Additively Manufactured Alloys: Process, Microstructure and Properties

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

Deadline for manuscript submissions: closed (31 December 2022) | Viewed by 9737

Special Issue Editors


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Guest Editor
College of Engineering & Computer Science, University of Central Florida, Orlando, FL 32816, USA
Interests: physical metallurgy; diffusion; microstructure; additive manufacturing; powder metallurgy; protective coatings; high temperature alloys
Opus College of Engineering, Marquette University, 1515 W. Wisconsin Ave., Milwaukee, WI 53233, USA
Interests: physical metallurgy; phase transformation; creep and fatigue; additive manufacturing; hot isostatic pressing; lightweight alloys; superalloy

Special Issue Information

Dear Colleagues,

Additive manufacturing (AM) for metallic alloys represents a technological platform to produce the customized, on-demand, and even on-site production of engineering components. Moreover, it presents an opportunity to design and develop new and/or modified metallic alloys that can desensitize inherent AM process variables and take advantage of unique thermo-kinetic environments which can lead to novel microstructure and properties. We would like to invite your contribution to add to the rapidly expanding body of knowledge that would establish the fundamental processing-structure-properties relations in additively manufactured metallic alloys. We seek contributions that elucidate the AM process optimization, detailed microstructural analysis and assessment of properties such as mechanical and other functional properties. This Special Issue would help to establish a new paradigm in advanced materials development with built-in component manufacturing considerations by utilizing the AM technology as tools to rapidly produce, characterize and assess metallic alloys.

Prof. Dr. Yongho Sohn
Dr. Le Zhou
Guest Editors

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Keywords

  • additive manufacturing
  • metals and alloys
  • processing-structure-properties relations
  • processing optimization
  • microstructural analysis
  • properties assessment

Published Papers (4 papers)

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Research

21 pages, 3859 KiB  
Article
Microstructures and Hardening Mechanisms of a 316L Stainless Steel/Inconel 718 Interface Additively Manufactured by Multi-Material Selective Laser Melting
by Shahir Mohd Yusuf, Nurainaa Mazlan, Nur Hidayah Musa, Xiao Zhao, Ying Chen, Shoufeng Yang, Nur Azmah Nordin, Saiful Amri Mazlan and Nong Gao
Metals 2023, 13(2), 400; https://doi.org/10.3390/met13020400 - 15 Feb 2023
Cited by 6 | Viewed by 1863
Abstract
For the first time, the interfacial microstructures and hardening mechanisms of a multi-material (MM) 316L stainless steel/Inconel 718 (316L SS/IN 718) interface fabricated by a novel multi-material selective laser melting (MM SLM) additive manufacturing (AM) system have been investigated in this study. MM [...] Read more.
For the first time, the interfacial microstructures and hardening mechanisms of a multi-material (MM) 316L stainless steel/Inconel 718 (316L SS/IN 718) interface fabricated by a novel multi-material selective laser melting (MM SLM) additive manufacturing (AM) system have been investigated in this study. MM 316L SS/IN 718 parts were successfully built with high densification levels (>99%) and low porosity content (average: ~0.81%). Microscopy analysis indicates that the interfacial microstructures are characterised by dense dislocation tangling networks, NbC and TiC, and very small amounts of Laves phase (<2 wt. %). In addition, equiaxed grains (average: 45 ± 3 μm) are attained in the interfacial region, whereas both individual IN 718 and 316L SS regions exhibit show columnar grains with average sizes of 55 ± 5 μm and 85 ± 3 μm, respectively. Vickers microhardness (HV) and nanoindentation measurements exhibit that the hardness values of the interfacial region are between those of the individual material regions. A strengthening model is built to assess the contribution of intrinsic strength, solid solution, precipitations, dislocations, and grain boundaries to the overall interfacial hardness of the as-built MM alloy. Full article
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12 pages, 7034 KiB  
Article
Hardness Evolution of Solution-Annealed LPBFed Inconel 625 Alloy under Prolonged Thermal Exposure
by Fabrizio Marinucci, Giulio Marchese, Emilio Bassini, Alberta Aversa, Paolo Fino, Daniele Ugues and Sara Biamino
Metals 2022, 12(11), 1916; https://doi.org/10.3390/met12111916 - 9 Nov 2022
Cited by 1 | Viewed by 1321
Abstract
Thanks to its high weldability, Inconel 625 (IN625) can be easily processed by laser powder bed fusion (LPBF). After production, this alloy is typically subjected to specific heat treatments to design specific microstructure features and mechanical performance suitable for various industrial applications, including [...] Read more.
Thanks to its high weldability, Inconel 625 (IN625) can be easily processed by laser powder bed fusion (LPBF). After production, this alloy is typically subjected to specific heat treatments to design specific microstructure features and mechanical performance suitable for various industrial applications, including aeronautical, aerospace, petrochemical, and nuclear fields. When employed in structural applications, IN625 can be used up to around 650 °C. This limitation is mainly caused by the transformation of metastable γ″ phases into stable δ phases occurring under prolonged thermal exposure, which results in drastically reduced ductility and toughness of the alloy. Because the microstructure and mechanical properties change during thermal exposure, it is essential to study the material simulating possible service temperatures. In the current study, LPBFed IN625 samples were solution-annealed and then subjected to thermal exposure at 650 °C for different times up to 2000 h. The characterization focused on the evolution of the main phases, γ″ and δ phases, and their influence on the hardness evolution. The microstructure and hardness of the heat-treated LPBFed IN625 samples were compared with data related to the traditionally processed IN625 alloy (e.g., wrought state) reported in the literature. Full article
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16 pages, 5749 KiB  
Article
Determination of Location-Specific Solidification Cracking Susceptibility for a Mixed Dissimilar Alloy Processed by Wire-Arc Additive Manufacturing
by Soumya Sridar, Noah Sargent, Xin Wang, Michael A. Klecka and Wei Xiong
Metals 2022, 12(2), 284; https://doi.org/10.3390/met12020284 - 5 Feb 2022
Cited by 4 | Viewed by 2438
Abstract
Solidification cracking is a major obstacle when joining dissimilar alloys using additive manufacturing. In this work, location-specific solidification cracking susceptibility has been investigated using an integrated computational materials engineering (ICME) approach for a graded alloy formed by mixing P91 steel and Inconel 740H [...] Read more.
Solidification cracking is a major obstacle when joining dissimilar alloys using additive manufacturing. In this work, location-specific solidification cracking susceptibility has been investigated using an integrated computational materials engineering (ICME) approach for a graded alloy formed by mixing P91 steel and Inconel 740H superalloy. An alloy mixture of 26 wt.% P91 and 74 wt.% Inconel 740H, with high configurational and total entropy, was fabricated using wire arc additive manufacturing. Microstructure characterization revealed intergranular solidification cracks in the FCC matrix, which increased in length along with the enrichment of Nb (~27 to 56 wt.%) and Cu (~87 wt.%) in the middle and top regions. DICTRA simulations to model location-specific solidification cracking susceptibility showed that the top region with the highest cooling rate (270 K/s) has the highest solidification cracking susceptibility in comparison with the middle and bottom regions. This is in good agreement with the experimentally observed varying crack length. From Scheil simulations, it was deduced that enrichment of Nb and Cu affected the solidification range as high as ~77%, in comparison with the matrix composition. The overall solidification cracking susceptibility and freezing range was highest for the 26 wt.% P91 alloy amongst the mixed compositions between P91 steel and 740H superalloy, proving that solidification characteristics play a major role in alloy design for additive manufacturing. Full article
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17 pages, 14802 KiB  
Article
Mechanical Behavior Assessment of Ti-6Al-4V ELI Alloy Produced by Laser Powder Bed Fusion
by Asif Mahmud, Thinh Huynh, Le Zhou, Holden Hyer, Abhishek Mehta, Daniel D. Imholte, Nicolas E. Woolstenhulme, Daniel M. Wachs and Yongho Sohn
Metals 2021, 11(11), 1671; https://doi.org/10.3390/met11111671 - 20 Oct 2021
Cited by 17 | Viewed by 3281
Abstract
The present work correlates the quasi-static, tensile mechanical properties of additively manufactured Ti-6Al-4V extra low interstitial (ELI, Grade 23) alloy to the phase constituents, microstructure, and fracture surface characteristics that changed with post-heat treatment of stress relief (670 °C for 5 h) and [...] Read more.
The present work correlates the quasi-static, tensile mechanical properties of additively manufactured Ti-6Al-4V extra low interstitial (ELI, Grade 23) alloy to the phase constituents, microstructure, and fracture surface characteristics that changed with post-heat treatment of stress relief (670 °C for 5 h) and hot isostatic pressing (HIP with 100 MPa at 920 °C for 2 h under an Ar atmosphere). Ti-6Al-4V ELI alloy tensile specimens in both the horizontal (i.e., X and Y) and vertical (Z) directions were produced by the laser powder bed fusion (LPBF) technique. Higher yield strength (1141 MPa), higher tensile strength (1190 MPa), but lower elongation at fracture (6.9%), along with mechanical anisotropy were observed for as-stress-relieved (ASR) samples. However, after HIP, consistent and isotropic mechanical behaviors were observed with a slight reduction in yield strength (928 MPa) and tensile strength (1003 MPa), but with a significant improvement in elongation at fracture (16.1%). Phase constituents of acicular α′ phase in ASR and lamellar α + β phases in HIP samples were observed and quantified to corroborate the reduction in strength and increase in ductility. The anisotropic variation in elongation at fracture observed for the ASR samples, particularly built in the build (Z) direction, was related to the presence of “keyhole” porosity. Full article
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