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Welding, Joining, and Additive Manufacturing of Metals and Alloys (Third Edition)

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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 March 2026) | Viewed by 7246

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Dr. Damjan Klobcar

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Faculty of Mechanical Engineering, University of Ljubljana, Aškerčeva 6, 1000 Ljubljana, Slovenia
Interests: additive manufacturing; characterisation of weld joints; ultrasonic welding; laser welding; friction stir welding; friction welding; resistance spot welding; arc welding technologies; adhesive bonding; vibration assisted welding and additive manufacturing; thermal and mechanical post-processing
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Dr. Drago Bračun

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Laboratory for Mechatronics, Production Systems and Automation, Faculty of Mechanical Engineering, University of Ljubljana, Ljubljana, Slovenia
Interests: vision systems for industrial quality inspection; automation; process monitoring and improvement; AI
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Dr. Tomaž Vuherer

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Laboratory for Welding, Faculty of Mechanical Engineering, University of Maribor, Maribor, Slovenia
Interests: characterisation of weld joints; instrumented charpy test; fatique; fracture mechanics of the weld joints; fatigue crack growth test; friction stir welding; friction welding; resistance spot welding; arc welding technologies; residual stress
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Special Issue Information

Dear Colleagues,

The constant development of new materials and products also promotes the research and development of welding, joining, and build-up welding technologies, as well as additive manufacturing technologies. These investigations are multidisciplinary and encompass processes and their automation, monitoring and control, materials, weldability and joinability of materials and alloys, product and joint design, and advanced characterization and numerical simulations to comprehensively understand physical and metallurgical phenomena. A successful understanding of these phenomena enables the development of solutions to overcome these problems. This Special Issue aims to report the results of basic and applied research, as well as case studies, in the fields of weldability and joinability of materials, additive manufacturing, automation, process improvement, and advanced characterization.

The potential topics for the Special Issues include, but are not limited to, the following:

Micro and nano joining.

Diffusion bonding.

Adhesive bonding.

Hybrid welding and additive manufacturing.

Laser welding.

Welding with mechanical energy.

Weldability of similar and dissimilar materials.

Advanced material characterization.

Residual stress and distortion.

Numerical modeling and simulation.

Additive manufacturing processes (DED, powder bead fusion, binder jetting, etc.).

Additive manufacturing of new materials, multi-materials, and functionally graded materials.

Improvement in materials using weld surfacing and additive manufacturing.

Repair welding and repair additive manufacturing of products.

In situ processing and post-processing in additive manufacturing or welding.

Advanced material characterization.

Fatigue of joints and AM parts.

Destructive and non-destructive testing of joints and AM parts.

Process automation, monitoring, and control.

Monitoring systems, vision, automation, and quality inspection.

Application of Artificial Intelligence in process planning, monitoring and control.

Dr. Damjan Klobcar
Dr. Drago Bračun
Dr. Tomaž Vuherer
Guest Editors

Manuscript Submission Information

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 250 words) can be sent to the Editorial Office for assessment.

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. Materials is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

welding and joining technologies
brazing and soldering
additive manufacturing
adhesive bonding
weldability of materials

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Related Special Issue

Welding, Joining, and Additive Manufacturing of Metals and Alloys (Second Edition) in Materials (10 articles)

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Research

24 pages, 15635 KB

Open AccessArticle

Effect of Post-Printing Methods on the Microstructure and Mechanical Properties of Ti6Al4V Titanium Alloy Samples Fabricated Using Laser Powder Bed Fusion

by Krzysztof Żaba, Stanislav Rusz, Alicja Haslik-Sopata, Łukasz Kuczek, Ilona Różycka, Maciej Balcerzak and Tomasz Trzepieciński

Materials 2026, 19(2), 401; https://doi.org/10.3390/ma19020401 - 19 Jan 2026

Viewed by 611

Abstract

Laser powder bead fusion (LPBF) allows for the fabrication of highly accurate components from metal powders, which is difficult to achieve using traditional methods. LPBF-produced components can be characterized by their porosity and unfavorable microstructure, making further processing difficult. Therefore, appropriate post-printing methods are crucial, as they reduce porosity, reduce residual stresses, and stabilize the microstructure. The aim of this paper was to determine the effect of post-printing methods on the microhardness and microstructure of Ti6Al4V titanium alloy samples fabricated using the LPBF process in different orientations. Hot isostatic pressing (HIP) at various temperatures (910 °C, 1150 °C, 1250 °C), annealing at 1020 °C, and twist channel angular pressing using a 90° channel ending with a helical exit were considered postprocessing methods for LPBF-produced samples. Printing orientation significantly determined the effectiveness of HIP and the heat treatment processes. Higher microhardness was observed on the cross-section oriented perpendicular to the 3D printing direction. Annealing under appropriately selected conditions favors the precipitation of fine particles of the α phase in the β phase, leading to a strengthening effect by precipitation. Based on the microhardness measurements, clear differences were observed in the mean values, statistical ranges, and result distributions depending on the printing plane, HIP process parameters, and the use of an additional heat treatment. The HIP process leads to a more pronounced homogenization of microstructure and defect reduction, with the morphology of the microstructure and microhardness distribution dependent on the HIP process temperature. Full article

(This article belongs to the Special Issue Welding, Joining, and Additive Manufacturing of Metals and Alloys (Third Edition))

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22 pages, 8601 KB

Open AccessArticle

Influence of Twist Channel Angular Pressing Process on Microhardness and Microstructural Behavior of Explosively Welded Al/Cu Plates

by Krzysztof Żaba, Łukasz Kuczek, Ilona Różycka, Ondřej Hilšer, Tomasz Trzepieciński and Kinga Ortyl

Materials 2026, 19(2), 302; https://doi.org/10.3390/ma19020302 - 12 Jan 2026

Viewed by 332

Abstract

Due to their unique properties resulting from the combination of metals with different properties, bimetallic sheets are desirable in the energy, petrochemical, and shipbuilding industries. In this article, explosively welded EN AW-1050/Cu-ETP (Al/Cu) plates were used as the test material. One of the greatest advantages of Al/Cu bimetallic plates is their high deformability, which allows for easy plastic forming. The aim of this study was to determine the effect of severe plastic deformation on the microstructure and microhardness of explosively welded EN AW-1050/Cu-ETP plates. Bimetallic samples were processed using the Twist Channel Angular Pressing (TCAP) process. This process consisted of varying the number of passes and the sample orientation relative to the helical exit channel of the TCAP die. For comparative purposes, a microstructural analysis and the microhardness testing of the as-welded samples were also carried out. Microstructural analysis of TCAP-processed samples showed that the sample deformed along route Bc exhibited the most deformed weld interface profile. No cracking or delamination was observed in the Al/Cu interfacial transition layer of TCAP-processed samples. The number of passes and orientation of the bimetallic material relative to the die exit channel affected the final microhardness in the individual layers of explosively welded EN AW-1050/Cu-ETP bimetallic plate. Full article

(This article belongs to the Special Issue Welding, Joining, and Additive Manufacturing of Metals and Alloys (Third Edition))

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12 pages, 1441 KB

Open AccessArticle

Impact of Substrate Preheating on Weld Quality, Microstructure, Corrosion Resistance, and Mechanical Properties in Gas Tungsten Arc Welding of UNS S32750 Super Duplex Stainless Steel

by Eli Jorge da Cruz Junior, Raul Henrique Ribeiro, Francisco Mateus Faria de Almeida Varasquim, Fábio Oliveira Carvalho, Luiz Fernando Frezzatti Santiago, Gabriela Pereira Lemos, Vicente Afonso Ventrella and Irene Calliari

Materials 2026, 19(2), 221; https://doi.org/10.3390/ma19020221 - 6 Jan 2026

Viewed by 414

Abstract

Super duplex stainless steels (SDSS) are materials known for their exceptional mechanical strength and high resistance to corrosion due to their dual- phase microstructure consisting of ferrite and austenite in roughly equal proportions. However, the Gas Tungsten Arc Welding (GTAW) process used to join SDSS often causes microstructural imbalances, mainly ferritic structures, or the formation of harmful intermetallic phases, which can weaken the material’ s desirable properties. This study examines the effect of substrate preheating on the microstructure, mechanical properties, and corrosion resistance of UNS S32750 SDSS welds produced by GTAW. Preheating the substrate was considered as a strategy to improve phase balance in the fusion zone by extending the time within the ferrite- to- austenite transformation temperature range, thus slowing the cooling rates. Four conditions were tested: welding at room temperature (RT) and preheating to 100 °C (T100), 200 °C (T200), and 300 °C (T300). Welding parameters remained constant. The fusion zone microstructure was analyzed using metallographic techniques, while mechanical properties were evaluated through microhardness tests. Corrosion resistance was assessed with potential dynamic polarization in a 3.5% NaCl solution. The results showed significant improvements in microstructural balance with higher preheating temperatures. The austenite volume fraction in the fusion zone increased from about 16% at RT to 42% at T 300. Mechanical testing indicated a decrease in microhardness from 341 HV at RT to 314 HV at T 300, reflecting the increased austenite content and its associated toughness. Corrosion tests demonstrated enhanced resistance under preheated conditions, with T 300 exhibiting the highest corrosion potential and the lowest corrosion current, nearing the performance of the base metal. These findings suggest that preheating is a practical, cost- effective method for optimizing the GTAW process for SDSS, eliminating the need for expensive filler materials and stabilizing the microstructure elements. Full article

(This article belongs to the Special Issue Welding, Joining, and Additive Manufacturing of Metals and Alloys (Third Edition))

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24 pages, 6273 KB

Open AccessEditor’s ChoiceArticle

Influence of Post-Processing on S-Phase Formation During Plasma Nitriding of Additively Manufactured Inconel 939

by Piotr Maj, Joanna Radziejewska, Ryszard Diduszko, Michał Marczak, Rafał Nowicki, Podolak-Lejtas Anna, Tomasz Borowski and Ryszard Sitek

Materials 2026, 19(1), 130; https://doi.org/10.3390/ma19010130 - 30 Dec 2025

Viewed by 500

Abstract

Active screen plasma nitriding (ASPN) of additively manufactured nickel-based superalloys represents an understudied surface enhancement pathway. This study presents the first systematic investigation of ASPN applied to additively manufactured Inconel 939 (IN 939), evaluating four distinct post-processing routes combining heat treatment atmospheres (argon versus air cooling), vibratory finishing, and lapping under identical nitriding parameters (450 °C, 8 h, 25% N₂ + 75% H₂, 3 hPa). Contrasting nitriding behaviours emerged as a function of the post-processing route: the air-cooled thermal treatment (HT-air-vibr-lap) promotes formation of a thick Al/Cr-rich oxide layer (10–15 µm) that substantially inhibits nitrogen diffusion, resulting in thin and discontinuous nitrided layers. Conversely, the inert atmosphere route (HT-Ar-vibr-lap) circumvents oxide formation, enabling continuous S-phase (expanded austenite, γN) layer development of a 6.4 ± 0.3 µm thickness with exceptional surface hardness (~1200 HV, representing 3–4× enhancement relative to base material). X-ray diffraction confirmed S-phase formation with refined lattice parameter (3.609 Å) and secondary nitride phases (CrN-type and NbN/TaN-type precipitates). The post-processing sequence—particularly heat treatment atmosphere and mechanical finishing methodology—emerged as a critical controlling parameter for S-phase formation efficiency and mechanical properties of nitrided layers in additively manufactured nickel-based superalloys. This work addresses a knowledge gap distinct from the existing literature on conventional Inconel systems, establishing that controlled surface modification through post-processing can achieve the required properties. Full article

(This article belongs to the Special Issue Welding, Joining, and Additive Manufacturing of Metals and Alloys (Third Edition))

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26 pages, 20340 KB

Open AccessArticle

Laser Power-Dependent Microstructural Evolution and Fracture Mechanisms in Ti80 Titanium Alloy Welds: A Multi-Scale Investigation

by Chuanbo Zheng, Zhanwen Yang, Guo Yi, Liuyu Zhang, Xiaomeng Zhou and Xinyu Yao

Materials 2026, 19(1), 116; https://doi.org/10.3390/ma19010116 - 29 Dec 2025

Viewed by 456

Abstract

The laser welding of 4 mm thick Ti80 alloy under different powers was analyzed, and the weld morphology, microstructure, and mechanical properties were studied. A simulation model was established based on ABAQUS, and laser welding simulations were conducted using 2520 W and 3000 W laser welding power sources to analyze the temperature field and stress field, which were verified by experiments. The increase in power changed the weld morphology from Y-shaped to X-shaped and affected the number of pores in incomplete and complete penetration. The microstructure in the weld zone presented fine acicular α′ phase. Subsequently, grain boundary distribution maps, Kernel Average Misorientation (KAM) maps, and geometrically necessary dislocation (GND) density maps were generated through electron backscatter diffraction (EBSD) analysis. These comprehensive data visualizations enabled multi-dimensional investigation, establishing and analyzing correlations between laser welding parameters, microstructural evolution, and mechanical properties in Ti80 titanium laser welding. The hardness of the base material was 320 HV to 360 HV, and it increased from 420 HV to 460 HV in the weld zone. At 3000 W, the tensile strength reached 903.12 MPa, and the elongation was 10.40%, indicating ductile fracture. The simulation results accurately predicted the maximum longitudinal residual stress in the weld zone, with an error of 1.65% to 1.81% of the measured value. Full article

(This article belongs to the Special Issue Welding, Joining, and Additive Manufacturing of Metals and Alloys (Third Edition))

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19 pages, 9405 KB

Open AccessArticle

Effect of Build-Up Strategy and Selective Laser Melting Process Parameters on Microstructure and Mechanical Properties of 316L Stainless Steel

by Krzysztof Żaba, Maciej Balcerzak, Paweł Pałka, Radek Čada, Tomasz Trzepieciński and Martyna Szczepańska

Materials 2026, 19(1), 26; https://doi.org/10.3390/ma19010026 - 20 Dec 2025

Viewed by 888

Abstract

Additive manufacturing, or 3D printing, is a method for creating three-dimensional objects layer-by-layer based on a digital model. This article presents the results of research on selective laser melting (SLM) of 316L stainless steel powder. Its aim is to investigate the relation between the mechanical properties of SLM-fabricated 316L steel samples obtained from uniaxial tensile tests and the SLM process parameters including the build-up strategy. Four different configurations of 3D printing orientation relative to the build platform were considered. The variable parameters of the SLM process were laser power and laser scanning speed. The morphology of the external surfaces and the microstructure of the SLM-processed samples were examined. The results show that samples printed in the longitudinal and transverse configurations had the highest tensile strength. Samples printed in the vertical and diagonal configurations had the greatest dispersion of values of mechanical parameters. The main difference in mechanical properties after doubling the SLM process parameters was a decrease in elongation for samples printed in the longitudinal configuration and an increase in this value for samples printed in the transverse configuration. The use of higher laser powers and laser scanning speeds guarantees a more compact, non-porous microstructure of SLM-processed samples. Full article

(This article belongs to the Special Issue Welding, Joining, and Additive Manufacturing of Metals and Alloys (Third Edition))

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16 pages, 9578 KB

Open AccessEditor’s ChoiceArticle

Effect of Molybdenum on Microstructural Evolution and High Cycle Fatigue Properties of Ti-xMo-2Fe Alloys

by HyoWoon Hwang and Dong-Geun Lee

Materials 2026, 19(1), 10; https://doi.org/10.3390/ma19010010 - 19 Dec 2025

Viewed by 541

Abstract

Ti-xMo-2Fe alloys with high specific strength were designed by adding Mo and Fe as β-stabilizing elements. The influence of cold swaging on the martensitic transformations in Ti-xMo-2Fe (x = 3.4, 5, 9.2 wt.%) alloys was investigated. In these alloys, appropriate chemical compositions promote a stress-induced phase transformation from the β phase to orthorhombic α″ martensite, which improves elongation while maintaining high strength. As the Mo content increases from 3.4 to 5 wt.%, the amount of β-stabilizing elements increases and the β stability is enhanced, thereby altering the phase transformation mechanism. In the Ti-9.2Mo-2Fe alloy, both α″ martensite and a very hard ω phase were identified by X-ray diffraction and transmission electron microscopy. The hard and brittle ω phase causes premature brittle fracture prior to macroscopic yielding. Among the investigated alloys, the Ti-5Mo-2Fe alloy exhibits the best overall combination of high tensile strength, elongation to failure, and high fatigue strength. Full article

(This article belongs to the Special Issue Welding, Joining, and Additive Manufacturing of Metals and Alloys (Third Edition))

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29 pages, 20387 KB

Open AccessArticle

Effects of Equal Channel Angular Pressing on the Microstructure and Mechanical Properties of Explosion-Welded Al-Cu Bimetallic Plates

by Krzysztof Żaba, Kinga Ortyl, Ondřej Hilšer, Martin Pastrnak, Łukasz Kuczek, Ilona Różycka, Paweł Pałka, Aleksander Gałka and Tomasz Trzepieciński

Materials 2025, 18(22), 5080; https://doi.org/10.3390/ma18225080 - 8 Nov 2025

Cited by 1 | Viewed by 816

Abstract

Explosive welding technology is crucial for the production of large-area plates composed of materials with varying plastic and physical properties. Severe plastic deformation processes increase the mechanical strength of the plates by refining grains and increasing dislocation density. The aim of the research presented in this paper was to analyze the effect of Equal Channel Angular Pressing (ECAP) on the mechanical properties and microstructure of an Al/Cu (EN AW-1050/Cu-ETP) bimetallic plate produced by the explosive welding technology. The ECAP process was carried out at room temperature. The ECAP experiments consisted of 1–3 passes using a die with a channel angle of 90°. The ram speed was 40 mm/min. The study also considered various sample cutting orientations (longitudinal, transverse) and various positions of the bimetallic sample in the die entry channel. Rotating the sample by an angle of 180° between consecutive passes was also considered. To achieve the research objective, static tensile tests, Vickers hardness tests at a load of 4.9 N, and microstructural analysis of the samples using scanning electron microscopy and energy dispersive spectroscopy were carried out. It was found that each subsequent pass in the ECAP process led to a gradual, severe change in the morphology of the Al/Cu interfacial transition layer. The orientation of the cutting plane of the samples was shown to have no effect on the hardness of the bimetallic material. Vickers hardness tests preceded by the ECAP process revealed a more uniform hardness distribution compared to the base material. The orientation of the Al/Cu plate layers in the ECAP die channel clearly influenced the character of the hardness distribution. Full article

(This article belongs to the Special Issue Welding, Joining, and Additive Manufacturing of Metals and Alloys (Third Edition))

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9 pages, 5251 KB

Open AccessCommunication

Electrochemical Surface Modification of Laser Cladded Ni-Based Single Crystal Superalloy in NaNO₃ Solution

by Jingbo Liu, Yongxin Liu, Xianqi Meng, Linfeng Tang, Xiaowei Lei and Nan Wang

Materials 2025, 18(21), 4967; https://doi.org/10.3390/ma18214967 - 30 Oct 2025

Viewed by 631

Abstract

Since mechanical processing can introduce stress in the sample, electrochemical dissolution has been utilized to attain shape accuracy in certain materials. However, this technique is rarely applied to laser-repaired Ni-based single-crystal superalloys. In this work, the transpassive dissolution behaviors of an additive manufacturing-repaired Ni-based single crystal superalloy in a 10% NaNO₃ solution were investigated by comparison with the substrate. A significant disparity in dissolution rates was found between the dendritic and interdendritic regions of the substrate, resulting in a rough surface. Conversely, the dissolution of the dendritic and interdendritic regions in the cladding structure occurred nearly simultaneously, leading to a high-quality, smooth surface. This behavior was attributed to the differences in phase dissolution preferences between the substrate and the cladding structure. It indicates that electrochemical dissolution is a promising method for achieving shape accuracy in laser-clad Ni-based single-crystal superalloys. Full article

(This article belongs to the Special Issue Welding, Joining, and Additive Manufacturing of Metals and Alloys (Third Edition))

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21 pages, 9175 KB

Open AccessArticle

Optimizing Welding Sequence and Improving Welding Process for Marine Thick-Walled Circular Pipes

by Tao Ma, Mingguan Fan, Haipeng Miao, Wei Shang and Mingxin Yuan

Materials 2025, 18(17), 4128; https://doi.org/10.3390/ma18174128 - 2 Sep 2025

Cited by 1 | Viewed by 1449

Abstract

To reduce welding deformation during the automated welding of thick-walled pipes in shipbuilding and thereby improve welding quality, a segmented multi-layer multi-pass welding sequence optimization and process improvement strategy is proposed. Firstly, based on a welding model for thick-walled pipes, a multi-layer multi-pass welding trajectory equation is established. A double-ellipsoidal moving heat source is adopted to design a circular multi-layer multi-pass double-ellipsoidal heat source model. Secondly, three circular pipe workpieces with different wall thicknesses are selected, and four segmented welding sequences are simulated using welding finite element analysis (FEA). Finally, based on the optimal segmented welding sequence, the welding process is improved, and optimal welding process parameters are determined based on deformation and residual stress analysis. The results of the segmented multi-layer multi-pass welding sequence optimization show that the skip-symmetric welding method yields the best results for thick-walled circular pipes. Compared to other welding sequences, it reduces welding deformation by an average of 6.50% and welding stress by an average of 5.37%. In addition, process improvement tests under the optimal welding sequence indicate that the best welding quality is achieved under the following conditions: for 10 mm thick pipes—200 A current, 24 V voltage, and 11.5 mm/s welding speed; for 15 mm thick pipes—215 A, 24.6 V, and 10 mm/s; and for 20 mm thick pipes—225 A, 25 V, and 11 mm/s. Full article

(This article belongs to the Special Issue Welding, Joining, and Additive Manufacturing of Metals and Alloys (Third Edition))

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