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18 pages, 15610 KiB

Open AccessArticle

Improving Welding Penetration and Mechanical Properties via Activated-Flux Smearing by Tungsten Inert Gas Arc Welding

by Shiqi Yue, Yong Huang, Xiaoquan Yu, Jia Zhang, Yu Ni and Ding Fan

Metals 2023, 13(12), 2017; https://doi.org/10.3390/met13122017 - 15 Dec 2023

Viewed by 957

Abstract

For the welding process of thick-walled structural components in liquid rocket engines, the activated-flux TIG method can effectively address issues such as the formation of intermetallic phases in the weld seams, thereby enhancing mechanical performance. The present study investigates the activated-flux TIG welding [...] Read more.

For the welding process of thick-walled structural components in liquid rocket engines, the activated-flux TIG method can effectively address issues such as the formation of intermetallic phases in the weld seams, thereby enhancing mechanical performance. The present study investigates the activated-flux TIG welding technique on 10mm thick 1Cr21Ni5Ti duplex stainless steel plates. Various activated-flux, including -SiO₂, TiO₂, V₂O₅, NiO, MnO₂, CaO, AlCl₃, CaF₂, B₂O₃ Cr₂O₃, and Al₂O₃, were examined to understand their impact on the weld-bead geometry. The aim was to determine the optimal activator ratio for the effective welding of 1Cr21Ni5Ti duplex stainless steel. The weld-shift experiment confirmed that the deep penetration observed in flux-assisted welding is attributed to Marangoni convection in the molten pool. Comprehensive evaluations and analyses were performed on the microstructure and mechanical properties of the normal welded joint and the A-TIG welded joint. Finally, the study delves into a discussion on the factors influencing changes in the weld penetration, microstructure, and mechanical properties of the weld. Full article

(This article belongs to the Special Issue Microstructure and Mechanical Property Improvement of Welded Metal Joints)

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12 pages, 4220 KiB

Open AccessArticle

Microstructures and Electrical Resistivity of Aluminum–Copper Joints

by Jinchang Guo, Chunkai Li, Jianxiao Bian, Jianrui Zhang and Baolong Geng

Metals 2023, 13(8), 1474; https://doi.org/10.3390/met13081474 - 16 Aug 2023

Viewed by 955

Abstract

Using pulsed double electrode-gas metal arc welding, aluminum wires are joined to copper plates with fillers of different fractions of silicon. Two layers of different microstructures are formed near the Al-Cu interface: one consists of a hypoeutectic microstructure of α (Al) + Al [...] Read more.

Using pulsed double electrode-gas metal arc welding, aluminum wires are joined to copper plates with fillers of different fractions of silicon. Two layers of different microstructures are formed near the Al-Cu interface: one consists of a hypoeutectic microstructure of α (Al) + Al₂Cu, and the other consists of an intermetallic compound (IMC) of Al₂Cu. Increasing the heat input causes increases in the thicknesses of the IMC layer and the layer of the hypoeutectic microstructure. Si suppresses the growth of the IMC layer and assists the growth of the layer of the hypoeutectic microstructure. The effects of the interface microstructures and chemical compositions on the electric resistivity of the joints are analyzed. The electric resistivity of the joints increases with the increase in the thicknesses of the IMC layer and the layer of the hypoeutectic microstructure. The law of mixture is used to calculate the electric resistivity of the joints, which is in accordance with the experimental results. Full article

(This article belongs to the Special Issue Microstructure and Mechanical Property Improvement of Welded Metal Joints)

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14 pages, 5329 KiB

Open AccessArticle

Welding of Ti6Al4V and Al6082-T6 Alloys by a Scanning Electron Beam

by Angel Anchev, Darina Kaisheva, Georgi Kotlarski, Vladimir Dunchev, Borislav Stoyanov, Maria Ormanova, Milka Atanasova, Vladimir Todorov, Petya Daskalova and Stefan Valkov

Metals 2023, 13(7), 1252; https://doi.org/10.3390/met13071252 - 9 Jul 2023

Cited by 4 | Viewed by 947

Abstract

This work presents the results of an investigation into the influence of beam offset on the structure and mechanical properties of electron-beam-welded joints between Ti6Al4V and Al6082-T6 alloys. The experimental procedure involved the use of specific technological conditions: an accelerating voltage of 60 [...] Read more.

This work presents the results of an investigation into the influence of beam offset on the structure and mechanical properties of electron-beam-welded joints between Ti6Al4V and Al6082-T6 alloys. The experimental procedure involved the use of specific technological conditions: an accelerating voltage of 60 kV, an electron beam current of 35 mA, a specimen motion speed of 10 mm/s, and a beam offset of 0.5 mm towards both alloys, as well as welding without an offset. The phase composition of the joints was analyzed using X-ray diffraction (XRD). The microstructure and chemical composition of the seams were studied by scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX). The results obtained for the structure of the joints show that the beam offset has a significant influence on the structure. The microhardness was studied by means of the Vickers method. The results for the microstructure showed that the welding procedure without offset and with an offset towards the Ti alloy leads to inhomogeneous welded joints with a significant amount of intermetallics. The offset towards the Al alloy leads to the formation of a narrow area of TiAl₃ phase. The measured microhardness corresponds to the increased amount of intermetallics in the case of offset towards the Ti alloy, with which the highest values were presented (about 58% higher than with Ti6Al4V plate). The results obtained for tensile properties show that the offset to the Al6082-T6 alloy leads to the highest values of tensile strength (TS) and yield strength (YS), which are twice higher than in welding without offsetting of the electron beam. Full article

(This article belongs to the Special Issue Microstructure and Mechanical Property Improvement of Welded Metal Joints)

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12 pages, 6608 KiB

Open AccessArticle

The Effect of Cooling Temperature on Microstructure and Mechanical Properties of Al 6061-T6 Aluminum Alloy during Submerged Friction Stir Welding

by Kiran Wakchaure, Rakesh Chaudhari, Ajaykumar Thakur, Kishan Fuse, Luis Norberto Lopez de Lacalle and Jay Vora

Metals 2023, 13(7), 1159; https://doi.org/10.3390/met13071159 - 22 Jun 2023

Cited by 1 | Viewed by 1060

Abstract

Submerged friction stir welding (SFSW) is a new modification of friction stir welding. In this paper, 6 mm thick 6061Al-T6 alloy plates were welded using the friction stir technique under normal air and submerged water conditions at 108 mm/min welding speeds and a [...] Read more.

Submerged friction stir welding (SFSW) is a new modification of friction stir welding. In this paper, 6 mm thick 6061Al-T6 alloy plates were welded using the friction stir technique under normal air and submerged water conditions at 108 mm/min welding speeds and a rotational rate of 900 rpm. The cooling water temperature in SFSW varied at 0 °C, 35 °C, and 80 °C to clarify the effect of water temperature. The characteristic hourglass-shaped stir zone was observed in the macrostructure of all the samples. All the samples exhibited defect-free joints. The results revealed that the finer grain size of 2.43 μm was at 0 °C. The macrostructure of SFSW joints separated into the shoulder-driven zone and pin-driven zone due to the low-temperature difference between the environment and water media and the high heat absorption capacity of the water, which caused a more substantial cooling rate during water-submerged welded joints. The microhardness distribution of all the joints showed typical “W” shape characteristics. The microhardness for all submerged samples was higher than in normal air conditions due to the higher thermal cycling effect in submerged conditions. Improved dynamic recrystallization in the joint welded at 80 °C resulted in the highest tensile strength (~249 MPa) and microhardness (~95 HV). Full article

(This article belongs to the Special Issue Microstructure and Mechanical Property Improvement of Welded Metal Joints)

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12 pages, 6282 KiB

Open AccessArticle

Electron-Beam Welding of Titanium and Ti6Al4V Alloy

by Georgi Kotlarski, Darina Kaisheva, Maria Ormanova, Borislav Stoyanov, Vladimir Dunchev, Angel Anchev and Stefan Valkov

Metals 2023, 13(6), 1065; https://doi.org/10.3390/met13061065 - 1 Jun 2023

Cited by 4 | Viewed by 1916

Abstract

This work presents the results of the electron-beam welding of commercially pure α-Ti (CP-Ti) and Ti6Al4V (Ti64) alloys. The structure and mechanical properties of the formed welded joints were examined as a function of the power of the electron beam. The beam power [...] Read more.

This work presents the results of the electron-beam welding of commercially pure α-Ti (CP-Ti) and Ti6Al4V (Ti64) alloys. The structure and mechanical properties of the formed welded joints were examined as a function of the power of the electron beam. The beam power was set to P₁ = 2100 W, P₂ = 1500 W, and P₃ = 900 W, respectively. X-ray diffraction (XRD) experiments were performed in order to investigate the phase composition of the fabricated welded joints. The microstructure was examined by both optical microscopy, scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDX). The mechanical properties of the formed joints were studied using tensile test experiments and microhardness experiments. The results of the experiments were discussed concerning the influence of the beam power on the microstructure and the mechanical properties of the weld joints. Furthermore, the practical applicability of the present method for the welding of α-Ti and Ti64 was also discussed. Full article

(This article belongs to the Special Issue Microstructure and Mechanical Property Improvement of Welded Metal Joints)

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20 pages, 48910 KiB

Open AccessArticle

Investigation of the Mechanism of Powder Pool Coupled Activating TIG Welding

by Yong Huang, Boyang Wang, Jianhang Guo, Ding Fan and Shurong Yu

Metals 2023, 13(5), 830; https://doi.org/10.3390/met13050830 - 23 Apr 2023

Viewed by 1242

Abstract

As a highly effective welding method, PPCA-TIG (Powder Pool Coupled Activating Flux–Tungsten Inert Gas) welding aims to achieve automated activation of TIG welding through the use of suitable activating fluxes. However, due to the unique transitional behavior of activating elements, the mechanism of [...] Read more.

As a highly effective welding method, PPCA-TIG (Powder Pool Coupled Activating Flux–Tungsten Inert Gas) welding aims to achieve automated activation of TIG welding through the use of suitable activating fluxes. However, due to the unique transitional behavior of activating elements, the mechanism of PPCA-TIG is a little bit different from common activating TIG welding. In this research, a two-dimensional model is established to investigate the effect of four activating fluxes (TiO₂, SiO₂, MnO₂, CaF₂) on arc morphology and force. A series of welding experiments is performed to study the impact of the different activating elements on the molten pool. The results show that the increase in the penetration of TiO₂ is related to the high arc temperature and great arc force and electromagnetic force in the molten pool. The problem of the softening of 3003 aluminum alloy welded joints is solved. Other activating fluxes are less effective than TiO₂. The addition of calcium fluoride significantly affects penetration. The use of TiO₂, SiO₂ and MnO₂ changes the molten pool viscosity and affects the molten pool oscillation, thus affecting the weld quality. Full article

(This article belongs to the Special Issue Microstructure and Mechanical Property Improvement of Welded Metal Joints)

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14 pages, 3595 KiB

Open AccessArticle

The Al-Fe Intermetallic Compounds and the Atomic Diffusion Behavior at the Interface of Aluminum-Steel Welded Joint

by Yinglong Zhang, Tianxiang Zhao, Xiaoquan Yu and Jiankang Huang

Metals 2023, 13(2), 334; https://doi.org/10.3390/met13020334 - 7 Feb 2023

Cited by 6 | Viewed by 2282

Abstract

The formation of intermetallic compounds (IMC) at the Al/Fe interface determined the mechanical property of steel-aluminum welded joint. To understand the interfacial microstructure evolution and relate diffusion mechanism of atoms cross the Al/Fe interface, the effect of welding parameters on the interfacial IMC [...] Read more.

The formation of intermetallic compounds (IMC) at the Al/Fe interface determined the mechanical property of steel-aluminum welded joint. To understand the interfacial microstructure evolution and relate diffusion mechanism of atoms cross the Al/Fe interface, the effect of welding parameters on the interfacial IMC was studied, and the molecular dynamics method (MD) was used to simulate the diffusion process of Al and Fe atoms. Four temperatures (950 K, 1000 K, 1050 K, and 1100 K) were selected in the simulation model. The interfacial IMC are distributed in a laminar pattern, and their physical phases are mainly composed of Fe₂Al₅, controlling the Al/Fe atomic ratio of 5:2 in the IMC configuration, the Embedded Atom Method (EAM) potential is used to describe the interactions between Al and Fe atoms. In the Al-Fe system IMC conformation, the mean square displacement and diffusion (MSD) coefficient of Al atoms at different temperatures were small, and the main diffusion path is the Al atoms across the IMC conformation into the Fe crystal structure. The diffusion in the IMC conformation was mainly along the direction perpendicular to the interface. The diffusion mechanisms were mainly vacancy diffusion and interstitial diffusion mechanisms. Full article

(This article belongs to the Special Issue Microstructure and Mechanical Property Improvement of Welded Metal Joints)

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Graphical abstract

13 pages, 10695 KiB

Open AccessArticle

Analysis of Droplet Transfer and Arc Swing in “TIG + AC” Twin-Wire Cross Arc Additive Manufacturing

by Xueping Song, Zhuoxuan Li, Jiankang Huang, Ding Fan and Shurong Yu

Metals 2023, 13(1), 63; https://doi.org/10.3390/met13010063 - 26 Dec 2022

Cited by 3 | Viewed by 1519

Abstract

Twin-wire and arc additive manufacturing (T-WAAM) has potential advantages in improving deposition efficiency and manufacturing functionally graded materials (FGMs), thus attracting much attention. However, there are few studies on the droplet transfer mode of T-WAAM. This paper analyzes the droplet transfer mode and [...] Read more.

Twin-wire and arc additive manufacturing (T-WAAM) has potential advantages in improving deposition efficiency and manufacturing functionally graded materials (FGMs), thus attracting much attention. However, there are few studies on the droplet transfer mode of T-WAAM. This paper analyzes the droplet transfer mode and arc swing in the “TIG + AC” twin-wire cross-arc additive manufacturing by in-situ observation with high-speed photography, revealing what factors influence the T-WAAM on deposition shaping the quality and what are the key mechanisms for process stability. Experiments show that with the main arc current provided by TIG 100 A and the twin-wire AC arc current 10 A, three different droplet transfer modes, namely the “free transfer + free transfer, bridge transfer + free transfer, bridge transfer + bridge transfer,” can be observed with the twin wires under different feeding speeds. The corresponding deposition and arc swing are quite different in quality. Through comparative analysis, it is found that the frequent extinguishment and ignition of the arc between electrode wires is the main factor for the instability in the additive manufacturing process. The “bridge transfer + free transfer” mode can obtain a large arc swing angle and a stable deposition, in which the cross arc has a significant stirring effect on the molten pool, and the deposition shape is well-made. Full article

(This article belongs to the Special Issue Microstructure and Mechanical Property Improvement of Welded Metal Joints)

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14 pages, 10976 KiB

Open AccessArticle

Microstructure and Mechanical Properties of Arc Zone and Laser Zone of TC4 Titanium Alloy Laser–TIG Hybrid Welded Joint

by Hao Fan, Peng Zhou, Jie Li, Jiankang Huang, Yu Ni and Yuanyuan Hui

Metals 2022, 12(11), 1854; https://doi.org/10.3390/met12111854 - 30 Oct 2022

Cited by 3 | Viewed by 1434

Abstract

As a high-efficiency and high-quality welding technology, laser-tungsten inert gas (laser–TIG) hybrid welding has been widely used in the aerospace and marine equipment industries. Through laser–TIG hybrid welding of TC4 titanium alloy, the effect of the current on the weld formation, the microstructure [...] Read more.

As a high-efficiency and high-quality welding technology, laser-tungsten inert gas (laser–TIG) hybrid welding has been widely used in the aerospace and marine equipment industries. Through laser–TIG hybrid welding of TC4 titanium alloy, the effect of the current on the weld formation, the microstructure and mechanical properties of the arc zone, and the laser zone was studied. The results show that the molten pool in the arc zone will flow periodically, and the flow becomes more intense with an increase in the current, which will result in a finer grain size in the arc zone than in the laser zone, having the effect of eliminating pores. The spacing of the α′ martensite beams in the laser zone is narrower, with an average spacing of 0.41 μm. The β phase increases gradually with the increase in the current, which will lead to a downward trend in the average hardness of both zones. The average hardness value of the laser zone, containing more α′ martensite and less β phase, is slightly higher than that of the arc zone. The hardness uniformity of the laser zone is also significantly better than that of the arc zone. The tensile strength of the joint shows a trend of increasing first and then decreasing, and the joint with I = 50 A presented the highest tensile strength of 957.3 MPa, approaching 100% of the base metal, and fractured in the fusion zone. Full article

(This article belongs to the Special Issue Microstructure and Mechanical Property Improvement of Welded Metal Joints)

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Review

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22 pages, 11447 KiB

Open AccessReview

Ultrasonic Welding of Aluminum to Steel: A Review

by Changxin Zhang, Huan Li, Qianxi Liu, Chaowang Huang and Kang Zhou

Metals 2023, 13(1), 29; https://doi.org/10.3390/met13010029 - 22 Dec 2022

Cited by 8 | Viewed by 2801

Abstract

As a solid-state bonding technology, ultrasonic welding (USW) has the characteristics of green energy saving and environmental friendliness. It is more suitable for joining dissimilar metals than other welding technologies. The aluminum-to-steel USWed joint has been widely used in the automotive and aviation [...] Read more.

As a solid-state bonding technology, ultrasonic welding (USW) has the characteristics of green energy saving and environmental friendliness. It is more suitable for joining dissimilar metals than other welding technologies. The aluminum-to-steel USWed joint has been widely used in the automotive and aviation industries. Currently, there is no review literature report on aluminum-to-steel USW. The main physical phenomena of the USW process include interface temperature increase, ultrasonic softening, plastic deformation, formation and growth of the IMCs, and dynamic recrystallization. Hence, the microstructures and mechanical properties of aluminum-alloy-to-low-carbon-steel, aluminum-alloy-to-stainless steel, and aluminum-alloy-to-galvanized-steel-joints by USW are reviewed. Moreover, the effect of interface temperature, interface plastic deformation, and interface macrostructure and microstructure is explored. Lastly, tensile-shear and fatigue strength of joints and numerical simulation of the USW process are also discussed. In addition, some new application types of aluminum-to-steel USW are introduced. Finally, the future trends of aluminum-to-steel USW with guidance are provided. Full article

(This article belongs to the Special Issue Microstructure and Mechanical Property Improvement of Welded Metal Joints)

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