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Additive Manufacturing of Metals and Alloys: Microstructure and Mechanical Properties

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A special issue of Materials (ISSN 1996-1944). This special issue belongs to the section "Metals and Alloys".

Deadline for manuscript submissions: closed (20 September 2025) | Viewed by 10591

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Dr. Federico Mazzucato

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ARM Laboratory, Department of Innovative Technologies, University of Applied Sciences and Arts of Southern Switzerland (SUPSI), CH-6962 Lugano-Viganello, Switzerland
Interests: metal additive manufacturing; design for additive manufacturing; process optimization and engineering; functionally graded materials; high-entropy alloys
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Prof. Dr. Samuel Rey-Mermet

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Institute of Systems Engineering, School of Engineering, HES-SO Valais-Wallis, Rue de l’Industrie 23, Sion, Switzerland
Interests: additive manufacturing; powder metallurgy; shape memory alloys; functional materials
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Special Issue Information

Dear colleagues,

Over the past decade, metal additive manufacturing (AM) technologies have demonstrated to be fabrication processes enabling innovative engineering solutions which exhibit unprecedented performance advantages not achievable through more conventional manufacturing methods. AM metal structures and alloys, such as functionally graded materials, shape memory alloys and high-entropy alloys, fabricated exhibit innovative performance properties such as self-healing, excellent mechanical strength at high temperatures, shape memory effect, improved corrosion and wear resistance, and enhanced biocompatibility, increasing industrial impact in sectors such as aerospace, automotive, biomedical and power generation, outperforming the current engineering solutions.

This Special Issue will compile recent and innovative developments in the field of additive manufacturing of metal alloys and structures. The articles presented in this Special Issue will cover topics ranging from, but not limited to, AM high-entropy alloy optimisation and characterisation, AM functionally graded materials, AM advanced metals design and development, process and microstructural simulation, AM properties analysis and assessment, enabling advanced functionalities through metal AM techniques, among others. The topics are open to both basic and applied research with strong industrial interest, as well as for the development of applications.

Dr. Federico Mazzucato
Prof. Dr. Samuel Rey-Mermet
Guest Editors

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Keywords

metal additive manufacturing
high-entropy alloys
functionally graded materials
microstructure analysis
advanced functionalities
process simulation
process engineering
advanced metal alloys
mechanical properties

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Published Papers (11 papers)

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Research

11 pages, 4038 KB

Open AccessArticle

Effect of Laser Energy Density During LPBF on the Structure and Mechanical Properties of Al–15Sn–5Pb Alloy

by Nikolay M. Rusin, Alexander L. Skorentsev, Kirill O. Akimov, Vadim E. Likharev, Dmitry P. Il’yashchenko and Andrey I. Dmitriev

Materials 2025, 18(23), 5268; https://doi.org/10.3390/ma18235268 - 21 Nov 2025

Viewed by 443

Abstract

Al–15Sn–5Pb (vol.%) alloy was fabricated by the Laser Powder Bed Fusion (LPBF) method at laser scanning speeds of 0.8, 1.0, and 1.2 m/s and laser powers ranging from 70 to 130 W. The samples were synthesized from a mixture of elemental powders using an ONSINT AM150 3D printer under a flowing argon atmosphere. The structure and mechanical properties under compression tests of the produced material were investigated as a function of the volumetric laser energy density (E) during LPBF. It has been established that low laser energy density during LPBF results in incomplete melting of aluminum particles and a non-uniform distribution of soft inclusions within the material. Increasing the energy density ensures a significantly more uniform distribution of the phases, resulting in the formation of a fine-grained three-phase alloy. It was established that both the ductility and strength of the alloy improve with the increase in E until a critical value is reached. As a result, at E ≥ 48 J·mm⁻³, the ultimate strength of the alloy reaches 100 ± 5 MPa, and its deformation before fracture is 15 ± 1%. Substituting one quarter of the tin volume with lead results in a significant increase in the ductility of the LPBF-fabricated aluminum alloy. Full article

(This article belongs to the Special Issue Additive Manufacturing of Metals and Alloys: Microstructure and Mechanical Properties)

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19 pages, 7806 KB

Open AccessArticle

Investigation on the Microstructure and Mechanical Properties of X70 Pipeline Steel Fabricated by Laser-Directed Energy Deposition

by Zhandong Wang, Chunke Wang, Linzhong Wu and Guifang Sun

Materials 2025, 18(21), 4997; https://doi.org/10.3390/ma18214997 - 31 Oct 2025

Viewed by 494

Abstract

The laser-directed energy deposition (L-DED) technique, with its excellent environmental adaptability and superior repair capability, shows great potential for the repair of damaged X70 pipeline steel. In this work, the microstructure and mechanical properties of L-DED repaired X70 steel were systematically investigated. The deposited material exhibited inhomogeneity along the building direction. From the bottom to the top, the grains gradually coarsened, and the proportion of polygonal ferrite increased. This was mainly attributed to increasing thermal accumulation with deposition height, which reduced the cooling rate and promoted solid-state transformations at higher temperatures. Meanwhile, the heat accumulation and intrinsic heat treatment reduced the dislocation density and promoted Fe₃C precipitation within grains and along boundaries. Microhardness was highest in the bottom region and decreased along the building direction due to the gradual coarsening of microstructure and decreasing in dislocation density. The L-DED X70 showed lower yield strength (435 MPa) and ultimate tensile strength (513 MPa) compared to the base material and API 5L requirements. The elongation of the L-DED X70 was 42.9%, which was 58% higher than that of the base material, indicating excellent ductility. These results revealed a thermal history-dependent strength–ductility trade-off in the L-DED repaired X70 steel. Therefore, more efforts are needed to control the L-DED thermal process, tailor the microstructure, enhance strength, and meet the service requirements of harsh environments. Full article

(This article belongs to the Special Issue Additive Manufacturing of Metals and Alloys: Microstructure and Mechanical Properties)

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17 pages, 4695 KB

Open AccessArticle

Crack Arrest Effect of FeMnNiSi-Inconel625-Ni60 Laminated Structure Prepared by Laser Cladding Additive Manufacturing

by Lihong Ding, Weining Lei and Jufang Chen

Materials 2025, 18(21), 4996; https://doi.org/10.3390/ma18214996 - 31 Oct 2025

Viewed by 393

Abstract

This study addresses the technical challenges of cracking and surface crack initiation in Ni60 alloy cladding layers fabricated by laser cladding additive manufacturing on FeMnNiSi alloys. An innovative FeMnNiSi-Inconel625-Ni60 laminate design was proposed, achieving metallurgical bonding of the dissimilar materials through an Inconel625 transition layer. This effectively addresses the interfacial stress concentration issue caused by differences in thermal expansion coefficients in conventional processes. The results demonstrate that the interfacial microstructure is regulated by synergistic Nb-Mo element segregation, promoting the precipitation of γ″ phase and the formation of a nanoscale Laves phase. This phase not only inhibits carbide aggregation and growth, refining grain size, but also deflects crack propagation paths by pinning dislocations, achieving a dual mechanism of stress reduction and crack arrest. The Ni60 cladding layer in the laminated structure exhibits an average surface microhardness of 641.31 HV_0.3, 3.88 times that of the substrate (165.22 HV_0.3), while the Inconel625 base layer shows 340.71 HV_0.3, 2.06 times the substrate’s value. Wear testing reveals the laminated cladding layer has a wear volume of 0.086 mm³ (0.243 mm³ less than the substrate’s 0.329 mm³) and a wear rate of 0.86 × 10⁻² mm³/(N·m), 73.86% lower than the substrate’s 3.29 × 10⁻² mm³/(N·m), indicating superior wear resistance. The electrochemical test results show that under the same corrosion conditions, the self-corrosion potential and polarization resistance of the FeMnNiSi-Inconel625-Ni60 cladding layer are significantly higher than those of the substrate, while the corrosion current density is significantly lower than that of the substrate. The frequency stability region at the highest impedance modulus |Z| is wider than that of the substrate, and the corrosion rate is 71.86% slower than that of the substrate, demonstrating excellent wear resistance. This study not only reveals the mechanism by which Laves phases improve interfacial properties through microstructural regulation but also provides a scalable interface design strategy for heterogeneous material additive manufacturing, which has important engineering value in promoting the application of laser cladding technology in the field of high-end equipment repair. Full article

(This article belongs to the Special Issue Additive Manufacturing of Metals and Alloys: Microstructure and Mechanical Properties)

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19 pages, 8369 KB

Open AccessArticle

Influence of Laser Metal Deposition Process Parameters on the Structural Integrity of CuSn₁₁Bi₃ Coatings on C45

by Federico Mazzucato, Edouard Baer, Samuel Rey-Mermet and Anna Valente

Materials 2025, 18(18), 4368; https://doi.org/10.3390/ma18184368 - 18 Sep 2025

Viewed by 433

Abstract

Bronze-steel bimetallic structures are structural components finding a growing application in industrial sectors such as aerospace, power generation, and machinery. Recent legislation on green economy and sustainable manufacturing is boosting industry to implement innovative manufacturing processes and new metal alloys capable of lowering environmental footprint by avoiding toxic substances. Laser Metal Deposition is a cost-effective Additive Manufacturing technique for producing bimetallic components by limiting material waste and reducing energy consumption. In this research work, the influence of the main LMD process parameters on the final quality of CuSn₁₁Bi₃ coatings on C45 surfaces is analyzed. The Cu-based powder is specifically designed and developed to reduce environmental pollution and increase worker safety by avoiding the use of hazardous chemical elements. The performed observations demonstrate that high-density (99.90%) and crack-free clads are feasible by preventing melt pool dilution zones. Cu diffusion into the C45 substrate deteriorates the structural integrity at the clad-substrate interface by inducing liquid metal embrittlement cracking, whereas steel diffusion into the as-deposited clad promotes crack propagation. High-density (up to 99.97%) and crack-free CuSn₁₁Bi₃ coatings are achieved by using low specific energies (from 17 J/mm² to 40 J/mm²) and reducing the Oxygen content during sample manufacturing up to 0.02%. Full article

(This article belongs to the Special Issue Additive Manufacturing of Metals and Alloys: Microstructure and Mechanical Properties)

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13 pages, 12319 KB

Open AccessArticle

Effects of Homogenization Heat Treatment on Microstructure of Inconel 718 Lattice Structures Manufactured by Selective Laser Melting

by Lucia-Antoneta Chicos, Camil Lancea, Sebastian-Marian Zaharia, Grzegorz Cempura, Adam Kruk and Mihai Alin Pop

Materials 2025, 18(17), 4149; https://doi.org/10.3390/ma18174149 - 4 Sep 2025

Cited by 2 | Viewed by 1305

Abstract

Inconel 718 is a nickel-based superalloy that has a wide range of applications in the industries that require corrosion resistance or high-temperature resistance. It is well known that parts display internal stresses, anisotropy, and alloying element segregation after the selective laser melting (SLM) process. A homogenization heat treatment, which reduces internal stresses and homogenizes the material structure, can resolve these shortcomings. The present study focuses on the impact of this heat treatment on the microstructure of the Inconel 718 material produced by SLM. The research results indicate that this heat treatment improves both the material microstructure and mechanical performance by lessening the microstructural inhomogeneities, dissolving the Laves phases, and promoting grain coarsening. The findings of this study can contribute to the optimization of post-fabrication strategies for Inconel 718 parts fabricated by SLM. Full article

(This article belongs to the Special Issue Additive Manufacturing of Metals and Alloys: Microstructure and Mechanical Properties)

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20 pages, 5483 KB

Open AccessCommunication

Analysis of the Microstructure and Mechanical Properties of Austenitic Stainless Steel 310 Manufactured via WAAM

by Aline Cipriano, Célia de Fraga Malfatti, Henrique Cechinel Casagrande, Anderson Daleffe, Jovani Castelan and Pedro Henrique Menegaro Possamai

Materials 2025, 18(16), 3855; https://doi.org/10.3390/ma18163855 - 18 Aug 2025

Cited by 2 | Viewed by 1227

Abstract

The objective of this study was to characterize austenitic stainless steel 310 produced by Wire and Arc Additive Manufacturing (WAAM), addressing a gap in the literature regarding this alloy. Microstructural, chemical, and mechanical analyses were performed. Optical and electron microscopy revealed a predominantly columnar grain structure with characteristic tracks along the deposition direction. Point and mapping EDS analyses indicated a homogeneous distribution of iron, chromium, and nickel; however, point measurements suggested a possible underestimation of nickel, likely due to high relative error. Tensile tests demonstrated anisotropic mechanical behavior, with yield strength meeting standards at 45° and 90°, but lower at 0°. Ultimate tensile strength and elongation were below conventional requirements, with a maximum elongation of 15% at 90°. Additionally, the sample exhibited a total porosity of approximately 0.89%, which contributes to the reduction in mechanical properties, especially in the direction parallel to the deposition tracks. Overall, the WAAM-produced 310 stainless steel presented a microstructure similar to hot-rolled and annealed AISI 310 steel, but with distinctive features related to the additive process, such as mechanical anisotropy and microstructural directionality. These limitations highlight the need for process optimization to improve mechanical performance but reinforce the alloy’s structural potential in additive manufacturing. Full article

(This article belongs to the Special Issue Additive Manufacturing of Metals and Alloys: Microstructure and Mechanical Properties)

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23 pages, 5546 KB

Open AccessArticle

Evaluation of a Method for Determining Material Strength Based on Hardness Measurements: A Case Study of the Ti6Al4V Alloy

by Karolina Karolewska, Mateusz Wirwicki and Bogdan Ligaj

Materials 2025, 18(16), 3726; https://doi.org/10.3390/ma18163726 - 8 Aug 2025

Viewed by 781

Abstract

The aim of this study was to evaluate the feasibility of estimating the tensile strength of Ti6Al4V alloy, based on HV measurements. The investigation included samples that were manufactured using both additive technology and conventional methods, under various conditions: as-built, heat-treated, and untested mechanically. Static tensile tests and HV measurements were performed to assess the influence of the manufacturing method, heat treatment, and mechanical loading on material performance. The highest tensile strength was recorded for as-built samples, while the greatest ductility was observed in conventionally drawn bar samples. Hardness values generally correlated with tensile strength trends; however, in heat-treated specimens, the relationship between hardness and tensile strength was found to be nonlinear. Specimens that were not subjected to tensile testing exhibited higher HV values than their mechanically tested counterparts, indicating a potential effect of prior deformation on the local material condition. The results confirm that hardness testing can be a useful indirect method for estimating the tensile strength of Ti6Al4V, particularly in materials with controlled and uniform microstructures. For additively manufactured and heat-treated materials, however, the current empirical models may require adjustment or enhancement using advanced predictive approaches. The proposed indirect method offers an alternative to destructive testing, especially in the industrial quality control context for metal AM. Full article

(This article belongs to the Special Issue Additive Manufacturing of Metals and Alloys: Microstructure and Mechanical Properties)

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16 pages, 7807 KB

Open AccessArticle

Rapid-Optimized Process Parameters of 1080 Carbon Steel Additively Manufactured via Laser Powder Bed Fusion on High-Throughput Mechanical Property Testing

by Jianyu Feng, Meiling Jiang, Guoliang Huang, Xudong Wu and Ke Huang

Materials 2025, 18(15), 3705; https://doi.org/10.3390/ma18153705 - 6 Aug 2025

Viewed by 742

Abstract

To ensure the sustainability of alloy-based strategies, both compositional design and processing routes must be simplified. Metal additive manufacturing (AM), with its exceptionally rapid, non-equilibrium solidification, offers a unique platform to produce tailored microstructures in simple alloys that deliver superior mechanical properties. In this study, we employ laser powder bed fusion (LPBF) to fabricate 1080 plain carbon steel, a binary alloy comprising only iron and carbon. Deviating from conventional process optimization focusing primarily on density, we optimize LPBF parameters for mechanical performance. We systematically varied key parameters (laser power and scan speed) to produce batches of tensile specimens, which were then evaluated on a high-throughput mechanical testing platform (HTP). Using response surface methodology (RSM), we developed predictive models correlating these parameters with yield strength (YS) and elongation. The RSM models identified optimal and suboptimal parameter sets. Specimens printed under the predicted optimal conditions achieved YS of 1543.5 MPa and elongation of 7.58%, closely matching RSM predictions (1595.3 MPa and 8.32%) with deviations of −3.25% and −8.89% for YS and elongation, respectively, thus validating model accuracy. Comprehensive microstructural characterization, including metallographic analysis and fracture surface examination, revealed the microstructural origins of performance differences and the underlying strengthening mechanisms. This methodology enables rapid evaluation and optimization of LPBF parameters for 1080 carbon steel and can be generalized as an efficient framework for robust LPBF process development. Full article

(This article belongs to the Special Issue Additive Manufacturing of Metals and Alloys: Microstructure and Mechanical Properties)

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18 pages, 4216 KB

Open AccessArticle

On the Prediction and Optimisation of Processing Parameters in Directed Energy Deposition of SS316L via Finite Element Simulation and Machine Learning

by Mehran Ghasempour-Mouziraji, Daniel Afonso and Ricardo Alves de Sousa

Materials 2025, 18(5), 1039; https://doi.org/10.3390/ma18051039 - 26 Feb 2025

Cited by 4 | Viewed by 1178

Abstract

In the current study, the integration of finite element simulation and machine learning is used to find the optimal combination of processing parameters in the directed energy deposition of SS316L. To achieve this, the FE simulation was validated against previously implemented research, and a series of simulations were conducted. Three inputs, namely laser power, scanning speed, and laser beam radius, and two outputs, namely residual stress and displacement, were considered. To run the machine learning model, artificial neural networks and a non-dominated sorting genetic algorithm were applied to determine the optimal combination of processing parameters. In addition, the current study underscores the novelty of combining FE simulation and machine learning methods, which provides enhanced precision and efficiency in controlling residual stress and displacement (geometrical deviation) in the Directed Energy Deposition (DED) process. Then, the results obtained via machine learning were validated with confirmatory tests and reported. The findings offer a practical solution for process parameter optimization, contributing to the progression of additive manufacturing technologies. Full article

(This article belongs to the Special Issue Additive Manufacturing of Metals and Alloys: Microstructure and Mechanical Properties)

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14 pages, 11262 KB

Open AccessArticle

Effect of Co Addition on the Microstructure and Mechanical Properties of Sn-11Sb-6Cu Babbitt Alloy

by Zhan Cheng, Meng Wang, Bo Wang, Lei Zhang, Ting Zhu, Ningbo Li, Jifa Zhou and Fei Jia

Materials 2024, 17(22), 5494; https://doi.org/10.3390/ma17225494 - 11 Nov 2024

Cited by 3 | Viewed by 1521

Abstract

A Babbitt alloy SnSb11Cu6 with 0–2.0 wt.% Co was synthesized using the induction melting process. This study examined the effect of cobalt (Co) on the microstructure, tensile properties, compressive properties, Brinell hardness, and wear properties of SnSb11Cu6 using optical microscopy (OM), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), a universal tensile testing machine, a Brinell hardness tester, and a wear testing machine. The results indicate that the optimal quantity of Co can enhance the microstructure of the Babbitt alloy and promote microstructure uniformity, with presence of Co₃Sn₂ in the matrix. With the increase in Co content, the tensile and compressive strength of the Babbitt alloy first increased and then decreased, and the Brinell hardness gradually increased with the increase in Co content. The presence of trace Co has a minimal effect on the dry friction coefficient of the Babbitt alloy. When the Co content exceeds 1.5 wt.%, the friction properties of the Babbitt alloy deteriorate significantly. The optimized Babbitt alloy SnSb11Cu6-1.5Co was subsequently fabricated into wires, followed by conducting cold metal transfer (CMT) surfacing experiments. The Co element can promote the growth of interfacial compounds. The microstructure at the interface of the Babbitt alloy/steel is dense, and there is element diffusion between it. The metallurgical bonding is good, and there are serrated compounds relying on the diffusion layer to extend to the direction of the additive layer with serrated compounds extending and growing from the diffusion layer to the additive layer. Overall, Babbitt alloys such as SnSb11Cu6 exhibit improved comprehensive properties when containing 1.5 wt.% Co. Full article

(This article belongs to the Special Issue Additive Manufacturing of Metals and Alloys: Microstructure and Mechanical Properties)

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13 pages, 5820 KB

Open AccessArticle

Effect of Laser Parameters on Fracture Properties of Laser-Repaired Cracks with Micro/NanoMaterial Addition: Multiscale Analysis

by Yinyin Li, Wei Jiang and Meiqiu Li

Materials 2024, 17(18), 4656; https://doi.org/10.3390/ma17184656 - 23 Sep 2024

Viewed by 1199

Abstract

In laser crack repair processes, laser parameters have significant influence on repair quality. Improper combination of laser process parameters may result in defects—such as porosity, ablation, and coarse grain size—in remelted zones. A trans-scale computational model is established by combining crystal plasticity finite elements and variable-node finite elements. The influence of microstructure characteristics such as grain size and porosity of the repair layer on the cumulative plastic slip (CPS) on the dominant slip system at the meso-scale and the J-integral at the macro-scale is studied to explore the effect of laser process parameters on repair quality. The results show that when the laser power is 1800 W and the heating time is 0.5 s, the grain size and porosity of the repaired specimen are the smallest. The J-integral of the repaired specimen is more than 8% smaller than that of the unrepaired specimen and about 3% smaller than that of the repaired specimen, with a laser power of 2000 W and a heating time of 1 s. Pores increase the CPS of the crystal around the pores, especially when a pore have sharp corners. Selecting appropriate laser process parameters can not only refine grain size but also reduce the volume fraction of pores and thus reduce the J-integral and eventually improve repair quality of repaired specimens. The study investigates the relationship of process parameter–microstructure–repair quality in the laser repair process and provides a method for studying the mechanical behavior of materials at macro and micro scales. Full article

(This article belongs to the Special Issue Additive Manufacturing of Metals and Alloys: Microstructure and Mechanical Properties)

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