applications. Full article
(This article belongs to the Special Issue Additive Manufacturing Processes in Metals)
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13 pages, 30787 KiB  
Article
Effects of Gas Pressure during Electron Beam Energy Deposition in the EBM Additive Manufacturing Process
by Elroei Damri, Eitan Tiferet, Dor Braun, Yaron Itay Ganor, Michael Chonin and Itzhak Orion
Metals 2021, 11(4), 601; https://doi.org/10.3390/met11040601 - 7 Apr 2021
Cited by 6 | Viewed by 2728
Abstract
Electron beam melting (EBM) is a metal powder bed fusion additive manufacturing (AM) technology that facilitates the production of metal parts by selectively melting areas in layers of metal powder. The electron beam melting process is conducted in a vacuum chamber environment regulated [...] Read more.
Electron beam melting (EBM) is a metal powder bed fusion additive manufacturing (AM) technology that facilitates the production of metal parts by selectively melting areas in layers of metal powder. The electron beam melting process is conducted in a vacuum chamber environment regulated with helium (He) at a pressure on the scale of 10−3 mbar. One of the disadvantages of vacuum environments is the effect of vapor pressure on volatile materials: indeed, elements in the pre-alloyed powder with high vapor pressure are at risk of evaporation. Increasing the He pressure in the process can improve the thermodynamic stability of the pre-alloyed components and decrease the composition volatility of the solid. However, increasing the pressure can also attenuate the electrons and consequently reduce the energy deposition efficiency. While it is generally assumed that the efficiency of the process is 90%, to date no studies have verified this. In this study, Monte Carlo simulations and detailed thermal experiments were conducted utilizing EGS5 and an Arcam Q20+ machine. The results reveal that increasing the gas pressure in the vacuum chamber by one order of magnitude (from 10−3 mbar to 10−2 mbar) did not significantly reduce the energy deposition efficiency (less than 1.5%). The increase in gas pressure will enable the melting of alloys with high vapor pressure elements in the future. Full article
(This article belongs to the Special Issue Additive Manufacturing Processes in Metals)
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