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DOI: 10.22184/1993-7296.FRos.2020.14.6.492.506
A quantitative and qualitative analysis of world trends in the field of laser welding of dissimilar metals for 2016–2019 is presented. It is highlighted that laser welding is most widespread for joints of steel with aluminum, titanium with aluminum, aluminum with copper. The analysis of the basic techniques and methods of welding dissimilar metals, the results of studying their influence on the metallurgy of the process, the microstructure and mechanical properties of joints. The emphasis is made on the description of the technique and methods of laser welding of aluminum with steel.
A quantitative and qualitative analysis of world trends in the field of laser welding of dissimilar metals for 2016–2019 is presented. It is highlighted that laser welding is most widespread for joints of steel with aluminum, titanium with aluminum, aluminum with copper. The analysis of the basic techniques and methods of welding dissimilar metals, the results of studying their influence on the metallurgy of the process, the microstructure and mechanical properties of joints. The emphasis is made on the description of the technique and methods of laser welding of aluminum with steel.
Теги: dissimilar metals intermetallic layer laser welding mechanical properties microstructure weldability интерметаллидный слой лазерная сварка механические свойства микроструктура разнородные металлы свариваемость
Laser Welding of Dissimilar Metals
S. V. Kuryntsev1, I. N. Shiganov2
Kazan National Research Technical University n. a. A. N. Tupolev – KAI, Kazan, Russia
Moscow State Technical University n. a. N. E. Bauman, Moscow, Russia
A quantitative and qualitative analysis of world trends in the field of laser welding of dissimilar metals for 2016–2019 is presented. It is highlighted that laser welding is most widespread for joints of steel with aluminum, titanium with aluminum, aluminum with copper. The analysis of the basic techniques and methods of welding dissimilar metals, the results of studying their influence on the metallurgy of the process, the microstructure and mechanical properties of joints. The emphasis is made on the description of the technique and methods of laser welding of aluminum with steel.
Key words: laser welding, dissimilar metals, weldability, microstructure, intermetallic layer, mechanical properties
Received on: 01.08.2020
Accepted on: 26.08.2020
INTRODUCTION
The main trend of modern structural engineering is to reduce the weight of the final product using materials and structures with high strength and low specific weight [1]. Examples of such materials are composite materials based on carbon fiber, high-strength duplex steels, porous or hollow materials [2, 3], obtained using additive technologies and taking into account topological optimization. In addition, such materials include multi-materials or hybrid structures consisting of several dissimilar materials connected to each other in some way, e. g., by welding, bolting or riveting, gluing, soldering, etc. [4].
As a rule, welded, brazed or glued joints provide the greatest strength and tightness of joints. The adhesion, weldability and solderability of dissimilar materials can be complicated by the difference in physical and thermomechanical properties of the materials to be joined and their surfaces [5, 6]. This requires the use of complex hybrid technologies based on thermal, mechanical, and chemical action on the workpieces being joined; such technologies include welding-brazing, welding-gluing, clinch-joints [7] etc. For example, the body of a modern passenger car by weight consists of approximately 96 kg of aluminum, 66 kg of steel, 11 kg of magnesium, 7 kg of plastic [4], so the issue of joining dissimilar materials is an urgent and promising science-intensive technological problem.
Understanding the physical, chemical and metallurgical processes occurring during welding and brazing of dissimilar materials is the basis for choosing the type and method of welding, techniques and welding technology in order to obtain a joint with the required characteristics. In fusion welding of dissimilar metals, it is necessary to consider both the physical properties of the materials being joined and the metallurgy of their interaction in the liquid state, which prevents the formation of a high-quality welded joint [5].
Due to the fact that fusion welding implies the inevitable melting of the material in the weld zone and heating to temperatures T = 0.8 Tm in the heat-affected zone, it is necessary to consider the processes of interaction of the materials to be joined during melting and crystallization. All processes of melting and crystallization, as well as the formation of intermetallic compounds, are reflected in the diagrams of the state of binary systems [8]. By the type of the state diagram of the two materials to be welded, it is possible to envisage the formation of a particular structure.
In this case, one should distinguish between the effect on the structure of the crystallization mechanism, on the one hand, and subsequent phase transformations in the solid state, on the other. The phase diagrams of the eutectic and peretectic types, the components of which upon melting form a homogeneous liquid with limited solubility, and in the solid state are practically insoluble in each other, are the most favorable. Melting and crystallization of such materials in the weld produces a homogeneous heterogeneous structure with alternating particles of constituent elements. Fusion welding of such materials is possible without much difficulty. If the components of the materials to be welded during melting and crystallization have limited or unlimited mutual solubility, then during welding of such materials, solid solutions with a concentration smoothly varying from the fusion line will be formed in the seam. The seam strength of such joints can be quite high. When welding materials with a limited solubility of the components in the weld, along with solid solutions, a eutectic or a permeate will be present, depending on the phase diagram.
However, there are materials that do not mix in a liquid state and form phase diagrams with no interaction at all. When such materials are melted in a seam, they delaminate, not providing the desired mechanical properties. Thus, when starting to develop a technology for welding dissimilar materials, it is necessary, first, to find out the type of their state diagram during melting and crystallization.
In practice, the main problem that reduces the mechanical and operational properties of welded joints from dissimilar alloys is the formation of an intermetallic layer (IML), which is very hard and brittle [9]. The intermetallic phase can be useful for an alloy; it can be a dispersed hardener that inhibits dislocations, if it is evenly distributed between grains in the bulk of the metal [5].
However, if the IML is present in the form of a continuous strip at the interface or on the fusion line of two metals, then in this case it will pose a threat to the destruction of the joint, the weak area will be the transition line or HAZ from the IML to the base metal.
Table 1 shows the characteristics of the possibility of welding some pairs of metals. As you can see from the table, only copper and nickel have excellent weldability. This is because these materials have a chemical affinity and form a solid substitution solution of unlimited solubility. The remaining metal pairs generally have satisfactory weldability. Therefore, an important task is to ensure uniformity of diffusion processes over the thickness of butt-welded materials.
One of the effective methods of welding dissimilar materials is laser welding [10–12]. When welding dissimilar metals, the main advantage is a high welding speed and concentration of energy, which allow minimizing the interaction time of the metals being joined, as a rule, having different melting points, limited mutual solubility, heat capacity and thermal conductivity coefficients. Minimization of the interaction time leads to the minimization of the formation of intermetallic compounds between the metals being welded, which usually have high hardness and brittleness, low thermal and electrical conductivity.
The purpose of the work is a quantitative and qualitative analysis of the world trends in laser welding of dissimilar metals, an overview of world trends, methods and techniques of joining.
ANALYSIS OF TRENDS IN WORLD PUBLICATIONS ON LASER WELDING OF DISSIMILAR MATERIALS
As the analysis of publications on the Scopus abstract database shows, over the past 4 years on the topic of laser welding of dissimilar metals, about 270 articles have been published, 70% of which are in high-rated journals, the rest in conference proceedings and translated journals. In fig. 1 shows the distribution of the number of articles on laser welding of various pairs of metals for 2016–2019 inclusive. As you can see, the largest number of publications is devoted to joining steel to aluminum (26%), these joints are widely used in the automotive industry, therefore, these works mainly describe the technologies of welding or welding-brazing of sheet blanks of small thicknesses (up to 2–3 mm). In second place among metal pairs is titanium + aluminum pair (9%); these joints are widely used in aircraft and rocketry, space products, in which the main requirement is weight minimization. It should also be noted here that titanium-magnesium joints (5%) are also used in the above-mentioned industries. In third place are joints of aluminum and copper (8%), this pair of metals is used in the electrical and thermal power industries. Publications about other metal pairs, such as nickel + titanium, titanium + steel, copper + steel, nickel + steel, titanium + magnesium, account for 3 to 6% of the total number of articles.
It should be noted that the number of articles on the topic of joining metallic materials with non-metallic (carbon fiber composites, organic glass, plastics) using laser radiation is about 9% of the total. As a rule, a laser beam is applied to a metal or non-metallic material in this lap joint type. When a metal is exposed to a laser beam, it is heated or melted to an incomplete depth, depending on the thickness, the non-metallic material on the opposite side is heated and interacts with the heated metal in a viscous fluid state. Thus, a not strong but tight connection is formed [13].
TECHNOLOGICAL FEATURES OF LASER WELDING OF DISSIMILAR METALS
The main technological methods used in laser welding of dissimilar metals are:
offset of the laser beam to one of the welded metals;
use of intermediate metals or coating.
When choosing the offset of the laser beam to one of the metals being welded, they are guided by various factors and properties of the metals being joined: the degree of absorption of laser radiation by the metal of a certain wavelength, the melting point, the wettability of one component to another, or vice versa, the mutual solubility of the components at the level of the crystal structure, the difference in heat capacity and thermal conductivity.
For example, when welding well-weldable copper to stainless steel, the laser beam is displaced onto the steel, the steel melts, wets and heats the copper through thermal conduction (heat transfer in a solid), forming metallic bonds. If the beam is directed to copper, then, firstly, laser radiation of almost all wavelengths in the IR spectrum will be reflected by 99% [11], and secondly, the thermal conductivity of copper is 5 times greater than that of iron [8, 14], heat generated by exposure to laser radiation will scatter rather than melt copper, etc.
In the case of welding limited weldable metals, e. g., steel with aluminum, basically the laser beam is shifted to aluminum, although its thermal conductivity and the degree of reflection of laser radiation are higher than that of steel, but the wettability of steel by molten liquid aluminum is higher than the wettability of aluminum by liquid iron [6]. Also, the melting point of iron is almost 3 times higher than the melting point of aluminum, that is, the melting of iron can lead to boiling of aluminum, and as a result, to the formation of defects. In this case, by shifting the laser beam in the range of 0.1–2 mm, depending on the speed and thickness of the workpieces being welded, the thickness of the IML formation can be controlled.
The use of intermediate metals or the application of coatings that are metallurgically compatible with both poorly welded metals are a widespread technique used in various types of welding, such as diffusion, explosion, pressure, etc. [5, 9]. If in the indicated types of welding this welding technique is used for the overlap type of joints, then in the case of laser welding it is used for both overlap joints and butt joints. When welding butt joints, the intermediate metal can be melted either directly by the laser beam or by thermal conduction when the laser beam is displaced onto one of the components to be welded. In the case of lap joints, the intermediate metal is heated conductively and does not always melt, since it is not directly affected by the laser beam. As a rule, most of the joints obtained by the above methods are welded-brazed. That is, for one metal, the process is characterized as welding: it melts, wetting another metal, for which the process is characterized as brazing. The mechanical properties of such compounds can reach 70–90% of the properties of a less strong metal [4].
In these technological methods, through a high degree of controllability of the parameters of laser radiation, it is possible to control overheating and the thickness of the transition layer or IML, which can significantly improve the quality of the connection and its mechanical and operational properties.
LASER WELDING
OF ALUMINUM ALLOYS WITH STEEL
As mentioned above, the most common pair of laser-welded metals are steel with aluminum, since they are most widely used as structural materials. The main physical properties of aluminum and iron are presented in Table 2. It can be seen from the presented data that the properties differ significantly, including at the level of atomic structure, in particular, the lattice constant differs by almost 1.5 times, the atomic radius of aluminum is 143 pm, iron 126 pm, the crystal lattice of aluminum is the same only with gamma iron.
Iron is a transition metal. In accordance with the phase diagram, it forms a eutectic with aluminum and has a low solubility in solid aluminum. Aluminum, in turn, dissolves well in alpha iron, forming the following stable phases Fe3Al, FeAl2, Fe2Al5, FeAl3, each of which has a certain region of homogeneity [5, 8, 15]. In view of the indicated differences in the structure and properties of aluminum and iron, fusion welding of these metals is a science-intensive technological task.
The work [16] presents the main types of welded-brazed joints used in the automotive industry (Fig. 3 a, b), in the technology used, the laser beam was directed to the filler wire, which in the molten state interacts with DX51D steel and AlMgSi1 alloy (Fig. 4), the materials being joined are not melted by the laser beam.
The authors presented the results of a study of laser welding-brazing using various filler materials (AlSi5, AlSi12, ZnAl2), the maximum strength values were obtained for specimens with a zinc-based filler material (220 MPa), specimens with an aluminum-based filler material (160–180 MPa). Fracture of the samples was observed along the HAZ of aluminum (Fig. 5 a, b).
The influence of the shape of the groove (Fig. 6 a, b, c) in butt welding of aluminum alloy 6061-T6 and steel DP590 is presented by the authors [17], and a comparative analysis of the results obtained with mathematical modeling of the distribution of the thermal field depending on the shape of the groove is carried out. The proposed models are verifiable. The tensile strength of the samples under study is in the range 108–145 MPa, the elongation is less than 1 mm, the highest values were for samples with the groove shown in Fig. 6c, they also had the minimum IML thickness (8.8 μm). The smallest value of ultimate tensile strength was observed for specimens with the groove shape shown in Fig. 6 a, they also had the greatest thickness of the IML.
In works [18–20], studies of overlapping welding of aluminum and steel sheets are described. In particular, in [18], studies are carried out on the influence of heat input and welding technology (exposure to a beam from the side of aluminum or from the side of steel) on the mechanical properties of welded joints. The authors conclude that the welding technique, in which the laser beam melts aluminum, is not preferable, since molten aluminum interacts too actively with steel, this leads to the formation of IML of large thickness, and in some cases to the formation of cracks.
Modeling the propagation of temperature fields during laser welding with a defocused beam with a diameter of 13 mm overlapping steel and aluminum, when exposed to a beam on steel, is described by the authors [19]. The proposed model and the established boundary conditions show the adequacy of the thermal cycle model and a real experiment, in particular, the depth and width of the penetration, on which the mechanical properties depend. The authors establish that the joint has the maximum mechanical properties during shear tests under the condition of the minimum IML and the maximum width of the interaction region between steel and aluminum, provided by a defocused laser beam.
In [20], studies of welding of steel and aluminum with a bifurcated laser beam with an overlap, when exposed to the steel, are described, while the beam was bifurcated along or across the welding direction, the distance between the beams and the ratio of the power of the beams vary. The maximum mechanical properties in shear tests (109.2 N / mm) were obtained with a ratio of the power of the beams 3 / 2 and their transverse arrangement relative to the welding direction.
The results of research and mechanical tests of a bus body element, obtained by laser welding of steel with aluminum, are given in [21]. In this work, it is shown that the obtained joints have the necessary strength characteristics (125–130 MPa), sufficient to ensure the safe operation of passenger vehicles.
Hybrid laser-arc butt welding of steel and aluminum is described in [22, 23], in particular, the effect of laser beam offset, the distance between the beam and the arc, and the effect of welding parameters are investigated. The authors of [22] compared two techniques – the shift of the laser beam onto steel and hybrid laser-arc welding (the arc and the beam are directed into the joint). As a result of the research, it was found that the more preferable technique is to shift the beam to steel, since in this case the process is accompanied by higher cooling rates compared to laser-arc welding and helps to minimize the thickness of the formed IML (6 μm).
The authors of [23] describe the technology of laser-arc welding-brazing with an intermediate material pressed from a powder based on aluminum (Al80Zn8Mg7Mn2Si2), while the beam and arc are directed to the intermediate material, a comparison is made with laser welding without the use of an electric arc. The authors conclude that the use of two heat sources is an effective technology for increasing the spreading of the intermediate material and the formation of a welded-brazed joint with a tensile strength of 163 MPa and an IML thickness of 8.7 μm.
The paper [24] investigates the technology of laser welding, and the features of subsequent machining of rods made of steel and aluminum. An interesting and promising technology for producing T‑joints was proposed by the authors [25]. The essence of the technology lies in the fact that a sheet of aluminum is inserted into a groove previously prepared on a steel sheet with a permissible variation of 0.2 mm on each side, then on the reverse side of the steel sheet, a defocused laser beam is heated along the trajectory of the groove (Fig. 7 a). The power of the laser beam is selected in such a way that the steel sheet is heated, through which, through thermal conduction, heating and melting of aluminum would occur, similar to the technology presented in [19], which in turn, by wetting the steel with molten aluminum, would lead to the formation of metal bonds between the end face of the aluminum sheet and the metal of the groove cavity of the steel sheet. Also, as a result of uneven thermal effect on the steel sheet in the area of smaller thickness, mechanical compression of the aluminum sheet by the metal of the groove cavity occurs (Fig. 7 a, b), which increases the mechanical characteristics of the joint. The thickness of the IML in the joint obtained using the proposed technique is about 5 microns.
The effect of the displacement of a laser beam performing circular oscillatory movements along a diameter of 0.5 mm on aluminum in hybrid laser-arc butt welding with steel sheets 1.8 mm thick is described by the authors [26]. The main technological parameter is the distance of displacement of the initial point of the laser beam impact, which is within the range of 0–1 mm (step of 0.2 mm) from the line of joint between aluminum and steel (Fig. 8).
The resulting joint is welded-brazed, since aluminum was melted, however, in contrast to welding without circular oscillations with a laser beam, the researchers discovered some features of the welded-brazed joint obtained by the presented technology. When melting aluminum-based alloys with a laser beam, a cone-shaped weld pool is formed without oscillation, while when melting with a circularly oscillating laser beam, a cylindrical weld pool will be formed. This, in turn, leads to a more uniform in depth interaction of molten aluminum with steel in the lower and upper parts of the joint and, as a result, to the formation of an IML that is more uniform in thickness (~ 1.3 μm). By shifting the laser beam by 0.8 mm, joints were obtained having a tensile strength of about 160 MPa. The authors also presented a model of the interaction of aluminum and iron atoms and a model of the formation of IML depending on the displacement distance.
The rest of the works describe the influence of methods, basic technological parameters, techniques and approaches, such as the choice of filler material, shielding gas, the use of various coatings of the metals to be joined, the use of two-beam laser welding, several works on remote high-speed welding have been published.
CONCLUSION
The research results lead to the following conclusions:
Laser welding is a promising type for joining dissimilar metals. The main advantages of laser welding in this area are the precision of the action, the ability to accurately control the melting process of the materials to be joined, and the short residence time of the materials being welded in the molten state, which helps to minimize the formation of an intermetallic layer, which is the main problem in welding poorly welded metals. In addition, lower specific heat input helps to minimize thermal deformations.
With overlap welding or welding of similar joints of steel and aluminum, it is rational to direct the laser beam to the steel, through thermal conduction, the steel heats the aluminum, which leads to controlled melting of its surface and the formation of a minimal IML in the welded-soldered joint.
The butt joint of these pairs of metals, as a rule, is characterized as a welded-brazed joint, that is, for aluminum it is welding, and for steel it is brazing. In this case, the most preferable is the technique of shifting the laser beam to aluminum, which has a lower melting point and good wettability of steel in a liquid state. The ultimate strength of such joints reaches 150–160 MPa, which is 70–80% of the strength of the welded aluminum alloys and is acceptable for some structures.
The next part of the paper will present materials and research results on welding of such metal pairs as titanium + steel, steel + nickel, titanium + aluminum, nickel + titanium, etc.
REFERENCES
Antipov V. V., Serebrennikova N. YU. Konovalov A. N., Nefedova YU. N. Perspektivy primeneniya v aviacionnyh konstrukciyah sloistyh metallopolimernyh materialov na osnove alyuminievyh splavov. Aviacionnye materialy i tekhnologii. 2020; 58: 45–53.
Bashin K. A., Torsunov R. A. Semenov S. V. Metody topologicheskoj optimizacii konstrukcij, primenyayushchihsya v aerokosmicheskoj otrasli. Vestnik Permskogo nacional’nogo issledovatel’skogo politekhnicheskogo universiteta. Aerokosmicheskaya tekhnika. 2017; 51: 51–61.
Sklyar, M. O., Turichin, G.A., Klimova, O.G., Zotov, O.G., Topalov, I. K. Issledovanie vliyaniya parametrov pryamogo lazernogo vyrashchivaniya na mikrostrukturu izdelij iz stali 316L. Stal’. 2016; 12: 71–75.
Martinsen K., Hu S. J., Carlson B. E. Joining of dissimilar materials. CIRP Annals – Manufacturing Technology. 2015; 64: 679–699. DOI: 10.1016 / j.cirp.2015.05.006.
Ryablov V. R., Rabkin D. M., Kurochko R. S., Strizhevskaya L. G. Svarka raznorodnyh metallov i splavov. – M.: Mashinostroenie. 1984. 239 pp.
Lashko S. V., Lashko N. F. Pajka metallov. 4-e izd., pererab. i dop. – M.: Izd. Mashinostroenie, 1988. 376 pp.
Zakirov I. M., Sosov A. V., Nikitin A. V., Lukankin S. A. Ispytanie klinch-soedineniya na prochnost’. Vestnik Kazanskogo gosudarstvennogo tekhnicheskogo universiteta im. A. N. Tupoleva. 2012; 4(2): 58–60.
Arzamasov B. N., Makarova V. I., Muhin G. G. Materialovedenie: uchebnik dlya vuzov / 3-e izd., stereotip. – M: Izd-vo MGTU im. N. E. Baumana. 2002. 648 pp.
Lyushinskij A. V. Diffuzionnaya svarka raznorodnyh materialov. – M: Mashinostroenie. 2006. 208 pp. Ser. Vysshee professional’noe obrazovanie.
Grigoryanc A. G., SHiganov I.N., Misyurov A. I. Tekhnologicheskie processy lazernoj obrabotki. – M.: Izd-vo MGTU im. N.E Baumana. 2006. 664 pp.
SHiganov I. N., Kuryncev S. V. Sovremennye tendencii lazernoj svarki. Part I. Naukoemkie tekhnologii v mashinostroenii. 2015; 6: 35–42.
SHiganov I. N., Kuryncev S. V. Sovremennye tendencii lazernoj svarki. Part II. Naukoemkie tekhnologii v mashinostroenii. 2015; 9: 15–20.
Patent RU2678002 C1. Sposob soedineniya metallicheskogo materiala s kompozicionnym materialom lazernym luchom / Kuryncev S. V.
Kuryncev S. V., SHiganov I. N. Svarka austenitnoj stali s med’yu rasfokusirovannym izlucheniem volokonnogo lazera. Svarochnoe proizvodstvo. 2017; 4: 7–11.
Lukin M. A. Kontaktnaya stykovaya svarka oplavleniem paketa alyuminievyh listov so stal’nym sterzhnem. Svarochnoe proizvodstvo. 2020; 3: 38–43.
Frank S. Flux-free laser joining of aluminum and galvanized steel. Journal of Materials Processing Technology. 2015, 222: 365–372. DOI: 10.1016 / j.jmatprotec.2015.03.032.
Li LQ, Xia HB, Tan CW, Ma NS. Effect of groove shape on laser welding-brazing Al to steel. Journal of Materials Processing Technology. 2018; 252:573–81. DOI: 10.1016 / j.jmatprotec.2017.10.025.
Seffer O, Pfeifer R, Springer A, Kaierle S. Investigations on laser beam welding of different dissimilar joints of steel and aluminum alloys for automotive lightweight construction. Laser Assisted Net Shape Engineering 9 International Conference on Photonic Technologies Proceedings of the Lane 2016. 2016; 83:383–95. DOI: 10.1016 / j.phpro.2016.08.040.
Meco S, Cozzolino L, Ganguly S, Williams S, McPherson N. Laser welding of steel to aluminium: Thermal modelling and joint strength analysis. Journal of Materials Processing Technology. 2017;247:121–33. DOI: 10.1016 / j.jmatprotec.2017.04.002.
Cui L, Chen HX, Chen BX, He DY. Welding of Dissimilar Steel / Al Joints Using Dual-Beam Lasers with Side-by-Side Configuration. Metals. 2018; 8(12):21. DOI: 10.3390 / met8121017.
Lyuhter A. B., SHlegel’ A. N., Leont’ev A. A., Gusev D. S. Rezul’taty mekhanicheskih ispytanij korpusnyh elementov avtobusov, poluchennyh lazernoj svarkoj stal’nogo profilya St3 s alyuminievoj oblicovkoj AMg2M. Cvetnye metally. 2017; 10: 85–89.
Casalino G, Leo P, Mortello M, Perulli P, Varone A. Effects of Laser Offset and Hybrid Welding on Microstructure and IMC in Fe-Al Dissimilar Welding. Metals. 2017; 7(8). DOI: 10.3390 / met7080282.
Huang JK, He J, Yu XQ, Li CL, Fan D. The study of mechanical strength for fusion-brazed butt joint between aluminum alloy and galvanized steel by arc-assisted laser welding. Journal of Manufacturing Processes. 2017; 25:126–33. DOI: 10.1016 / j.jmapro.2016.11.014.
Nothdurft S, Prasanthan V, Denkena B, Breidenstein B, Grove T, Ohrdes H, et al. Surface Integrity of Laser Beam Welded Steel-Aluminium Alloy Hybrid Shafts after Turning. Metals. 2019; 9(2). DOI: 10.3390 / met9020134
Meco S, Ganguly S, Williams S, McPherson N. Design of laser welding applied to T joints between steel and aluminium. Journal of Materials Processing Technology. 2019; 268:132–9. DOI: 10.1016 / j.jmatprotec.2019.01.003.
Meng YF, Gong MC, Zhang S, Zhang YZ, Gao M. Effects of oscillating laser offset on microstructure and properties of dissimilar Al / steel butt-joint. Optics and Lasers in Engineering. 2020;128. DOI: 10.1016 / j.optlaseng.2020.106037.
ABOUT AUTHORS
Kuryntsev Sergey V., Candidate of Sciences (Economics), e-mail kuryntsev16@mail.ru, Kazan National Research Technical University named after A. N. Tupolev – KAI, Kazan, Russia.
Igor Nikolaevich Shiganov, Doctor of Technical Sciences, Professor, Moscow State Technical University named after N. E. Moscow, Russia.
Contributions of authors
Kuryntsev S. V. – idea, translation and analysis of material, work with graphic part, results processing. Shiganov I. N. – discussion, suggestions and comments, material analysis.
Conflict of interest
The authors declare no real or potential conflicts of interest.
S. V. Kuryntsev1, I. N. Shiganov2
Kazan National Research Technical University n. a. A. N. Tupolev – KAI, Kazan, Russia
Moscow State Technical University n. a. N. E. Bauman, Moscow, Russia
A quantitative and qualitative analysis of world trends in the field of laser welding of dissimilar metals for 2016–2019 is presented. It is highlighted that laser welding is most widespread for joints of steel with aluminum, titanium with aluminum, aluminum with copper. The analysis of the basic techniques and methods of welding dissimilar metals, the results of studying their influence on the metallurgy of the process, the microstructure and mechanical properties of joints. The emphasis is made on the description of the technique and methods of laser welding of aluminum with steel.
Key words: laser welding, dissimilar metals, weldability, microstructure, intermetallic layer, mechanical properties
Received on: 01.08.2020
Accepted on: 26.08.2020
INTRODUCTION
The main trend of modern structural engineering is to reduce the weight of the final product using materials and structures with high strength and low specific weight [1]. Examples of such materials are composite materials based on carbon fiber, high-strength duplex steels, porous or hollow materials [2, 3], obtained using additive technologies and taking into account topological optimization. In addition, such materials include multi-materials or hybrid structures consisting of several dissimilar materials connected to each other in some way, e. g., by welding, bolting or riveting, gluing, soldering, etc. [4].
As a rule, welded, brazed or glued joints provide the greatest strength and tightness of joints. The adhesion, weldability and solderability of dissimilar materials can be complicated by the difference in physical and thermomechanical properties of the materials to be joined and their surfaces [5, 6]. This requires the use of complex hybrid technologies based on thermal, mechanical, and chemical action on the workpieces being joined; such technologies include welding-brazing, welding-gluing, clinch-joints [7] etc. For example, the body of a modern passenger car by weight consists of approximately 96 kg of aluminum, 66 kg of steel, 11 kg of magnesium, 7 kg of plastic [4], so the issue of joining dissimilar materials is an urgent and promising science-intensive technological problem.
Understanding the physical, chemical and metallurgical processes occurring during welding and brazing of dissimilar materials is the basis for choosing the type and method of welding, techniques and welding technology in order to obtain a joint with the required characteristics. In fusion welding of dissimilar metals, it is necessary to consider both the physical properties of the materials being joined and the metallurgy of their interaction in the liquid state, which prevents the formation of a high-quality welded joint [5].
Due to the fact that fusion welding implies the inevitable melting of the material in the weld zone and heating to temperatures T = 0.8 Tm in the heat-affected zone, it is necessary to consider the processes of interaction of the materials to be joined during melting and crystallization. All processes of melting and crystallization, as well as the formation of intermetallic compounds, are reflected in the diagrams of the state of binary systems [8]. By the type of the state diagram of the two materials to be welded, it is possible to envisage the formation of a particular structure.
In this case, one should distinguish between the effect on the structure of the crystallization mechanism, on the one hand, and subsequent phase transformations in the solid state, on the other. The phase diagrams of the eutectic and peretectic types, the components of which upon melting form a homogeneous liquid with limited solubility, and in the solid state are practically insoluble in each other, are the most favorable. Melting and crystallization of such materials in the weld produces a homogeneous heterogeneous structure with alternating particles of constituent elements. Fusion welding of such materials is possible without much difficulty. If the components of the materials to be welded during melting and crystallization have limited or unlimited mutual solubility, then during welding of such materials, solid solutions with a concentration smoothly varying from the fusion line will be formed in the seam. The seam strength of such joints can be quite high. When welding materials with a limited solubility of the components in the weld, along with solid solutions, a eutectic or a permeate will be present, depending on the phase diagram.
However, there are materials that do not mix in a liquid state and form phase diagrams with no interaction at all. When such materials are melted in a seam, they delaminate, not providing the desired mechanical properties. Thus, when starting to develop a technology for welding dissimilar materials, it is necessary, first, to find out the type of their state diagram during melting and crystallization.
In practice, the main problem that reduces the mechanical and operational properties of welded joints from dissimilar alloys is the formation of an intermetallic layer (IML), which is very hard and brittle [9]. The intermetallic phase can be useful for an alloy; it can be a dispersed hardener that inhibits dislocations, if it is evenly distributed between grains in the bulk of the metal [5].
However, if the IML is present in the form of a continuous strip at the interface or on the fusion line of two metals, then in this case it will pose a threat to the destruction of the joint, the weak area will be the transition line or HAZ from the IML to the base metal.
Table 1 shows the characteristics of the possibility of welding some pairs of metals. As you can see from the table, only copper and nickel have excellent weldability. This is because these materials have a chemical affinity and form a solid substitution solution of unlimited solubility. The remaining metal pairs generally have satisfactory weldability. Therefore, an important task is to ensure uniformity of diffusion processes over the thickness of butt-welded materials.
One of the effective methods of welding dissimilar materials is laser welding [10–12]. When welding dissimilar metals, the main advantage is a high welding speed and concentration of energy, which allow minimizing the interaction time of the metals being joined, as a rule, having different melting points, limited mutual solubility, heat capacity and thermal conductivity coefficients. Minimization of the interaction time leads to the minimization of the formation of intermetallic compounds between the metals being welded, which usually have high hardness and brittleness, low thermal and electrical conductivity.
The purpose of the work is a quantitative and qualitative analysis of the world trends in laser welding of dissimilar metals, an overview of world trends, methods and techniques of joining.
ANALYSIS OF TRENDS IN WORLD PUBLICATIONS ON LASER WELDING OF DISSIMILAR MATERIALS
As the analysis of publications on the Scopus abstract database shows, over the past 4 years on the topic of laser welding of dissimilar metals, about 270 articles have been published, 70% of which are in high-rated journals, the rest in conference proceedings and translated journals. In fig. 1 shows the distribution of the number of articles on laser welding of various pairs of metals for 2016–2019 inclusive. As you can see, the largest number of publications is devoted to joining steel to aluminum (26%), these joints are widely used in the automotive industry, therefore, these works mainly describe the technologies of welding or welding-brazing of sheet blanks of small thicknesses (up to 2–3 mm). In second place among metal pairs is titanium + aluminum pair (9%); these joints are widely used in aircraft and rocketry, space products, in which the main requirement is weight minimization. It should also be noted here that titanium-magnesium joints (5%) are also used in the above-mentioned industries. In third place are joints of aluminum and copper (8%), this pair of metals is used in the electrical and thermal power industries. Publications about other metal pairs, such as nickel + titanium, titanium + steel, copper + steel, nickel + steel, titanium + magnesium, account for 3 to 6% of the total number of articles.
It should be noted that the number of articles on the topic of joining metallic materials with non-metallic (carbon fiber composites, organic glass, plastics) using laser radiation is about 9% of the total. As a rule, a laser beam is applied to a metal or non-metallic material in this lap joint type. When a metal is exposed to a laser beam, it is heated or melted to an incomplete depth, depending on the thickness, the non-metallic material on the opposite side is heated and interacts with the heated metal in a viscous fluid state. Thus, a not strong but tight connection is formed [13].
TECHNOLOGICAL FEATURES OF LASER WELDING OF DISSIMILAR METALS
The main technological methods used in laser welding of dissimilar metals are:
offset of the laser beam to one of the welded metals;
use of intermediate metals or coating.
When choosing the offset of the laser beam to one of the metals being welded, they are guided by various factors and properties of the metals being joined: the degree of absorption of laser radiation by the metal of a certain wavelength, the melting point, the wettability of one component to another, or vice versa, the mutual solubility of the components at the level of the crystal structure, the difference in heat capacity and thermal conductivity.
For example, when welding well-weldable copper to stainless steel, the laser beam is displaced onto the steel, the steel melts, wets and heats the copper through thermal conduction (heat transfer in a solid), forming metallic bonds. If the beam is directed to copper, then, firstly, laser radiation of almost all wavelengths in the IR spectrum will be reflected by 99% [11], and secondly, the thermal conductivity of copper is 5 times greater than that of iron [8, 14], heat generated by exposure to laser radiation will scatter rather than melt copper, etc.
In the case of welding limited weldable metals, e. g., steel with aluminum, basically the laser beam is shifted to aluminum, although its thermal conductivity and the degree of reflection of laser radiation are higher than that of steel, but the wettability of steel by molten liquid aluminum is higher than the wettability of aluminum by liquid iron [6]. Also, the melting point of iron is almost 3 times higher than the melting point of aluminum, that is, the melting of iron can lead to boiling of aluminum, and as a result, to the formation of defects. In this case, by shifting the laser beam in the range of 0.1–2 mm, depending on the speed and thickness of the workpieces being welded, the thickness of the IML formation can be controlled.
The use of intermediate metals or the application of coatings that are metallurgically compatible with both poorly welded metals are a widespread technique used in various types of welding, such as diffusion, explosion, pressure, etc. [5, 9]. If in the indicated types of welding this welding technique is used for the overlap type of joints, then in the case of laser welding it is used for both overlap joints and butt joints. When welding butt joints, the intermediate metal can be melted either directly by the laser beam or by thermal conduction when the laser beam is displaced onto one of the components to be welded. In the case of lap joints, the intermediate metal is heated conductively and does not always melt, since it is not directly affected by the laser beam. As a rule, most of the joints obtained by the above methods are welded-brazed. That is, for one metal, the process is characterized as welding: it melts, wetting another metal, for which the process is characterized as brazing. The mechanical properties of such compounds can reach 70–90% of the properties of a less strong metal [4].
In these technological methods, through a high degree of controllability of the parameters of laser radiation, it is possible to control overheating and the thickness of the transition layer or IML, which can significantly improve the quality of the connection and its mechanical and operational properties.
LASER WELDING
OF ALUMINUM ALLOYS WITH STEEL
As mentioned above, the most common pair of laser-welded metals are steel with aluminum, since they are most widely used as structural materials. The main physical properties of aluminum and iron are presented in Table 2. It can be seen from the presented data that the properties differ significantly, including at the level of atomic structure, in particular, the lattice constant differs by almost 1.5 times, the atomic radius of aluminum is 143 pm, iron 126 pm, the crystal lattice of aluminum is the same only with gamma iron.
Iron is a transition metal. In accordance with the phase diagram, it forms a eutectic with aluminum and has a low solubility in solid aluminum. Aluminum, in turn, dissolves well in alpha iron, forming the following stable phases Fe3Al, FeAl2, Fe2Al5, FeAl3, each of which has a certain region of homogeneity [5, 8, 15]. In view of the indicated differences in the structure and properties of aluminum and iron, fusion welding of these metals is a science-intensive technological task.
The work [16] presents the main types of welded-brazed joints used in the automotive industry (Fig. 3 a, b), in the technology used, the laser beam was directed to the filler wire, which in the molten state interacts with DX51D steel and AlMgSi1 alloy (Fig. 4), the materials being joined are not melted by the laser beam.
The authors presented the results of a study of laser welding-brazing using various filler materials (AlSi5, AlSi12, ZnAl2), the maximum strength values were obtained for specimens with a zinc-based filler material (220 MPa), specimens with an aluminum-based filler material (160–180 MPa). Fracture of the samples was observed along the HAZ of aluminum (Fig. 5 a, b).
The influence of the shape of the groove (Fig. 6 a, b, c) in butt welding of aluminum alloy 6061-T6 and steel DP590 is presented by the authors [17], and a comparative analysis of the results obtained with mathematical modeling of the distribution of the thermal field depending on the shape of the groove is carried out. The proposed models are verifiable. The tensile strength of the samples under study is in the range 108–145 MPa, the elongation is less than 1 mm, the highest values were for samples with the groove shown in Fig. 6c, they also had the minimum IML thickness (8.8 μm). The smallest value of ultimate tensile strength was observed for specimens with the groove shape shown in Fig. 6 a, they also had the greatest thickness of the IML.
In works [18–20], studies of overlapping welding of aluminum and steel sheets are described. In particular, in [18], studies are carried out on the influence of heat input and welding technology (exposure to a beam from the side of aluminum or from the side of steel) on the mechanical properties of welded joints. The authors conclude that the welding technique, in which the laser beam melts aluminum, is not preferable, since molten aluminum interacts too actively with steel, this leads to the formation of IML of large thickness, and in some cases to the formation of cracks.
Modeling the propagation of temperature fields during laser welding with a defocused beam with a diameter of 13 mm overlapping steel and aluminum, when exposed to a beam on steel, is described by the authors [19]. The proposed model and the established boundary conditions show the adequacy of the thermal cycle model and a real experiment, in particular, the depth and width of the penetration, on which the mechanical properties depend. The authors establish that the joint has the maximum mechanical properties during shear tests under the condition of the minimum IML and the maximum width of the interaction region between steel and aluminum, provided by a defocused laser beam.
In [20], studies of welding of steel and aluminum with a bifurcated laser beam with an overlap, when exposed to the steel, are described, while the beam was bifurcated along or across the welding direction, the distance between the beams and the ratio of the power of the beams vary. The maximum mechanical properties in shear tests (109.2 N / mm) were obtained with a ratio of the power of the beams 3 / 2 and their transverse arrangement relative to the welding direction.
The results of research and mechanical tests of a bus body element, obtained by laser welding of steel with aluminum, are given in [21]. In this work, it is shown that the obtained joints have the necessary strength characteristics (125–130 MPa), sufficient to ensure the safe operation of passenger vehicles.
Hybrid laser-arc butt welding of steel and aluminum is described in [22, 23], in particular, the effect of laser beam offset, the distance between the beam and the arc, and the effect of welding parameters are investigated. The authors of [22] compared two techniques – the shift of the laser beam onto steel and hybrid laser-arc welding (the arc and the beam are directed into the joint). As a result of the research, it was found that the more preferable technique is to shift the beam to steel, since in this case the process is accompanied by higher cooling rates compared to laser-arc welding and helps to minimize the thickness of the formed IML (6 μm).
The authors of [23] describe the technology of laser-arc welding-brazing with an intermediate material pressed from a powder based on aluminum (Al80Zn8Mg7Mn2Si2), while the beam and arc are directed to the intermediate material, a comparison is made with laser welding without the use of an electric arc. The authors conclude that the use of two heat sources is an effective technology for increasing the spreading of the intermediate material and the formation of a welded-brazed joint with a tensile strength of 163 MPa and an IML thickness of 8.7 μm.
The paper [24] investigates the technology of laser welding, and the features of subsequent machining of rods made of steel and aluminum. An interesting and promising technology for producing T‑joints was proposed by the authors [25]. The essence of the technology lies in the fact that a sheet of aluminum is inserted into a groove previously prepared on a steel sheet with a permissible variation of 0.2 mm on each side, then on the reverse side of the steel sheet, a defocused laser beam is heated along the trajectory of the groove (Fig. 7 a). The power of the laser beam is selected in such a way that the steel sheet is heated, through which, through thermal conduction, heating and melting of aluminum would occur, similar to the technology presented in [19], which in turn, by wetting the steel with molten aluminum, would lead to the formation of metal bonds between the end face of the aluminum sheet and the metal of the groove cavity of the steel sheet. Also, as a result of uneven thermal effect on the steel sheet in the area of smaller thickness, mechanical compression of the aluminum sheet by the metal of the groove cavity occurs (Fig. 7 a, b), which increases the mechanical characteristics of the joint. The thickness of the IML in the joint obtained using the proposed technique is about 5 microns.
The effect of the displacement of a laser beam performing circular oscillatory movements along a diameter of 0.5 mm on aluminum in hybrid laser-arc butt welding with steel sheets 1.8 mm thick is described by the authors [26]. The main technological parameter is the distance of displacement of the initial point of the laser beam impact, which is within the range of 0–1 mm (step of 0.2 mm) from the line of joint between aluminum and steel (Fig. 8).
The resulting joint is welded-brazed, since aluminum was melted, however, in contrast to welding without circular oscillations with a laser beam, the researchers discovered some features of the welded-brazed joint obtained by the presented technology. When melting aluminum-based alloys with a laser beam, a cone-shaped weld pool is formed without oscillation, while when melting with a circularly oscillating laser beam, a cylindrical weld pool will be formed. This, in turn, leads to a more uniform in depth interaction of molten aluminum with steel in the lower and upper parts of the joint and, as a result, to the formation of an IML that is more uniform in thickness (~ 1.3 μm). By shifting the laser beam by 0.8 mm, joints were obtained having a tensile strength of about 160 MPa. The authors also presented a model of the interaction of aluminum and iron atoms and a model of the formation of IML depending on the displacement distance.
The rest of the works describe the influence of methods, basic technological parameters, techniques and approaches, such as the choice of filler material, shielding gas, the use of various coatings of the metals to be joined, the use of two-beam laser welding, several works on remote high-speed welding have been published.
CONCLUSION
The research results lead to the following conclusions:
Laser welding is a promising type for joining dissimilar metals. The main advantages of laser welding in this area are the precision of the action, the ability to accurately control the melting process of the materials to be joined, and the short residence time of the materials being welded in the molten state, which helps to minimize the formation of an intermetallic layer, which is the main problem in welding poorly welded metals. In addition, lower specific heat input helps to minimize thermal deformations.
With overlap welding or welding of similar joints of steel and aluminum, it is rational to direct the laser beam to the steel, through thermal conduction, the steel heats the aluminum, which leads to controlled melting of its surface and the formation of a minimal IML in the welded-soldered joint.
The butt joint of these pairs of metals, as a rule, is characterized as a welded-brazed joint, that is, for aluminum it is welding, and for steel it is brazing. In this case, the most preferable is the technique of shifting the laser beam to aluminum, which has a lower melting point and good wettability of steel in a liquid state. The ultimate strength of such joints reaches 150–160 MPa, which is 70–80% of the strength of the welded aluminum alloys and is acceptable for some structures.
The next part of the paper will present materials and research results on welding of such metal pairs as titanium + steel, steel + nickel, titanium + aluminum, nickel + titanium, etc.
REFERENCES
Antipov V. V., Serebrennikova N. YU. Konovalov A. N., Nefedova YU. N. Perspektivy primeneniya v aviacionnyh konstrukciyah sloistyh metallopolimernyh materialov na osnove alyuminievyh splavov. Aviacionnye materialy i tekhnologii. 2020; 58: 45–53.
Bashin K. A., Torsunov R. A. Semenov S. V. Metody topologicheskoj optimizacii konstrukcij, primenyayushchihsya v aerokosmicheskoj otrasli. Vestnik Permskogo nacional’nogo issledovatel’skogo politekhnicheskogo universiteta. Aerokosmicheskaya tekhnika. 2017; 51: 51–61.
Sklyar, M. O., Turichin, G.A., Klimova, O.G., Zotov, O.G., Topalov, I. K. Issledovanie vliyaniya parametrov pryamogo lazernogo vyrashchivaniya na mikrostrukturu izdelij iz stali 316L. Stal’. 2016; 12: 71–75.
Martinsen K., Hu S. J., Carlson B. E. Joining of dissimilar materials. CIRP Annals – Manufacturing Technology. 2015; 64: 679–699. DOI: 10.1016 / j.cirp.2015.05.006.
Ryablov V. R., Rabkin D. M., Kurochko R. S., Strizhevskaya L. G. Svarka raznorodnyh metallov i splavov. – M.: Mashinostroenie. 1984. 239 pp.
Lashko S. V., Lashko N. F. Pajka metallov. 4-e izd., pererab. i dop. – M.: Izd. Mashinostroenie, 1988. 376 pp.
Zakirov I. M., Sosov A. V., Nikitin A. V., Lukankin S. A. Ispytanie klinch-soedineniya na prochnost’. Vestnik Kazanskogo gosudarstvennogo tekhnicheskogo universiteta im. A. N. Tupoleva. 2012; 4(2): 58–60.
Arzamasov B. N., Makarova V. I., Muhin G. G. Materialovedenie: uchebnik dlya vuzov / 3-e izd., stereotip. – M: Izd-vo MGTU im. N. E. Baumana. 2002. 648 pp.
Lyushinskij A. V. Diffuzionnaya svarka raznorodnyh materialov. – M: Mashinostroenie. 2006. 208 pp. Ser. Vysshee professional’noe obrazovanie.
Grigoryanc A. G., SHiganov I.N., Misyurov A. I. Tekhnologicheskie processy lazernoj obrabotki. – M.: Izd-vo MGTU im. N.E Baumana. 2006. 664 pp.
SHiganov I. N., Kuryncev S. V. Sovremennye tendencii lazernoj svarki. Part I. Naukoemkie tekhnologii v mashinostroenii. 2015; 6: 35–42.
SHiganov I. N., Kuryncev S. V. Sovremennye tendencii lazernoj svarki. Part II. Naukoemkie tekhnologii v mashinostroenii. 2015; 9: 15–20.
Patent RU2678002 C1. Sposob soedineniya metallicheskogo materiala s kompozicionnym materialom lazernym luchom / Kuryncev S. V.
Kuryncev S. V., SHiganov I. N. Svarka austenitnoj stali s med’yu rasfokusirovannym izlucheniem volokonnogo lazera. Svarochnoe proizvodstvo. 2017; 4: 7–11.
Lukin M. A. Kontaktnaya stykovaya svarka oplavleniem paketa alyuminievyh listov so stal’nym sterzhnem. Svarochnoe proizvodstvo. 2020; 3: 38–43.
Frank S. Flux-free laser joining of aluminum and galvanized steel. Journal of Materials Processing Technology. 2015, 222: 365–372. DOI: 10.1016 / j.jmatprotec.2015.03.032.
Li LQ, Xia HB, Tan CW, Ma NS. Effect of groove shape on laser welding-brazing Al to steel. Journal of Materials Processing Technology. 2018; 252:573–81. DOI: 10.1016 / j.jmatprotec.2017.10.025.
Seffer O, Pfeifer R, Springer A, Kaierle S. Investigations on laser beam welding of different dissimilar joints of steel and aluminum alloys for automotive lightweight construction. Laser Assisted Net Shape Engineering 9 International Conference on Photonic Technologies Proceedings of the Lane 2016. 2016; 83:383–95. DOI: 10.1016 / j.phpro.2016.08.040.
Meco S, Cozzolino L, Ganguly S, Williams S, McPherson N. Laser welding of steel to aluminium: Thermal modelling and joint strength analysis. Journal of Materials Processing Technology. 2017;247:121–33. DOI: 10.1016 / j.jmatprotec.2017.04.002.
Cui L, Chen HX, Chen BX, He DY. Welding of Dissimilar Steel / Al Joints Using Dual-Beam Lasers with Side-by-Side Configuration. Metals. 2018; 8(12):21. DOI: 10.3390 / met8121017.
Lyuhter A. B., SHlegel’ A. N., Leont’ev A. A., Gusev D. S. Rezul’taty mekhanicheskih ispytanij korpusnyh elementov avtobusov, poluchennyh lazernoj svarkoj stal’nogo profilya St3 s alyuminievoj oblicovkoj AMg2M. Cvetnye metally. 2017; 10: 85–89.
Casalino G, Leo P, Mortello M, Perulli P, Varone A. Effects of Laser Offset and Hybrid Welding on Microstructure and IMC in Fe-Al Dissimilar Welding. Metals. 2017; 7(8). DOI: 10.3390 / met7080282.
Huang JK, He J, Yu XQ, Li CL, Fan D. The study of mechanical strength for fusion-brazed butt joint between aluminum alloy and galvanized steel by arc-assisted laser welding. Journal of Manufacturing Processes. 2017; 25:126–33. DOI: 10.1016 / j.jmapro.2016.11.014.
Nothdurft S, Prasanthan V, Denkena B, Breidenstein B, Grove T, Ohrdes H, et al. Surface Integrity of Laser Beam Welded Steel-Aluminium Alloy Hybrid Shafts after Turning. Metals. 2019; 9(2). DOI: 10.3390 / met9020134
Meco S, Ganguly S, Williams S, McPherson N. Design of laser welding applied to T joints between steel and aluminium. Journal of Materials Processing Technology. 2019; 268:132–9. DOI: 10.1016 / j.jmatprotec.2019.01.003.
Meng YF, Gong MC, Zhang S, Zhang YZ, Gao M. Effects of oscillating laser offset on microstructure and properties of dissimilar Al / steel butt-joint. Optics and Lasers in Engineering. 2020;128. DOI: 10.1016 / j.optlaseng.2020.106037.
ABOUT AUTHORS
Kuryntsev Sergey V., Candidate of Sciences (Economics), e-mail kuryntsev16@mail.ru, Kazan National Research Technical University named after A. N. Tupolev – KAI, Kazan, Russia.
Igor Nikolaevich Shiganov, Doctor of Technical Sciences, Professor, Moscow State Technical University named after N. E. Moscow, Russia.
Contributions of authors
Kuryntsev S. V. – idea, translation and analysis of material, work with graphic part, results processing. Shiganov I. N. – discussion, suggestions and comments, material analysis.
Conflict of interest
The authors declare no real or potential conflicts of interest.
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