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Additive Manufacturing of Metallic Materials: Characterization, Properties, and Modeling

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

Deadline for manuscript submissions: closed (31 March 2023) | Viewed by 30762

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Dr. Behzad Fotovvati

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Guest Editor

Additive Manufacturing Institute of Science and Technology (AMIST), University of Louisville, Louisville, KY 40292, USA
Interests: metal additive manufacturing; direct metal laser sintering; selective laser melting; titanium alloys; materials characterization; laser welding

Dr. Praveen Sathiyamoorthi

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Guest Editor

Indian Institute of Technology (BHU), Varanasi, India
Interests: additive manufacturing; severe plastic deformation; deformation behavior; creep; superplasticity
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Dr. Gangaraju Manogna Karthik

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Guest Editor

Department of Mechanical Engineering IIT, Indian Institute of Technology (BHU), Varanasi, India
Interests: additive manufacturing; materials joining; deformation behavior
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Special Issue Information

Dear Colleagues,

Additive manufacturing (AM) technologies are positioned to provide a disruptive transformation in how products are designed and manufactured. Metal AM technologies have provided sustainable production routes for metals. There are several advantages related to this technology: design freedom, reduction in raw material consumption, reduced inventory management need, etc. Developing advanced materials with mechanical properties that are superior to existing ones is a constant demand for several challenging applications. Research on this topic aims to explore unique strategies for developing advanced materials via an additive manufacturing route.

However, extending the application of AM to critical components requires a deeper understanding of the correlations between the process variables and the material properties and part geometry. AM is based on adding materials layer-wise and scanning the part geometry using a moving heat source in a prescribed scan pattern. As a result, the cyclic thermal history and cooling rates and, in turn, the microstructural and mechanical properties of AM parts are a function of location and process parameters. Understanding this variation and its correlation to material microstructure, defects, and temperature variations provides a better understanding of the metal AM processes and methods to improve them. The computational modeling of AM processes is one of the approaches taken by researchers in this field to gain an understanding of these correlations. Significant advances in this field have been achieved due to interdisciplinary research in related fields of computational mechanics and numerical methods.

This Special Issue aims to collect the latest developments in the field, written by well-known researchers who have contributed significantly to the field of metal AM.

In this Special Issue, original research articles and reviews are welcome. Research areas may include (but are not limited to) the following:

Innovative AM technologies and process parameter optimization;
AM process–geometry–property correlations;
AM process modeling and simulation;
Design, analysis, and additive manufacturing of porous metallic structures and scaffolds;
Design and development of TRIP and TWIP alloys, high-entropy alloys, and precipitation-strengthened alloys by additive manufacturing;
Mechanical and microstructural characterization of AM parts;
Tensile properties, fatigue, fracture, and failure analysis of AM parts.

Dr. Behzad Fotovvati
Dr. Praveen Sathiyamoorthi
Dr. Gangaraju Manogna Karthik
Guest Editors

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Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Metals is an international peer-reviewed open access monthly journal published by MDPI.

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Keywords

Metal Powder Bed Fusion
Direct Energy Deposition
Direct Metal Laser Sintering
Electron Beam Melting
Materials Characterization
Material Properties
Metallurgical Characterization
Computational Modeling
Thermal Modeling
Numerical Simulation

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Published Papers (10 papers)

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Research

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25 pages, 13814 KiB

Open AccessArticle

Process Parameter Optimization of 2507 Super Duplex Stainless Steel Additively Manufactured by the Laser Powder Bed Fusion Technique

by Ali Mulhi, Shirin Dehgahi, Prashant Waghmare and Ahmed J. Qureshi

Metals 2023, 13(4), 725; https://doi.org/10.3390/met13040725 - 7 Apr 2023

Cited by 11 | Viewed by 2696

Abstract

Laser powder bed fusion is an attractive technology for producing high-strength stainless steel alloys. Among the stainless steels, 2507 super duplex stainless steel (2507 SDSS) is known for its excellent combination of corrosion resistance and high strength. Although there are some studies that aimed at optimizing the laser powder bed fusion (LPBF) printing parameters to print highly dense 2507 SDSS parts; However, a full optimization study is not reported yet. This study aims at optimizing the printing parameters for 2507 SDSS, namely: laser power, scan speed, and hatch distance. The response surface methodology was used in generating a detailed design of experiment to investigate the different pore formation types over a wide energy density range (22.22–428.87 J/mm³), examine the effects of each process parameter and their interactions on the resulting porosity, and identify an optimized parameter set for producing highly dense parts. Different process parameters showed different pore formation mechanisms, with lack-of-fusion, metallurgical or gas, and keyhole regimes being the most prevalent pore types identified. The lack-of-fusion pores are observed to decrease significantly with increasing the energy density at low values. However, a gradual increase in the keyhole pores was observed at higher energy densities. An optimal energy density process window from 68.24 to 126.67 J/mm³ is identified for manufacturing highly dense (≥99.6%) 2507 SDSS parts. Furthermore, an optimized printing parameter set at a laser power of 217.4 W, a scan speed of 1735.7 mm/s, and a hatch distance of 51.3 µm was identified, which was able to produce samples with 99.961% relative density. Using the optimized parameter set, the as-built 2507 SDSS sample had a ferrite phase fraction of 89.3% with a yield and ultimate tensile strength of 1115.4 ± 120.7 MPa and 1256.7 ± 181.9 MPa, respectively. Full article

(This article belongs to the Special Issue Additive Manufacturing of Metallic Materials: Characterization, Properties, and Modeling)

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21 pages, 7737 KiB

Open AccessArticle

Surface Integrity of Cryogenically Finished Additively Manufactured and Conventional Ti-6Al-4V Alloy

by Pankaj Kumar Singh, Santosh Kumar and Pramod Kumar Jain

Metals 2023, 13(4), 693; https://doi.org/10.3390/met13040693 - 31 Mar 2023

Cited by 6 | Viewed by 1379

Abstract

Additive manufacturing (AM) is used for the fabrication of solid components of complex geometries for customized applications. However, AM-fabricated components frequently require finishing operations such as abrasive grinding, which causes a different surface characteristic compared to the conventionally manufactured components. Thus, it is essential to study the effect of process parameters and the heat treatment on surface quality of the AM components because these may behave differently to the conventional manufactured components. In this study, surface characteristics of AM samples of Ti-6Al-4V with a cryogenically cooled finishing operation is compared with that of conventionally processed samples. The samples under investigation were fabricated by two different methods, namely, Direct Metal Laser Sintering (DMLS) and conventional processing. The effect of the two processes on surface characteristics, such as microhardness, surface roughness, X-ray diffraction (XRD), and mechanical properties has been studied. The average surface roughness from cryogenic grinding was reduced by 27.25% and 23.15% for the AM, and 30.08% and 29.13% for conventional samples, as compared to dry and moist conditions, respectively. The finished DMLS and conventional samples showed increase of microhardness by 14.07%, 14.27%, 17.54% and 17.48%, 8.06%, 38.68%, in dry, moist, and cryogenic conditions, respectively. In cryogenic conditions, as the DOC and table feed increased, a greater increase in peak broadening was observed. The peak broadening in XRD of finished DMLS components indicates that a significant level of plastic deformation occurred compared to the finished conventionally manufactured Ti-6Al-4V samples, which suggests that the DMLS samples are more sensitive to the finishing process. Compared to dry and moist grinding, cryogenic grinding was found to have the smallest grains in the layer just below the surface. The impact of cryogenic cooling on surface properties of AM Ti-6Al-4V samples is higher as compared to that on conventionally processed Ti-6Al-4V samples. Full article

(This article belongs to the Special Issue Additive Manufacturing of Metallic Materials: Characterization, Properties, and Modeling)

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22 pages, 13796 KiB

Open AccessArticle

Effects of Build Orientations on Microstructure Evolution, Porosity Formation, and Mechanical Performance of Selective Laser Melted 17-4 PH Stainless Steel

by Mohammad Azlan Aripin, Zainuddin Sajuri, Nashrah Hani Jamadon, Amir Hossein Baghdadi, Junaidi Syarif, Intan Fadhlina Mohamed and Ahmad Muhammad Aziz

Metals 2022, 12(11), 1968; https://doi.org/10.3390/met12111968 - 17 Nov 2022

Cited by 13 | Viewed by 2859

Abstract

In this study, the effect of phase, microstructure, and porosity in Selective Laser Melting (SLM) on hardness, tensile, and fracture behavior of 17-4 PH was investigated. The increasing interest in SLM in producing complex parts has encouraged the industry to produce performance parts, such as martensitic 17-4 PH stainless steel. However, the microstructure and mechanical behavior of SLM 17-4PH is not fully understood by researchers. Understanding the microstructure profile is complex because it is driven by thermal history and porosity. Both elements vary, based on the build directions, further hindering researchers from fully understanding the mechanical properties. To fabricate specimens in three different building orientations (0°, 45°, and 90°), 17-4 powder was used. Two phases, namely, austenite and martensite, with 90° build direction, retained more austenite, due to the reheating process on a smaller base area. The optical microstructure revealed several elements that were distinct for SLM processing, including circular, columnar lath, wave melt pool, and porosity. Columnar lath was found to grow continuously across different melt pools. Hardness was found to be higher for 0° than for 90°, due to higher martensite content. Tensile strength was highest for 0°, at 958 MPa, higher than at 45° and 90° at 743 and 614 MPa, respectively. Porosity analysis validated that 90° had all three types of porosities and, specifically, the crescent type, which held un-melted powders. All types of porosities were found in fractography analysis. Full article

(This article belongs to the Special Issue Additive Manufacturing of Metallic Materials: Characterization, Properties, and Modeling)

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14 pages, 8962 KiB

Open AccessArticle

CFD–DPM Simulation Study of the Effect of Powder Layer Thickness on the SLM Spatter Behavior

by Liu Cao, Qindan Zhang and Ruifan Meng

Metals 2022, 12(11), 1897; https://doi.org/10.3390/met12111897 - 5 Nov 2022

Cited by 3 | Viewed by 2493

Abstract

Selective Laser Melting (SLM) has significant advantages in manufacturing complex structural components and refining the alloy microstructure; however, spatter, as a phenomenon that accompanies the entire SLM forming process, is prone to problems such as inclusions, porosity, and low powder recovery quality. In this paper, a Computational Fluid Dynamics–Discrete Particle Method (CFD–DPM) simulation flow for predicting the SLM spatter behavior is established based on the open-source code OpenFOAM. Among them, the single-phase flow Navier–Stokes equation is used in the Eulerian framework to equivalently describe the effect of metal vapor and protective gas on the flow field of the forming cavity, and the DPM method is used in the Lagrangian framework to describe the metal particle motion, and the factors affecting the particle motion include particle–particle collision, particle–wall collision, fluid drag force, gravity, buoyancy force, and additional mass force. In addition, the equivalent volume force and fluid drag force are used to characterize the fluid–particle coupling interaction. For the spatter behavior and powder bed denudation phenomenon, the calculation results show that the spatter height and the drop location show a clear correlation, and the powder bed denudation phenomenon is caused by the high-speed gas flow, causing the surrounding gas to gather in the forming area, which in turn drives the motion of the powder bed particles. For the effect of powder layer thickness on spatter and powder bed denudation, the calculation results show that the effect of powder layer thickness on the number of spatters is large (when the thickness was increased from 50 μm to 100 μm, the number of spatters increased by 157%), but the effect on spatter height and drop location distribution is small. When the powder layer thickness is small, the width of the denudation zone is significantly larger, but when the powder layer reaches a certain thickness, the width of the denudation zone does not show significant changes. It should be noted that the presented model has not been directly validated by experiments so far due to the difficulty of tracking the large-scale motion of SLM spatter in real time by current experimental means. Full article

(This article belongs to the Special Issue Additive Manufacturing of Metallic Materials: Characterization, Properties, and Modeling)

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17 pages, 11404 KiB

Open AccessArticle

Experimental and Calphad Methods for Evaluating Residual Stresses and Solid-State Shrinkage after Solidification

by Atte Antikainen, Joni Reijonen, Juha Lagerbom, Matti Lindroos, Tatu Pinomaa and Tomi Lindroos

Metals 2022, 12(11), 1894; https://doi.org/10.3390/met12111894 - 5 Nov 2022

Cited by 3 | Viewed by 1779

Abstract

Laser powder bed fusion is an additive manufacturing method that is based on melting and solidification of powder material. Due to the local heating above the melting point, thermal stresses are usually formed in the final part. Mitigation of residual stresses is usually assessed by laser scan strategies and not by alloy tailoring. In this paper a segregation-based residual stress formation mechanism is proposed and assessed computationally. Additionally, an experimental setup for rapid screening of residual stress formation in various alloys is proposed. The results should ease material development of metal alloys tailored for additive manufacturing by allowing the comparison of residual stress formation tendency (e.g., solid state shrinkage) between alloys. The proposed computational method is comparative in nature and forecasting absolute residual stress values would require known temperature dependent elastoplastic properties for the alloys as well as exact thermal history. The proposed experimental method is quantitative but its reliability depends on material properties such as yield strength. Full article

(This article belongs to the Special Issue Additive Manufacturing of Metallic Materials: Characterization, Properties, and Modeling)

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14 pages, 6446 KiB

Open AccessArticle

Microstructural Investigation of a FeMnAlNi Shape Memory Alloy Processed by Tungsten Inert Gas Wire and Arc Additive Manufacturing

by Vincent Fabian Viebranz, Thomas Hassel and Hans Jürgen Maier

Metals 2022, 12(10), 1731; https://doi.org/10.3390/met12101731 - 16 Oct 2022

Cited by 3 | Viewed by 1811

Abstract

In the present study, tungsten inert gas wire and arc additive manufacturing was used to process an iron-based FeMnAlNi shape memory alloy. By a layer-by-layer method, a wall structure with a length of 60 mm and a height of 40 mm was generated. Bidirectional welding ensured grain growth parallel to the building direction. To maintain a nearly constant temperature–time path upon cooling, the structure was fully cooled after each weld to room temperature (298 K). With this approach, an anisotropic microstructure with a grain length of up to 8 mm (major axis) could be established. The grain morphology and formed phases were investigated by optical microscopy and scanning electron microscopy. The images revealed a difference in the orientation with respect to the building direction of the primarily formed γ grains along the grain boundaries and the secondarily formed γ grains in the heat-affected zones. Subgrains in the α matrix were observed also by scanning electron microscopy. With X-ray diffraction, the preferred orientation of the α grains with respect to the building direction was found to be near ⟨100⟩. Overall, an anisotropic polycrystalline material with a columnar texture could be produced, with a preferred grain orientation promising high values of transformation strains. Full article

(This article belongs to the Special Issue Additive Manufacturing of Metallic Materials: Characterization, Properties, and Modeling)

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15 pages, 7554 KiB

Open AccessFeature PaperArticle

Numerical Modeling of Distortion of Ti-6Al-4V Components Manufactured Using Laser Powder Bed Fusion

by Patiparn Ninpetch, Pruet Kowitwarangkul, Prasert Chalermkarnnon, Patcharapit Promoppatum, Piyapat Chuchuay and Phadungsak Rattanadecho

Metals 2022, 12(9), 1484; https://doi.org/10.3390/met12091484 - 8 Sep 2022

Cited by 10 | Viewed by 2452

Abstract

The laser powder bed fusion (L-PBF) process is a powder-based additive manufacturing process that can manufacture complex metallic components. However, when the metallic components are fabricated with the L-PBF process, they frequently encounter the residual stress and distortion that occurs due to the cyclic of rapid heating and cooling. The distortion detrimentally impacts the dimensional and geometrical accuracy of final built parts in the L-PBF process. The purpose of this research was to explore and predict the distortion of Ti-6Al-4V components manufactured using the L-PBF process by using numerical modeling in Simufact Additive 2020 FP1 software. Firstly, the numerical model validation was conducted with the twin-cantilever beam part. Later, studies were carried out to examine the effect of component sizes and support-structure designs on the distortion of tibial component produced by the L-PBF process. The results of this research revealed a good agreement between the numerical model and experiment data. In addition, the platform was extended to predict the distortion in the tibial component. Large distortion arose near the interface between the tibial tray and support structure due to the different stiffness between the solid bulk and support structure. The distortion of the tibial component increased with increasing component size according to the surface area of the tibial tray, and with increasing thickness of the tibial tray. Furthermore, the support-structure design plays an important role in distortion reduction in the L-PBF process. For example, the maximum distortion of the tibial component was minimized up to 44% when a block support-structure design with a height of 2.5 mm was used instead of the lattice-based support. The present study provides useful information to help the medical sector to manufacture effective medical components and reduce the chance of part failure from cracking in the L-PBF process. Full article

(This article belongs to the Special Issue Additive Manufacturing of Metallic Materials: Characterization, Properties, and Modeling)

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15 pages, 4573 KiB

Open AccessFeature PaperArticle

The Influence of Processing Parameters on the Al-Mn Enriched Nano-Precipitates Formation in a Novel Al-Mn-Cr-Zr Alloy Tailored for Power Bed Fusion-Laser Beam Process

by Alessandra Martucci, Bharat Mehta, Mariangela Lombardi and Lars Nyborg

Metals 2022, 12(8), 1387; https://doi.org/10.3390/met12081387 - 20 Aug 2022

Cited by 3 | Viewed by 2138

Abstract

Among the recently developed compositions tailored for the power bed fusion-laser beam process (PBF-LB), the novel Al-Mn-Cr-Zr alloy stands out. This composition exploits high solid solution strengthening, achieving a high hardness value in the as-built condition. The produced samples are inherently crack-free and have a good level of densification (~99.5%). The goal of this study is to investigate how this quaternary system is affected by the laser power while retaining a similar volumetric energy density. A comparison between the microstructural features and the mechanical performance was performed on a set of samples processed with power values ranging from 100 to 170 W. Microstructural features were investigated through optical microscopy, Electron Back Scattered Diffraction (EBSD) investigation and feature analysis using advanced microscopy to examine the amount, distribution, and shape of precipitates in the different process conditions. Although the quantitative feature analysis permitted analysis of more than 60 k precipitates for each power condition, all samples demonstrated a low level of precipitation (below 0.3%) with nanometric size (around 75 nm). The mechanical performances of this quaternary system as a function of the laser power value were evaluated with a microhardness test, recording very similar values for the different process conditions with a mean value of approximately 104 HV. The results suggested a very stable system over the tested range of process parameters. In addition, considering the low level of precipitation of nanometric phases enriched in Al-Mn, a supersaturated state could be established in each process condition. Full article

(This article belongs to the Special Issue Additive Manufacturing of Metallic Materials: Characterization, Properties, and Modeling)

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14 pages, 3238 KiB

Open AccessArticle

Microstructure, Mechanical Properties, and Corrosion Behavior of 06Cr15Ni4CuMo Processed by Using Selective Laser Melting

by Jayaraman Maya, Katakam Sivaprasad, Guttula Venkata Sarath Kumar, Rustam Baitimerov, Pavel Lykov and Konda Gokuldoss Prashanth

Metals 2022, 12(8), 1303; https://doi.org/10.3390/met12081303 - 3 Aug 2022

Cited by 9 | Viewed by 2315

Abstract

A new class of martensitic stainless steel, namely 06Cr15Ni4CuMo, with applications in marine engineering, was processed by using selective laser melting (SLM). A body-centered cubic martensitic microstructure was observed, and the microstructure was compared with wrought 410 martensitic stainless steel. The SLM-processed sample showed a hardness of 465 ± 10 HV_0.5, which was nearly 115 HV_0.5 less than the wrought counterpart. Similarly, the SLM-processed sample showed improved YS and UTS, compared with the wrought sample. However, reduced ductility was observed in the SLM-processed sample due to the presence of high dislocation density in these samples. In addition, 71% volume high-angle grain boundaries were observed, corroborating the high strength of the material. The corrosion behavior was investigated in seawater, and the corrosion resistance was found to be 0.025 mmpy for the SLM-processed 06Cr15Ni4CuMo steel and 0.030 mmpy for wrought 410 alloys, showing better corrosion resistance in the SLM-processed material. Full article

(This article belongs to the Special Issue Additive Manufacturing of Metallic Materials: Characterization, Properties, and Modeling)

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Review

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34 pages, 5535 KiB

Open AccessReview

Additively Manufactured Porous Ti6Al4V for Bone Implants: A Review

by Naresh Koju, Suyash Niraula and Behzad Fotovvati

Metals 2022, 12(4), 687; https://doi.org/10.3390/met12040687 - 16 Apr 2022

Cited by 54 | Viewed by 9314

Abstract

Ti-6Al-4V (Ti64) alloy is one of the most widely used orthopedic implant materials due to its mechanical properties, corrosion resistance, and biocompatibility nature. Porous Ti64 structures are gaining more research interest as bone implants as they can help in reducing the stress-shielding effect when compared to their solid counterpart. The literature shows that porous Ti64 implants fabricated using different additive manufacturing (AM) process routes, such as laser powder bed fusion (L-PBF) and electron beam melting (EBM) can be tailored to mimic the mechanical properties of natural bone. This review paper categorizes porous implant designs into non-gradient (uniform) and gradient (non-uniform) porous structures. Gradient porous design appears to be more promising for orthopedic applications due to its closeness towards natural bone morphology and improved mechanical properties. In addition, this paper outlines the details on bone structure and its properties, mechanical properties, fatigue behavior, multifunctional porous implant designs, current challenges, and literature gaps in the research studies on porous Ti64 bone implants. Full article

(This article belongs to the Special Issue Additive Manufacturing of Metallic Materials: Characterization, Properties, and Modeling)

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