Science, Characterization and Technology of Joining and Welding

A special issue of Metals (ISSN 2075-4701). This special issue belongs to the section "Metal Casting, Forming and Heat Treatment".

Deadline for manuscript submissions: closed (31 December 2018) | Viewed by 83408

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Special Issue Editor


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Guest Editor
Department of Mechanical Engineering, College of Engineering and Mine, University of North Dakota, Grand Forks, North Dakota, USA
Interests: friction stir welding and processing; length-scale mechanical properties (i.e., nanoindentation); metal additive manufacturing; thermomechanical processing

Special Issue Information

Dear Colleagues,

Joining, i.e., welding, is an essential requirement in manufacturing and assembly processes and is classified as a secondary manufacturing process. This Special Issue of Metals invites technical and review papers on, but not limited to, different aspects of joining and welding, including welding technologies (i.e., fusion based welding and solid-state welding), characterization, metallurgy and materials science, quality control, design and numerical simulation. This Special Issue also includes the joining of different materials, including metal and non-metals (polymers and composites). Papers on other methods of joining, other than welding, including soldering, brazing, adhesive bonding, accumulative roll bonding, etc., are also welcomed in this Special Issue.

Prof. Meysam Haghshenas
Guest Editor

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Keywords

  • Welding
  • Joining
  • Soldering
  • Brazing
  • Adhesive bonding
  • Welding metallurgy
  • Assembly
  • Welding characterization
  • Solid-state welding

Published Papers (17 papers)

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Research

13 pages, 8822 KiB  
Article
Mechanical and Microstructural Investigations of the Laser Welding of Different Zinc-Coated Steels
by Eva Zdravecká and Ján Slota
Metals 2019, 9(1), 91; https://doi.org/10.3390/met9010091 - 16 Jan 2019
Cited by 15 | Viewed by 3533
Abstract
Tailor welded blanks (TWB) represent an anisotropic and non-homogenous material. The knowledge of the mechanical properties and microstructure of the fusion zone and heat-affected zone (HAZ) obtained with laser welding is essential to ensure the reliability of the process. In this paper, laser-welded [...] Read more.
Tailor welded blanks (TWB) represent an anisotropic and non-homogenous material. The knowledge of the mechanical properties and microstructure of the fusion zone and heat-affected zone (HAZ) obtained with laser welding is essential to ensure the reliability of the process. In this paper, laser-welded hot-dip Zn-coated low carbon microalloyed steels with different thickness and mechanical properties were used. The mechanical properties of the laser-welded blanks were determined by tensile tests and formability by Erichsen cupping tests. In addition, the pore formation during the laser welding process was analyzed. The microstructural analysis confirmed the formation of the favorable structure of the weld metal and the heat-affected zone without the presence of martensite. The obtained results showed that it is possible to produce TWBs with suitable mechanical properties by laser welding. Full article
(This article belongs to the Special Issue Science, Characterization and Technology of Joining and Welding)
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15 pages, 10183 KiB  
Article
Optimization of Process Parameters for Friction Stir Welding of Aluminum and Copper Using the Taguchi Method
by Nima Eslami, Yannik Hischer, Alexander Harms, Dennis Lauterbach and Stefan Böhm
Metals 2019, 9(1), 63; https://doi.org/10.3390/met9010063 - 10 Jan 2019
Cited by 28 | Viewed by 3866
Abstract
Producing joints of aluminum and copper by means of fusion welding is a challenging task. However, the results of various studies have proven the potential of friction stir welding (FSW) for manufacturing aluminum-copper joints. Despite the proven feasibility, there is currently no series [...] Read more.
Producing joints of aluminum and copper by means of fusion welding is a challenging task. However, the results of various studies have proven the potential of friction stir welding (FSW) for manufacturing aluminum-copper joints. Despite the proven feasibility, there is currently no series application in automotive industry to produce aluminum-copper joints for electrical contacts by means of FSW. To make FSW as efficient as possible for large-scale production, maximized welding speed is desired. Taking this into account, this paper presents results of a parametric investigation, the objective of which was to increase the welding speed for FSW of aluminum and copper in comparison to welding speeds that are considered to be state of the art. Taguchi method was used to design an experimental plan and target figures of the investigations were the resultant tensile strengths and electrical resistances. Dependencies between input parameters and target figures were determined systematically. The optimal welding parameters, at which joints failed in the weaker aluminum material, included a welding speed of 700 mm/min. Consequently, it could be shown that joints with a performance similar to those of the base materials can be obtained using significantly higher welding speeds than reported in the relevant literature. Full article
(This article belongs to the Special Issue Science, Characterization and Technology of Joining and Welding)
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10 pages, 3902 KiB  
Article
Diffusion Bonding of Ti2AlNb Alloy and High-Nb-Containing TiAl Alloy: Interfacial Microstructure and Mechanical Properties
by Hong Bian, Yuzhen Lei, Wei Fu, Shengpeng Hu, Xiaoguo Song and Jicai Feng
Metals 2018, 8(12), 1061; https://doi.org/10.3390/met8121061 - 14 Dec 2018
Cited by 14 | Viewed by 3272
Abstract
In this study, reliable Ti2AlNb/high-Nb-containing TiAl alloy (TAN) joints were achieved by diffusion bonding. The effects of bonding temperature and holding time on the interfacial microstructure and mechanical properties were fully investigated. The interfacial structure of joints bonded at various temperatures [...] Read more.
In this study, reliable Ti2AlNb/high-Nb-containing TiAl alloy (TAN) joints were achieved by diffusion bonding. The effects of bonding temperature and holding time on the interfacial microstructure and mechanical properties were fully investigated. The interfacial structure of joints bonded at various temperatures and holding times was characterized by scanning electron microscopy (SEM), energy dispersive spectrometer (EDS) and X-ray diffraction (XRD). The results show that the typical microstructure of the Ti2AlNb substrate/O phase/Al(Nb,Ti)2 + Ti3Al/Ti3Al/TAN substrate was obtained at 970 °C for 60 min under a pressure of 5 MPa. The formation of the O phase was earlier than the Al(Nb,Ti)2 phase when bonding temperature was relatively low. When bonding temperature was high enough, the Al(Nb,Ti)2 phase appeared earlier than the O phase. With the increase of bonding temperature and holding time, the Al(Nb,Ti)2 phase decomposed gradually. As the same time, continuous O phase layers became discontinuous and the Ti3Al phase coarsened. The maximum bonding strength of 66.1 MPa was achieved at 970 °C for 120 min. Full article
(This article belongs to the Special Issue Science, Characterization and Technology of Joining and Welding)
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18 pages, 26077 KiB  
Article
A New Approach to Simulate HSLA Steel Multipass Welding through Distributed Point Heat Sources Model
by Dario Magno Batista Ferreira, Antonio do Nascimento Silva Alves, Rubelmar Maia de Azevedo Cruz Neto, Thiago Ferreira Martins and Sérgio Duarte Brandi
Metals 2018, 8(11), 951; https://doi.org/10.3390/met8110951 - 15 Nov 2018
Cited by 11 | Viewed by 4503
Abstract
Mechanical properties of welded joints depend on the way heat flows through the welding passes. In multipass welding the reheating of the heat affected zone (HAZ) can form local brittle zones that need to be delimited for evaluation. The difficulty lies in the [...] Read more.
Mechanical properties of welded joints depend on the way heat flows through the welding passes. In multipass welding the reheating of the heat affected zone (HAZ) can form local brittle zones that need to be delimited for evaluation. The difficulty lies in the choice of a model that can simulate multipass welding. This study evaluated Rosenthal’s Medium Thick Plate (MTP) and the Distributed heat Sources (DHS) of Mhyr and Gröng models. Two assumptions were considered for both models: constant and temperature-dependent physical properties. It was carried out on a multipass welding of an API 5L X80 tube, with 1016 mm (42″) external diameter, 16 mm thick and half V-groove bevel, in the 3G up position. The root pass was welded with Gas Metal Arc Welding (GMAW) process with controlled short-circuit transfer. The Flux Cored Arc Welding (FCAW) process was used in the filling and finishing passes, using filler metal E111T1-K3M-JH4. The evaluation criteria used were overlapping the simulated isotherms on the marks revealed in the macrographs and the comparison between the experimental thermal cycle and those simulated by the proposed models. The DHS model with the temperature-dependent properties presented the best results and simulated with accuracy the HAZ of root and second welding passes. In this way, it was possible to delimit the HAZ heated sub-regions. Full article
(This article belongs to the Special Issue Science, Characterization and Technology of Joining and Welding)
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14 pages, 8188 KiB  
Article
Study on the Effect of Energy-Input on the Joint Mechanical Properties of Rotary Friction-Welding
by Guilong Wang, Jinglong Li, Weilong Wang, Jiangtao Xiong and Fusheng Zhang
Metals 2018, 8(11), 908; https://doi.org/10.3390/met8110908 - 06 Nov 2018
Cited by 12 | Viewed by 3286
Abstract
The objective of the present study is to investigate the effect of energy-input on the mechanical properties of a 304 stainless-steel joint welded by continuous-drive rotary friction-welding (RFW). RFW experiments were conducted over a wide range of welding parameters (welding pressure: 25–200 MPa, [...] Read more.
The objective of the present study is to investigate the effect of energy-input on the mechanical properties of a 304 stainless-steel joint welded by continuous-drive rotary friction-welding (RFW). RFW experiments were conducted over a wide range of welding parameters (welding pressure: 25–200 MPa, rotation speed: 500–2300 rpm, welding time: 4–20 s, and forging pressure: 100–200 MPa). The results show that the energy-input has a significant effect on the tensile strength of RFW joints. With the increase of energy-input, the tensile strength rapidly increases until reaching the maximum value and then slightly decreases. An empirical model for energy-input was established based on RFW experiments that cover a wide range of welding parameters. The accuracy of the model was verified by extra RFW experiments. In addition, the model for optimal energy-input of different forging pressures was obtained. To verify the accuracy of the model, the optimal energy-input of a 170 MPa forging pressure was calculated. Three RFW experiments in which energy-input was equal to the calculated value were made. The joints’ tensile strength coefficients were 90%, 93%, and 96% respectively, which proved that the model is accurate. Full article
(This article belongs to the Special Issue Science, Characterization and Technology of Joining and Welding)
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16 pages, 7850 KiB  
Article
Dissimilar Materials Joining of Carbon Fiber Polymer to Dual Phase 980 by Friction Bit Joining, Adhesive Bonding, and Weldbonding
by Yong Chae Lim, Hoonmo Park, Junho Jang, Jake W. McMurray, Bradly S. Lokitz, Jong Kahk Keum, Zhenggang Wu and Zhili Feng
Metals 2018, 8(11), 865; https://doi.org/10.3390/met8110865 - 24 Oct 2018
Cited by 12 | Viewed by 5183
Abstract
In the present work, joining of a carbon fiber-reinforced polymer and dual phase 980 steel was studied using the friction bit joining, adhesive bonding, and weldbonding processes. The friction bit joining process was optimized for the maximum joint strength by varying the process [...] Read more.
In the present work, joining of a carbon fiber-reinforced polymer and dual phase 980 steel was studied using the friction bit joining, adhesive bonding, and weldbonding processes. The friction bit joining process was optimized for the maximum joint strength by varying the process parameters. Then, the adhesive bonding and weld bonding (friction bit joining plus adhesive bonding) processes were further developed. Lap shear tensile and cross-tension testing were used to assess the joint integrity of each process. Fractured specimens were compared for the individual processes. The microstructures in the joining bit ranged from tempered martensite to fully martensite in the cross-section view of friction bit-joined specimens. Additionally, the thermal decomposition temperature of the as-received carbon fiber composite was studied by thermogravimetric analysis. Fourier-transform infrared–attenuated total reflectance spectroscopy and X-ray diffraction measurements showed minimal variations in the absorption peak and diffraction peak patterns, indicating insignificant thermal degradation of the carbon fiber matrix due to friction bit joining. Full article
(This article belongs to the Special Issue Science, Characterization and Technology of Joining and Welding)
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17 pages, 7218 KiB  
Article
Ultrasonic Inspection of a 9% Ni Steel Joint Welded with Ni-based Superalloy 625: Simulation and Experimentation
by João Da Cruz Payão Filho, Elisa Kimus Dias Passos, Rodrigo Stohler Gonzaga, Ramon Fonseca Ferreira, Daniel Drumond Santos and Diego Russo Juliano
Metals 2018, 8(10), 787; https://doi.org/10.3390/met8100787 - 02 Oct 2018
Cited by 9 | Viewed by 5058
Abstract
The ultrasonic inspection of thick-walled welded joint with austenitic weld metal has proven to be a challenge due to its anisotropic microstructure that can promote ultrasonic waves attenuation. This work aimed to optimize the phased array ultrasonic inspection of the thick-walled joint of [...] Read more.
The ultrasonic inspection of thick-walled welded joint with austenitic weld metal has proven to be a challenge due to its anisotropic microstructure that can promote ultrasonic waves attenuation. This work aimed to optimize the phased array ultrasonic inspection of the thick-walled joint of a 9% Ni steel pipe welded with Ni-based superalloy 625. The development was carried out by CIVA numeric simulation to preview the beam behavior during the inspection of GTAW (Gas Tungsten Arc Welding)/SMAW (Shielded Metal Arc Welding) joint with anisotropic weld metal. To validate the simulation results, experimental tests were performed with a phased array transducer using longitudinal waves on a calibration block withdrawn from the joint. The configuration of low frequency (2.25 MHz), 16 active elements and a scanning angle of 48° ensured the inspection of the entire joint and the computational simulation proved to be essential for the success of the inspection. Full article
(This article belongs to the Special Issue Science, Characterization and Technology of Joining and Welding)
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10 pages, 2712 KiB  
Article
Thermal Spray Coatings as an Adhesion Promoter in Metal/FRP Joints
by Thomas Lindner, Erik Saborowski, Mario Scholze, Benjamin Zillmann and Thomas Lampke
Metals 2018, 8(10), 769; https://doi.org/10.3390/met8100769 - 27 Sep 2018
Cited by 8 | Viewed by 3580
Abstract
In this study, various structuring methods for creating adhesion by mechanical interlocking in the interface of metal/FRP (fiber-reinforced polymer) joints are investigated. A novel processing route using thermal spray coatings as additive structure is presented. Different coating systems are first assessed by axial [...] Read more.
In this study, various structuring methods for creating adhesion by mechanical interlocking in the interface of metal/FRP (fiber-reinforced polymer) joints are investigated. A novel processing route using thermal spray coatings as additive structure is presented. Different coating systems are first assessed by axial loading tests with spray-coated plungers for the evaluation of the additive layer adhesion on the metallic base material. Additional microstructures, produced by different abrasive processes (corundum blasting, laser structuring, and fine milling) are compared with the additive structures. All surface structures are characterized by electron microscopy for two sheet materials: DC06 and AA6016-T4. The abrasive structures show a significant material dependence, while the selected coating system offers the adjustment to different base materials by an independent surface layer. The structured metal sheets were further joined to glass-fiber-reinforced polyamide 6 (PA6) by hot pressing to evaluate the interface properties in tensile shear tests. The results confirm a suitability of thermal spray coatings for providing a high bonding strength in metal/FRP joints for both investigated metallic substrate materials. Full article
(This article belongs to the Special Issue Science, Characterization and Technology of Joining and Welding)
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15 pages, 7457 KiB  
Article
Determining Material Data for Welding Simulation of Presshardened Steel
by Jonny Kaars, Peter Mayr and Kurt Koppe
Metals 2018, 8(10), 740; https://doi.org/10.3390/met8100740 - 20 Sep 2018
Cited by 5 | Viewed by 3571
Abstract
In automotive body-in-white production, presshardened 22MnB5 steel is the most widely used ultra-high-strength steel grade. Welding is the most important faying technique for this steel type, as other faying technologies often cannot deliver the same strength-to-cost ratio. In order to conduct precise numerical [...] Read more.
In automotive body-in-white production, presshardened 22MnB5 steel is the most widely used ultra-high-strength steel grade. Welding is the most important faying technique for this steel type, as other faying technologies often cannot deliver the same strength-to-cost ratio. In order to conduct precise numerical simulations of the welding process, flow stress curves and thermophysical properties from room temperature up to the melting point are required. Sheet metal parts made out of 22MnB5 are welded in a presshardened, that is, martensitic state. On the contrary, only flow stress curves for soft annealed or austenitized 22MnB5 are available in the literature. Available physical material data does not cover the required temperature range or is not available at all. This work provides experimentally determined hot-flow stress curves for rapid heating of 22MnB5 from the martensitic state. The data is complemented by a comprehensive set of thermophysical data of 22MnB5 between room temperature and melting. Materials simulation methods as well as a critical literature review were employed to obtain sound thermophysical data. A comparison of the numerically computed nugget growth curve in spot welding with experimental welding results ensures the validity of the hot-flow stress curves and thermophysical data presented. Full article
(This article belongs to the Special Issue Science, Characterization and Technology of Joining and Welding)
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13 pages, 4977 KiB  
Article
Characteristics of Welding and Arc Pressure in the Plasma–TIG Coupled Arc Welding Process
by Bo Wang, Xun-Ming Zhu, Hong-Chang Zhang, Hong-Tao Zhang and Ji-Cai Feng
Metals 2018, 8(7), 512; https://doi.org/10.3390/met8070512 - 03 Jul 2018
Cited by 14 | Viewed by 7083
Abstract
In this article, a novel hybrid welding process called plasma-TIG (Tungsten Inert Gas welding) coupled arc welding was proposed to improve the efficiency and quality of welding by utilizing the full advantage of plasma and TIG welding processes. The two arcs of plasma [...] Read more.
In this article, a novel hybrid welding process called plasma-TIG (Tungsten Inert Gas welding) coupled arc welding was proposed to improve the efficiency and quality of welding by utilizing the full advantage of plasma and TIG welding processes. The two arcs of plasma and TIG were pulled into each other into one coupled arc under the effect of Lorentz force and plasma flow force during welding experiments. The arc behavior of coupled arc was studied by means of its arc profile, arc pressure and arc force conditions. The coupled arc pressure distribution measurements were performed. The effects of welding conditions on coupled arc pressure were evaluated and the maximum coupled arc pressure was improved compared with single-plasma arc and single-TIG arc. It was found that the maximum arc pressure was mainly determined by plasma arc current and plasma gas flow. Compared with traditional hybrid welding method, the efficiency was obviously higher and the welding heat-input was lower. The epitaxial solidification of the weld was inhibited, the tensile strength of the welded joints was higher. According to the results, the proposed coupled arc welding process has both advantages of plasma arc and TIG method, and it has a broad application prospect. Full article
(This article belongs to the Special Issue Science, Characterization and Technology of Joining and Welding)
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13 pages, 3264 KiB  
Article
Liquation Cracking in the Heat-Affected Zone of IN738 Superalloy Weld
by Kai-Cheng Chen, Tai-Cheng Chen, Ren-Kae Shiue and Leu-Wen Tsay
Metals 2018, 8(6), 387; https://doi.org/10.3390/met8060387 - 27 May 2018
Cited by 40 | Viewed by 6834
Abstract
The main scope of this study investigated the occurrence of liquation cracking in the heat-affected zone (HAZ) of IN738 superalloy weld, IN738 is widely used in gas turbine blades in land-based power plants. Microstructural examinations showed considerable amounts of γ’ uniformly precipitated in [...] Read more.
The main scope of this study investigated the occurrence of liquation cracking in the heat-affected zone (HAZ) of IN738 superalloy weld, IN738 is widely used in gas turbine blades in land-based power plants. Microstructural examinations showed considerable amounts of γ’ uniformly precipitated in the γ matrix. Electron probe microanalysis (EPMA) maps showed the γ-γ’ colonies were rich in Al and Ti, but lean in other alloy elements. Moreover, the metal carbides (MC), fine borides (M3B2 and M5B3), η-Ni3Ti, σ (Cr-Co) and lamellar Ni7Zr2 intermetallic compounds could be found at the interdendritic boundaries. The fracture morphologies and the corresponding EPMA maps confirmed that the liquation cracking in the HAZ of the IN738 superalloy weld resulted from the presence of complex microconstituents at the interdendritic boundaries. Full article
(This article belongs to the Special Issue Science, Characterization and Technology of Joining and Welding)
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17 pages, 9402 KiB  
Article
Characterizing the Soldering Alloy Type In–Ag–Ti and the Study of Direct Soldering of SiC Ceramics and Copper
by Roman Koleňák, Igor Kostolný, Jaromír Drápala, Martin Sahul and Ján Urminský
Metals 2018, 8(4), 274; https://doi.org/10.3390/met8040274 - 16 Apr 2018
Cited by 16 | Viewed by 5712
Abstract
The aim of the research was to characterize the soldering alloy In–Ag–Ti type, and to study the direct soldering of SiC ceramics and copper. The In10Ag4Ti solder has a broad melting interval, which mainly depends on its silver content. The liquid point of [...] Read more.
The aim of the research was to characterize the soldering alloy In–Ag–Ti type, and to study the direct soldering of SiC ceramics and copper. The In10Ag4Ti solder has a broad melting interval, which mainly depends on its silver content. The liquid point of the solder is 256.5 °C. The solder microstructure is composed of a matrix with solid solution (In), in which the phases of titanium (Ti3In4) and silver (AgIn2) are mainly segregated. The tensile strength of the solder is approximately 13 MPa. The strength of the solder increased with the addition of Ag and Ti. The solder bonds with SiC ceramics, owing to the interaction between active In metal and silicon infiltrated in the ceramics. XRD analysis has proven the interaction of titanium with ceramic material during the formation of the new minority phases of titanium silicide—SiTi and titanium carbide—C5Ti8. In and Ag also affect bond formation with the copper substrate. Two new phases were also observed in the bond interphase—(CuAg)6In5 and (AgCu)In2. The average shear strength of a combined joint of SiC–Cu, fabricated with In10Ag4Ti solder, was 14.5 MPa. The In–Ag–Ti solder type studied possesses excellent solderability with several metallic and ceramic materials. Full article
(This article belongs to the Special Issue Science, Characterization and Technology of Joining and Welding)
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11 pages, 9313 KiB  
Article
The Role of a MDP/VBATDT-Primer Composition on Resin Bonding to Zirconia
by Anuj Aggarwal and Grace M. De Souza
Metals 2018, 8(4), 247; https://doi.org/10.3390/met8040247 - 07 Apr 2018
Cited by 2 | Viewed by 5049
Abstract
Yttria-tetragonal zirconia polycrystal (Y-TZP) is a difficult substrate to bond to due to the absence of a glass phase and the material’s chemical inertness. This study evaluated the effect of two monomers for metal, MDP (10-methacryloyloxydecyl dihydrogen phosphate) and VBATDT (6-(4-vinylbenzyl-n-propyl)amino-1,3,5-trizaine-2,4-dithiol) on bond [...] Read more.
Yttria-tetragonal zirconia polycrystal (Y-TZP) is a difficult substrate to bond to due to the absence of a glass phase and the material’s chemical inertness. This study evaluated the effect of two monomers for metal, MDP (10-methacryloyloxydecyl dihydrogen phosphate) and VBATDT (6-(4-vinylbenzyl-n-propyl)amino-1,3,5-trizaine-2,4-dithiol) on bond strength to Y-TZP. Seven combinations with different concentrations of MDP and VBATDT-monomers (0.0, 0.1, 0.5, or 1.0 wt %) in acetone solution were developed and applied to the surface of Y-TZP slabs, which were bonded to composite resin substrates using a resin cement under standard loading. Non-primed samples were used as controls. Bonded specimens were cut for microtensile testing and tested after either 48 h or 180 days in water storage at room temperature. All samples from control group (no primer) and MV5 group (0% MDP/0.5% VBATDT) debonded spontaneously. Two-way ANOVA showed that the primer had a significant effect (p < 0.001) on bond strength to zirconia, whilst storage time did not (p = 0.203). Tukey HSD (honest significant difference) test indicated that groups with at least 0.5% of each monomer resulted in higher initial bond strength values. Although chemical bonding to zirconia is credited to MDP, a correct balance between MDP and VBATDT may imply in better bond strength results. The minimum concentration of each monomer should not be lower than 0.5 wt %. Full article
(This article belongs to the Special Issue Science, Characterization and Technology of Joining and Welding)
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14 pages, 9634 KiB  
Article
Microstructural Characteristics and m23c6 Precipitate Behavior of the Course-Grained Heat-Affected Zone of T23 Steel without Post-Weld Heat Treatment
by Seong-Hyeong Lee, Hye-Sung Na, Kyong-Woon Lee, Youngson Choe and Chung Yun Kang
Metals 2018, 8(3), 170; https://doi.org/10.3390/met8030170 - 09 Mar 2018
Cited by 11 | Viewed by 5420
Abstract
The microstructural characteristics of a simulated heat-affected zone (HAZ) in SA213-T23 (2.25Cr-1.6W steel) used for boiler tubes employed in thermal power plants were investigated using nital, alkaline sodium picrate, and Murakami’s etchants. In order to investigate the microstructure formation process of the HAZ [...] Read more.
The microstructural characteristics of a simulated heat-affected zone (HAZ) in SA213-T23 (2.25Cr-1.6W steel) used for boiler tubes employed in thermal power plants were investigated using nital, alkaline sodium picrate, and Murakami’s etchants. In order to investigate the microstructure formation process of the HAZ in the welding process, simulated HAZ specimens were fabricated at intervals of 100 °C for peak temperatures between 950 and 1350 °C, and the microstructural features and precipitate behavior at various peak temperatures were observed. The alkaline-sodium-picrate-etched microstructures exhibited a black dot or band, which was not observed in the natal-etched microstructure. As the temperature increased from 950 to 1350 °C, the black dot and band became wider and thicker. Experimental analyses using an electron probe micro-analyzer, electron backscatter diffraction, and transmission electron microscopy revealed the appearance of austenite in the black dot region at a peak temperature of 950 °C; its amount increased up to a peak temperature of 1050 °C and thereafter decreased as the peak temperature further increased. The amount of M23C6 decreased with an increase in peak temperature. Based on these results, we investigated the behaviors of austenite and M23C6 as functions of the peak temperature. Full article
(This article belongs to the Special Issue Science, Characterization and Technology of Joining and Welding)
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10 pages, 4758 KiB  
Article
The Application of 40Ti-35Ni-25Nb Filler Foil in Brazing Commercially Pure Titanium
by Shan-Bo Wang, Chuan-Sheng Kao, Leu-Wen Tsay and Ren-Kae Shiue
Metals 2018, 8(3), 154; https://doi.org/10.3390/met8030154 - 01 Mar 2018
Cited by 3 | Viewed by 3245
Abstract
The clad ternary 40Ti-35Ni-25Nb (wt %) foil has been applied in brazing commercially pure titanium (CP-Ti). The wavelength dispersive spectroscope (WDS) was utilized for quantitative chemical analyses of various phases/structures, and electron back scattered diffraction (EBSD) was used for crystallographic analyses in the [...] Read more.
The clad ternary 40Ti-35Ni-25Nb (wt %) foil has been applied in brazing commercially pure titanium (CP-Ti). The wavelength dispersive spectroscope (WDS) was utilized for quantitative chemical analyses of various phases/structures, and electron back scattered diffraction (EBSD) was used for crystallographic analyses in the brazed joint. The microstructure of brazed joint relies on the Nb and Ni distributions across the joint. For the β-Ti alloyed with high Nb and low Ni contents, the brazed zone (BZ), consisting of the stabilized β-Ti at room temperature. In contrast, eutectoid decomposition of the β-Ti into Ti2Ni and α-Ti is widely observed in the transition zone (TZ) of the joint. Although average shear strengths of joints brazed at different temperatures are approximately the same level, their standard deviations decreased with increasing the brazing temperature. The presence of inherent brittle Ti2Ni intermetallics results in higher standard deviation in shear test. Because the Ni content is lowered in TZ at a higher brazing temperature, the amount of eutectoid is decreased in TZ. The fracture location is changed from TZ into BZ mixed with α and β-Ti. Full article
(This article belongs to the Special Issue Science, Characterization and Technology of Joining and Welding)
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15 pages, 15727 KiB  
Article
Investigation on the Effect of Tool Pin Profiles on Mechanical and Microstructural Properties of Friction Stir Butt and Scarf Welded Aluminium Alloy 6063
by Pankul Goel, Arshad Noor Siddiquee, Noor Zaman Khan, Mohd Azmal Hussain, Zahid A. Khan, Mustufa Haider Abidi and Abdulrahman Al-Ahmari
Metals 2018, 8(1), 74; https://doi.org/10.3390/met8010074 - 19 Jan 2018
Cited by 36 | Viewed by 6835
Abstract
In the present study, friction stir welding (FSW) of butt and scarf joints of Al 6063-T6 were investigated. Five different tool pin profiles (cylindrical, tapered cylindrical, square, triangular, and hexagonal) were applied for performing welding. Scarf joint, being a new joint configuration, was [...] Read more.
In the present study, friction stir welding (FSW) of butt and scarf joints of Al 6063-T6 were investigated. Five different tool pin profiles (cylindrical, tapered cylindrical, square, triangular, and hexagonal) were applied for performing welding. Scarf joint, being a new joint configuration, was used and effect of pin profiles was investigated on this type of joint configuration. The effect of pin profiles on microstructure, micro-hardness, impact and tensile properties of friction stir welded Al 6063-T6 was investigated. Scanning electron and optical microscopy were employed to characterize the different zones of welded joints. A thorough discussion on correlation between mechanical properties and microstructure has been made. In addition, the formation of various defects during the FSW was discussed with the help of fractography of the fractured surfaces. Full article
(This article belongs to the Special Issue Science, Characterization and Technology of Joining and Welding)
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16 pages, 14068 KiB  
Article
Mechanism of Solder Joint Cracks in Anisotropic Conductive Films Bonding and Solutions: Delaying Hot-Bar Lift-Up Time and Adding Silica Fillers
by Shuye Zhang, Ming Yang, Mingliang Jin, Wen-Can Huang, Tiesong Lin, Peng He, Panpan Lin and Kyung-Wook Paik
Metals 2018, 8(1), 42; https://doi.org/10.3390/met8010042 - 09 Jan 2018
Cited by 16 | Viewed by 6400
Abstract
Micron sizes solder metallurgical joints have been applied in a thin film application of anisotropic conductive film and benefited three general advantages, such as lower joint resistance, higher power handling capability, and reliability, when compared with pressure based contact of metal conductor balls. [...] Read more.
Micron sizes solder metallurgical joints have been applied in a thin film application of anisotropic conductive film and benefited three general advantages, such as lower joint resistance, higher power handling capability, and reliability, when compared with pressure based contact of metal conductor balls. Recently, flex-on-board interconnection has become more and more popular for mobile electronic applications. However, crack formation of the solder joint crack was occurred at low temperature curable acrylic polymer resins after bonding processes. In this study, the mechanism of SnBi58 solder joint crack at low temperature curable acrylic adhesive was investigated. In addition, SnBi58 solder joint cracks can be significantly removed by increasing the storage modulus of adhesives instead of coefficient of thermal expansion. The first approach of reducing the amount of polymer rebound can be achieved by using an ultrasonic bonding method to maintain a bonding pressure on the SnBi58 solder joints cooling to room temperature. The second approach is to increase storage modulus of adhesives by adding silica filler into acrylic polymer resins to prevent the solder joint from cracking. Finally, excellent acrylic based SnBi58 solder joints reliability were obtained after 1000 cycles thermal cycling test. Full article
(This article belongs to the Special Issue Science, Characterization and Technology of Joining and Welding)
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