Welding and Joining of Metallic Materials: Microstructure and Mechanical Properties

A special issue of Crystals (ISSN 2073-4352). This special issue belongs to the section "Crystalline Metals and Alloys".

Deadline for manuscript submissions: 20 August 2024 | Viewed by 8652

Special Issue Editors


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Guest Editor
1. Institute of Science and Innovation in Mechanical and Industrial Engineering (INEGI), Rua Dr. Roberto Frias, 4200-465 Porto, Portugal
2. Department of Materials Engineering and Metallurgy, Faculty of Engineering, Arak University, Arak 38156-8-8349, Iran
Interests: welding metallurgy; simulation of welding; friction stir welding; welding of dissimilar materials; adhesive bonding; advanced joining processes

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Faculty of Arts, Science and Technology, University of Northampton, Northampton NN1 5PH, UK
Interests: laser materials processing; additive manufacturing; welding; design of experiments (DOE)
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CEMMPRE, Department of Mechanical Engineering, University of Coimbra, Polo II, Pinhal de Marrocos, 3030-788 Coimbra, Portugal
Interests: modeling and simulation of mechanical behavior of metallic materials; finite element simulation of friction stir welding process; artificial intelligence; multi-scale materials characterization
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Welding and joining metallic materials are vital in the aerospace, automotive, and construction industries to create complex assemblies and components. The quality and efficacy of welded joints hinge not only upon utilizing the appropriate joining techniques, but also upon the microstructure and mechanical properties of the resulting welds. It is of paramount importance to gain an insight into the relationship between the microstructural, mechanical, and joining process parameters, joint integrity, the overall performance of welded structures, and streamline fabrication practices.

This Special Issue invites researchers from academia, industry, and research institutions to contribute perspectives, original research articles, and reviews on welding and joining of metallic materials. This Special Issue aims to bring together a diverse collection of contributions to advance our understanding of welding and joining processes, foster innovation, and facilitate the development of optimized welding practices with improved microstructure and mechanical properties.

Dr. Reza Beygi
Dr. Mahmoud Moradi
Prof. Dr. Ali Khalfallah
Guest Editors

Manuscript Submission Information

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Keywords

  • friction stir welding
  • laser welding
  • electron beam welding
  • hybrid welding
  • adhesive bonding
  • welding-based additive manufacturing (WAAM)
  • gas metal arc welding (GMAW)
  • gas tungsten arc welding (GTAW)
  • shielded metal arc welding (SMAW)
  • welding parameters and optimization
  • microstructure
  • post-weld heat treatment
  • grain structure
  • phase transformations
  • precipitates
  • defects
  • residual stresses
  • mechanical properties
  • non-destructive testing
  • fatigue analysis
  • fracture mechanics
  • weld integrity
  • reliability assessments

Published Papers (9 papers)

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Research

22 pages, 5712 KiB  
Article
Study of the Microstructure and Mechanical Property Relationships of Gas Metal Arc Welded Dissimilar Protection 600T, DP450 and S275JR Steel Joints
by Mustafa Elmas, Oğuz Koçar and Nergizhan Anaç
Crystals 2024, 14(5), 477; https://doi.org/10.3390/cryst14050477 - 19 May 2024
Viewed by 466
Abstract
The need for combining dissimilar materials is steadily increasing in the manufacturing industry, and the resulting products are expected to always have high performance. While there are various methods available for joining such material pairs, one of the commonly preferred techniques is fusion [...] Read more.
The need for combining dissimilar materials is steadily increasing in the manufacturing industry, and the resulting products are expected to always have high performance. While there are various methods available for joining such material pairs, one of the commonly preferred techniques is fusion welding. In this study, three different steel materials (Protection 600T, DP450, and S275JR) were joined using gas metal arc welding (GMAW) in different combinations (similar/dissimilar). The microstructure and mechanical properties of the joints were evaluated. Tensile test, Vickers microhardness (HV 0.1), bending, Charpy V-notch impact testing, and microstructure examinations were conducted to analyze the weld and heat-affected zone. The tensile strengths of the base metal materials Protection 600T, DP450, and S275JR were found to be 1524.73 ± 18.7, 500.8 ± 10.4, and 508.5 ± 9.5 MPa, respectively. In welded samples of similar materials, the highest efficiency was found to be 103.05% for DP450/DP450, while in dissimilar welded joints, it was 105.5% for the DP450/S275JR pair. Hardness values for the base materials Protection 600T, DP450, and S275JR were measured as 526.5 ± 10.5, 153.8 ± 1.8, and 162.5 ± 5.2, respectively. In all welded samples, there was an increase in hardness in the weld zone (due to the welding wire) and the heat-affected zone (due to grain size refinement). While the impact energy values of similar material pairs were close to the base material impact energy values, the impact energy values of dissimilar material pairs varied according to the base materials. In addition, in joints made with similar materials, the bending force was close to the base materials, while a decrease in bending force was observed in joints formed with dissimilar materials. As a result, the welding of DP450 and S275JR materials was carried out efficiently. Protection 600T was welded with other materials, but its welding strength was limited to the strength of the material with low mechanical properties. Full article
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10 pages, 3851 KiB  
Article
Microstructural Optimization of Sn-58Bi Low-Temperature Solder Fabricated by Intense Pulsed Light (IPL) Irradiation
by Hyeri Go, Taejoon Noh, Seung-Boo Jung and Yoonchul Sohn
Crystals 2024, 14(5), 465; https://doi.org/10.3390/cryst14050465 - 16 May 2024
Viewed by 435
Abstract
In this study, intense pulsed light (IPL) soldering was employed on Sn-58Bi solder pastes with two distinct particle sizes (T3: 25–45 μm and T9: 1–8 μm) to investigate the correlation between the solder microstructure and mechanical properties as a function of IPL irradiation [...] Read more.
In this study, intense pulsed light (IPL) soldering was employed on Sn-58Bi solder pastes with two distinct particle sizes (T3: 25–45 μm and T9: 1–8 μm) to investigate the correlation between the solder microstructure and mechanical properties as a function of IPL irradiation times. During IPL soldering, a gradual transition from an immature to a refined to a coarsened microstructure was observed in the solder, impacting its mechanical strength (hardness), which initially exhibited a slight increase followed by a subsequent decrease. It is noted that hardness measurements taken during the immature stage may exhibit slight deviations from the Hall–Petch relationship. Experimental findings revealed that as the number of IPL irradiation sessions increased, solder particles progressively coalesced, forming a unified mass after 30 sessions. Subsequently, after 30–40 IPL sessions, notable voids were observed within the T3 solder, while fewer voids were detected at the T9-ENIG interface. Following IPL soldering, a thin layered structure of Ni3Sn4 intermetallic compound (IMC) was observed at the Sn-58Bi/ENIG interface. In contrast, reflow soldering resulted in the abundant formation of rod-shaped Ni3Sn4 IMCs not only at the reaction interface but also within the solder bulk, accompanied by the notable presence of a P-rich layer beneath the IMC. Full article
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32 pages, 19299 KiB  
Article
Effect of Exothermic Additions in Core Filler on Arc Stability and Microstructure during Self-Shielded, Flux-Cored Arc Welding
by Vasyl Lozynskyi, Bohdan Trembach, Egidijus Katinas, Kostiantyn Sadovyi, Michal Krbata, Oleksii Balenko, Ihor Krasnoshapka, Olena Rebrova, Sergey Knyazev, Oleksii Kabatskyi, Hanna Kniazieva and Liubomyr Ropyak
Crystals 2024, 14(4), 335; https://doi.org/10.3390/cryst14040335 - 31 Mar 2024
Viewed by 792
Abstract
In the conditions of an energy crisis, an important issue is the increase in energy efficiency and productivity of welding and hardfacing processes. The article substantiates the perspective of using exothermic additives introduced into core filler for flux-cored wire arc welding processes as [...] Read more.
In the conditions of an energy crisis, an important issue is the increase in energy efficiency and productivity of welding and hardfacing processes. The article substantiates the perspective of using exothermic additives introduced into core filler for flux-cored wire arc welding processes as a relatively cheap additional heat source, reducing energy consumption when melting filler materials, and increasing the deposition rate. The mixture design (MD) was selected as the design method to optimize the average values of current and voltage, as well as arc stability parameters depending on core filler composition. This article studies the influence of the introduction of exothermic addition (EA), as well as the ratios CuO/C and CuO/Al on arc stability for the FCAW S process. Parameters characterizing arc stability were determined using an oscillograph, and from the obtained oscillograms, an analysis was conducted on arc voltage and welding current signals during flux-cored arc welding. It was determined that various methods can be used to evaluate arc stability, which can be divided into two groups: graphical (current and voltage cyclograms, box plots with frequency histograms, ellipse parameters plotted on current, and voltage cyclograms) and statistical (standard variation and coefficients of variation for welding current and arc voltage). In this paper, a comprehensive evaluation of arc stability depending on the composition of the cored wire filler was carried out. It was determined that the most stable current parameters were observed for the flux-cored wire electrode with an average exothermic addition content at the level of EA = 26.5–28.58 wt.% and a high carbon content (low values of CuO/C = 3.75). Conversely, the lowest values of arc stability (CV(U) and Std(U)) were observed during hardfacing with a flux-cored wire electrode with a high CuO/Al ratio ≥ 4.5 and a content of exothermic addition in the core filler below the average EA < 29 wt.%. Mathematical models of mean values, standard deviation, coefficient of variation for welding current, and arc voltage were developed. The results indicated that the response surface prediction models had good accuracy and prediction ability. The developed mathematical models showed that the ratio of oxidizing agent to reducing agent in the composition of exothermic addition (CuO/Al) had the greatest influence on the welding current and arc voltage characteristics under investigation. The percentage of exothermic mixture in the core filler (EA) only affected the average welding current (Iaw) and the average arc voltage (Uaw). The graphite content expressed through the CuO/C ratio had a significant impact on welding current parameters as well as the coefficient of variation of arc voltage (CV(U)). Two welding parameters were selected for optimization: the mean welding current (Iaw) and the standard deviation of arc voltage (Std(U)). The best arc stability when using exothermic addition CuO-Al in the core filler was observed at CuO/Al = 3.6–3.9, CuO/C = 3.5–4.26, and at an average EA content of 29–38 wt.%. The significant influence of the CuO/Al and CuO/C ratios on arc voltage parameters can also be explained by their impact on the elemental composition of the welding arc (copper, cupric oxide (CuO), and Al2O3). The more complete this reaction, the higher the amount of easily vaporized copper (Cu) in the arc plasma, enhancing arc stability. The influence of core filler composition on the microstructure of deposited metal of the Fe-Cr-Cu-Ti alloy system was investigated. Full article
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14 pages, 8960 KiB  
Article
Experimental and Computational Study of Microhardness Evolution in the HAZ for Al–Cu–Li Alloys
by Stavroula Maritsa, Stavros Deligiannis, Petros E. Tsakiridis and Anna D. Zervaki
Crystals 2024, 14(3), 246; https://doi.org/10.3390/cryst14030246 - 1 Mar 2024
Viewed by 921
Abstract
The Laser Beam Welding (LBW) of aluminum alloys has attracted significant interest from industrial sectors, including the shipbuilding, automotive and aeronautics industries, as it expects to contribute to significant cost reduction associated with the production of high-quality welds. To comprehend the behavior of [...] Read more.
The Laser Beam Welding (LBW) of aluminum alloys has attracted significant interest from industrial sectors, including the shipbuilding, automotive and aeronautics industries, as it expects to contribute to significant cost reduction associated with the production of high-quality welds. To comprehend the behavior of welded structures in regard to their damage tolerance, the application of fracture mechanics serves as the instrumental tool. However, the methods employed overlook the changes in the microstructure within the Heat-Affected Zone (HAZ), which leads to the degradation of the mechanical properties of the material. The purpose of this study is to simulate microhardness evolution in the HAZ of AA2198-T351 LBW. The material represents the latest generation of Al-Cu-Li alloys, which exhibit improved mechanical properties, enhanced damage tolerance behavior, lower density and better corrosion and fatigue crack growth resistance than conventional Al-Cu alloys. In this work, the microhardness profile of LBW AA2198 was measured, and subsequently, through isothermal heat treatments on samples, the microhardness values of the HAZ were replicated. The conditions of the heat treatments (T, t) were selected in line with the thermal cycles that each area of the HAZ experienced during welding. ThermoCalc and DICTRA were employed in order to identify the strengthening precipitates and their evolution (dissolution and coarsening) during the weld thermal cycle. The microstructure of the heat-treated samples was studied employing LOM and TEM, and the strengthening precipitates and their characteristics (volume fraction and size) were defined and correlated to the calculations and the experimental conditions employed during welding. The main conclusion of this study is that it is feasible to imitate the microstructure evolution within the HAZ through the implementation of isothermal heat treatments. This implies that it is possible to fabricate samples for fatigue crack growth tests, enabling the experimental examination of the damage tolerance behavior in welded structures. Full article
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17 pages, 7665 KiB  
Article
Heat-Affected Zone Microstructural Study via Coupled Numerical/Physical Simulation in Welded Superduplex Stainless Steels
by Leonardo Oliveira Passos da Silva, Tiago Nunes Lima, Francisco Magalhães dos Santos Júnior, Bruna Callegari, Luís Fernando Folle and Rodrigo Santiago Coelho
Crystals 2024, 14(3), 204; https://doi.org/10.3390/cryst14030204 - 21 Feb 2024
Viewed by 863
Abstract
Superduplex stainless steels (SDSS) are known for their combination of good mechanical properties and excellent corrosion resistance, enabled by the microstructural balance between austenite and ferrite and an amount of alloying elements. Their application in welded components is, however, limited by the possibility [...] Read more.
Superduplex stainless steels (SDSS) are known for their combination of good mechanical properties and excellent corrosion resistance, enabled by the microstructural balance between austenite and ferrite and an amount of alloying elements. Their application in welded components is, however, limited by the possibility of the precipitation of intermetallic phases and microstructural misbalance, which might hinder their properties, especially in the heat-affected zone (HAZ). This work introduces a methodology that relies simultaneously on physical and numerical simulations to study the HAZ in a UNS S32750 SDSS. Dimensions of the fusion zone and thermal cycles were calibrated for a numerical model using preliminary welding trials. Numerically simulated cycles for each heat input (HI) were physically reproduced in a Gleeble® simulator, and the heat-treated samples were characterized and compared with real specimens welded using the same parameters. Thermal curves resulting from the numerical simulations were successfully replicated by the Gleeble®, indicating adequate application of the desired HI. The hardness and microstructural results from simulated and welded specimens were also found to be quite similar. Therefore, the proposed methodology showed itself adequate not only for the study of duplex stainless steels, but also of materials with similar thermal and mechanical properties, including the extrapolation of welding parameters. Full article
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21 pages, 27504 KiB  
Article
Particle Swarm Method for Optimization of ATIG Welding Process to Joint Mild Steel to 316L Stainless Steel
by Kamel Touileb, Rachid Djoudjou, Abousoufiane Ouis, Abdeljlil Chihaoui Hedhibi, Sahbi Boubaker and Mohamed M. Z. Ahmed
Crystals 2023, 13(9), 1377; https://doi.org/10.3390/cryst13091377 - 14 Sep 2023
Viewed by 860
Abstract
316L stainless steel joined to mild steel is widespread in several applications to reach a requested good association of mechanical properties at a lower cost. The activating tungsten inert gas (ATIG) weld was carried out using a modified flux composed of 76.63% SiO [...] Read more.
316L stainless steel joined to mild steel is widespread in several applications to reach a requested good association of mechanical properties at a lower cost. The activating tungsten inert gas (ATIG) weld was carried out using a modified flux composed of 76.63% SiO2 + 13.37% Cr2O3 + 10% NaF to meet standard recommendations in terms of limiting the root penetration. Modified optimal flux gave a depth of penetration 1.84 times greater than that of conventional tungsten inert gas (TIG) welds and a root penetration of up to 0.8 mm. The microstructure of the dissimilar joints was investigated using a scanning electron microscope and EDS analysis. The mechanical properties of the weld were not affected by the modified flux. The results show that the energy absorbed in the fusion zone in the case of ATIG weld (239 J/cm2) is greater than that of TIG weld (216 J/cm2). It was found that the weld bead obtained with the optimal flux combination in ATIG welding can better withstand sudden loads. The obtained UTS value (377 MPa) for ATIG welding was close to that of TIG welding (376 MPa). The average Vickers hardness readings for ATIG welds in the fusion zone are up to 277 HV, compared to 252 HV for conventional TIG welding. Full article
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20 pages, 8064 KiB  
Article
Effect of Microchemistry Elements in Relation of Laser Welding Parameters on the Morphology 304 Stainless Steel Welds Using Response Surface Methodology
by Kamel Touileb, Elawady Attia, Rachid Djoudjou, Abdejlil Chihaoui Hedhibi, Abdallah Benselama, Albaijan Ibrahim and Mohamed M. Z. Ahmed
Crystals 2023, 13(7), 1138; https://doi.org/10.3390/cryst13071138 - 21 Jul 2023
Cited by 1 | Viewed by 996
Abstract
Small differences in the contents of surface active elements can change flow direction and thus heat transfer, even for different batches of a given alloy. This study aims to determine the effects of sulfur on weld bead morphology in the laser process. The [...] Read more.
Small differences in the contents of surface active elements can change flow direction and thus heat transfer, even for different batches of a given alloy. This study aims to determine the effects of sulfur on weld bead morphology in the laser process. The paper presents the results related to the weld bead shape of two thin AISI 304 industrial stainless steel casts. One cast contains 80 ppm (0.008%) of sulfur, considered as a high sulfur content, and the other one contains 30 ppm (0.003%) sulfur, which can be considered low sulfur. The welds were executed using a CO2 laser. The effects of laser power (3.75, 3.67, 6 kW), welding speed (1.25, 2.40, 2.45, 3.6 m/min), focus point position (2, 7, 12 mm), and shield gas (Helium, mixed 40% helium + 60% argon and mixed 70% helium + 30% argon) with a flow rate of 10 L/min on the depth of the weld (D) and the aspect ratio (R = D/W) were investigated using RSM (response surface methodology). The experimental results show that the transfer of energy from the laser beam to the workpiece can be total in cases where the selected welding parameters prevent plasma formation. For the 304 HS cast, the focus point is the major factor in determining the depth of penetration, and its contribution is up to 52.35%. However, for 304 LS, the interaction between shield gas and focus point seems to play an important role, and the contribution of their interaction raises to 28% in relation to the laser depth of the weld. Moreover, the study shows that sulfur plays a surface-active role only in the case of partial penetration beads, so that a 56% partially penetrated weld supports the hypothesis of its surface-active role in the formation of the weld pool. However, a penetration of only 36% confirms the effects of a sulfur surface-active when the bead is fully penetrated. Full article
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14 pages, 7187 KiB  
Article
Structure–Property Correlation between Friction-Welded Work Hardenable Al-4.9Mg Alloy Joints
by Aditya M. Mahajan, K. Vamsi Krishna, M. J. Quamar, Ateekh Ur Rehman, Bharath Bandi and N. Kishore Babu
Crystals 2023, 13(7), 1119; https://doi.org/10.3390/cryst13071119 - 18 Jul 2023
Viewed by 981
Abstract
Friction welding of aluminum alloys holds immense potential for replacing riveted joints in the structural sections of the aeronautical and automotive sectors. This research aims to investigate the effects on the microstructural and mechanical properties when AA5083 H116 joints are subjected to rotary [...] Read more.
Friction welding of aluminum alloys holds immense potential for replacing riveted joints in the structural sections of the aeronautical and automotive sectors. This research aims to investigate the effects on the microstructural and mechanical properties when AA5083 H116 joints are subjected to rotary friction welding. To evaluate the quality of the welds, optical and scanning electron microanalysis techniques were utilized, revealing the formation of sound welds without porosity. The microstructural examination revealed distinct weld zones within the weldment, including the dynamically recrystallized zone (DRZ), thermo-mechanically affected zone (TMAZ), heat-affected zone (HAZ), and base metal (BM). During the friction-welding process, grain refinement occurred, leading to the development of fine equiaxed grains in the DRZ/weld zone. Tensile testing revealed that the weldment exhibited higher strength (YS: 301 ± 6 MPa; UTS: 425 ± 7 MPa) in the BM region compared to the base metal (YS: 207 ± 5 MPa; UTS: 385 ± 9 MPa). However, the weldment demonstrated slightly lower elongation (%El: 13 ± 2) compared to the base metal (%El: 15 ± 3). The decrease in ductility observed in the weldment can be attributed to the presence of distinct weld zones within the welded sample. Also, the tensile graph of the BM showed serrations throughout the curve, which is a characteristic phenomenon known as the Portevin–Le Chatelier effect (serrated yielding) in Al-Mg alloys. This effect occurs due to the influence of dynamic strain aging on the material’s macroscopic plastic deformation. Fractography analysis showcased a wide range of dimple sizes, indicating a ductile fracture mode in the weldment. These findings contribute to understanding the microstructural and mechanical behavior of AA5083 H116 joints subjected to rotary friction welding. Full article
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12 pages, 4796 KiB  
Article
Investigation of the Microstructure and Mechanical Properties in Friction Stir Welded Dissimilar Aluminium Alloy Joints via Sampling Direction
by Sipokazi Mabuwa and Velaphi Msomi
Crystals 2023, 13(7), 1108; https://doi.org/10.3390/cryst13071108 - 16 Jul 2023
Cited by 2 | Viewed by 1272
Abstract
This research study investigates the influence of sampling direction on the microstructure and mechanical properties of dissimilar joints formed by friction stir welding (FSW). The specimens were cut in two directions: perpendicular (transverse) and parallel (longitudinal) to the FSW joint. The tests conducted [...] Read more.
This research study investigates the influence of sampling direction on the microstructure and mechanical properties of dissimilar joints formed by friction stir welding (FSW). The specimens were cut in two directions: perpendicular (transverse) and parallel (longitudinal) to the FSW joint. The tests conducted included X-ray diffraction (XRD), macrostructure, microstructure, tensile, microhardness, and fractography analysis. Different phases were noted in the XRD patterns and explained, with the aluminum phase being the dominating one. The results further showed that the transverse dissimilar joint exhibited higher microhardness compared to the longitudinal dissimilar joint, which is consistent with the respective grain sizes. Moreover, the ultimate tensile strength of the longitudinal joint exceeded that of the transverse joints, showing a substantial 47% increase. Similarly, the elongation of the joints followed a similar trend, with the longitudinal joint displaying a significant 41% increase in elongation compared to the transverse joint. Fractographic analysis revealed ductile fracture behaviour in all joints. Full article
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