Journal articles: 'Defect-free joints'

1

Leinenbach, Christian, Michael Koster, and Hans-Jakob Schindler. "Fatigue Assessment of Defect-Free and Defect-Containing Brazed Steel Joints." Journal of Materials Engineering and Performance 21, no. 5 (February 28, 2012): 739–47. http://dx.doi.org/10.1007/s11665-012-0182-7.

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Li, Weipo, Zhimin Liang, Congwei Cai, and Dianlong Wang. "Repair Welding of the Tunnel Defect in Friction Stir Weld." High Temperature Materials and Processes 37, no. 7 (July 26, 2018): 675–81. http://dx.doi.org/10.1515/htmp-2017-0026.

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AbstractThe tunnel defect formed in friction stir weld would dramatically push the mechanical properties of joints into deterioration. In this study, friction stir welding process was adopted to repair the joints of 7N01 aluminum alloy with tunnel defect. The effects of friction stir repair welding process on the microstructure and mechanical properties were comprehensively investigated. Microstructure of the repaired joints shows that the grain size in nugget zone decreases slightly while the recrystallization in the retreating side of thermo-mechanically affected zone is intensified as the joints are repaired. The microhardness of the repaired joints declined slightly compared with the defective joint. However, the yield strength and tensile strength increase and recover to the values of the joints free of defect. The longitudinal residual stress in weld zone increased remarkably as the repair times increase. Compared with the once repaired joint, yield strength and tensile strength of the twice repaired joint reduced slightly, and the throat thickness also reduced during the repeated repair welding process. Therefore, the times of repair welding applied should be limited actually.

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Barat, Vera, Artem Marchenkov, Vladimir Bardakov, Daria Zhgut, Marina Karpova, Timofey Balandin, and Sergey Elizarov. "Assessment of the Structural State of Dissimilar Welded Joints by the Acoustic Emission Method." Applied Sciences 12, no. 14 (July 18, 2022): 7213. http://dx.doi.org/10.3390/app12147213.

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In this study, we investigated defect detection in dissimilar welded joints by the acoustic emission (AE) method. The study objects were carbide and decarburized interlayers, which are formed at the fusion boundary between austenitic and pearlitic steels. Diffusion interlayers, as a structural defect, usually have microscopic dimensions and cannot be detected using conventional non-destructive testing (NDT) methods. In this regard, the AE method is a promising approach to diagnose metal objects with a complex structure and to detect microscopic defects. In this paper, the AE signatures obtained from testing defect-free specimens and specimens with diffusion interlayers are analyzed. We found that the AE signature for defective and defect-free welded joints has significant differences, which makes it possible to identify descriptors corresponding to the presence of diffusion interlayers in dissimilar welded joints.

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Motomura, Hisashi, Kensuke Nose, Masao Fujiwara, Toshiyuki Ozawa, Teruichi Harada, and Michinari Muraoka. "Arthroplasty of the Interphalangeal Joint of the Great Toe Using Costal Osteochondral Grafting." Journal of the American Podiatric Medical Association 96, no. 6 (November 1, 2006): 508–12. http://dx.doi.org/10.7547/0960508.

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Although many reports have been published on the usefulness of costal cartilage grafting in the reconstruction of interphalangeal joints of fingers, there are only a few published reports on the reconstruction of interphalangeal joints of toes. We describe a 21-year-old woman with a tissue defect of the dorsum pedis and a partial defect of the interphalangeal joint of the great toe caused by a motor-vehicle accident. We attempted arthroplasty using a free latissimus dorsi myocutaneous flap and a costal osteochondral graft. The grafted rib and cartilage survived, allowing the patient to resume functional ambulation for day-to-day activities. Arthroplasty using costal osteochondral grafts seems to be an effective means of reconstructing the interphalangeal joints of toes. (J Am Podiatr Med Assoc 96(6): 508–512, 2006)

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Al-jarrah, J. A., A. Ibrahim, and S. Sawlaha. "Effect of Applied Pressure on the Mechanical Properties of 6061 Aluminum Alloy Welded Joints Prepared by Friction Stir Welding." Engineering, Technology & Applied Science Research 7, no. 3 (June 12, 2017): 1619–22. http://dx.doi.org/10.48084/etasr.1124.

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This paper investigates the effect of axial force on the surface appearance and mechanical properties of 6061 aluminum alloy welded joints prepared by friction stir welding. The applied pressure varies from 1.44 to 10.07 MPa. The applied pressure was calculated from the axial force which exerted by a spring loaded cell designed for this purpose. Defect free joints obtained at an applied pressure of 3.62 MPa. The mechanical properties of the welded joints were evaluated through microhardness and tensile tests at room temperature. From this investigation, it was found that the joint produced with an applied pressure of 5.76 MPa exhibits superior tensile strength compared to other welded joints. The fracture of this joint happened at the base material.

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Yan, Yinfei, Yifu Shen, Keyu Shi, Jiaxin Wu, and Jinpeng Hu. "Friction plug repair welding of glass fiber-reinforced polyamide 6: Investigation of morphology, microstructure, and mechanical properties." Journal of Reinforced Plastics and Composites 39, no. 21-22 (June 15, 2020): 805–16. http://dx.doi.org/10.1177/0731684420932646.

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Friction plug repair welding technology has been demonstrated to be effective to repair the glass fiber-reinforced polyamide 6 sheets in the present paper. Influences of repair hole geometries and parameters on joint morphology and mechanical performance were investigated. Results showed that defect-free repaired joints were produced with the utilization of tapered holes rather than cylindrical holes. Process parameters exerted significant influences on the cross-sectional profile and morphology of the joints. Defect-free repaired welds with larger stir zone thicknesses were produced with the proper increase of rotational speeds, but excessive rotational speeds caused the formation of cavities along the plug boundary and the reduction of stir zone thicknesses. The fluctuation of the wavy bottom interface increased under larger plunge rates and incomplete connections between stir zone and base material were observed under plunge rate of 25 mm/min. Extended dwell time led to larger stir zone thickness and improved joint morphology. Tensile tests showed that the strength of the repaired joints increased and then decreased with the enlargement of rotational speeds. Decreased plunge rate and extended dwell time led to promoted joint mechanical performance. Three failure modes were observed, which corresponded to low, middle, and high repaired weld strengths.

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Wei, Yanni, Hui Li, Peng Xiao, and Juntao Zou. "Microstructure and Conductivity of the Al-Cu Joint Processed by Friction Stir Welding." Advances in Materials Science and Engineering 2020 (July 27, 2020): 1–10. http://dx.doi.org/10.1155/2020/6845468.

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In this paper, 1060 aluminum and T2 pure copper were joined by friction stir welding. The influence of the rotation speed and inclination on the microstructure and mechanical properties of the joint were investigated. The microstructure and composition of the welded interface region were analyzed. The joints’ strength was tested, and the conductivity of the joints was estimated. Joints having good surface formation and defect-free cross section were successfully obtained. The cross-sectional morphologies of the Al-Cu friction stir welding joints can be divided into three zones: the shoulder impact zone, the weld nugget zone, and the interface zone. The interface zone consisted of a metallurgical reaction layer and a visible mixed structure. The reaction layers were identified as Al2Cu, Al4Cu9 phases. The tensile strength of the joints reaches maximum values of 102 MPa at a rotation speed of 950 rpm and inclination of 0°, which was approximately equal to those of 1060Al base metal. The resistivity of the Al-Cu joint was approximately equal to the theoretical resistivity. The interfacial resistance is directly affected by the joint defects, compound types, and thickness of the intermetallic compound layer.

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Ivanov, Alexey, Valery Rubtsov, Andrey Chumaevskii, Kseniya Osipovich, Evgeny Kolubaev, Vladimir Bakshaev, and Ivan Ivashkin. "Features of structure formation processes in AA2024 alloy joints formed by the friction stir welding with bobbin tool." Metal Working and Material Science 23, no. 2 (June 10, 2021): 98–115. http://dx.doi.org/10.17212/1994-6309-2021-23.2-98-115.

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Introduction. One of friction stir welding types is the bobbin friction stir welding (BFSW) process, which allows to obtain welded joints in various configurations without using a substrate and axial embedding force, as well as to reduce heat loss and temperature gradient across the welded material thickness. This makes the BFSW process effective for welding aluminum alloys, which properties are determined by their structural-phase state. According to research data, the temperature and strain rate of the welded material have some value intervals in which strong defect-free joints are formed. At the same time, much less attention has been paid to the mechanisms of structure formation in the BFSW process. Therefore, to solve the problem of obtaining defect-free and strong welded joints by BFSW, an extended understanding of the basic mechanisms of structure formation in the welding process is required. The aim of this work is to research the mechanisms of structure formation in welded joint of AA2024 alloy obtained by bobbin tool friction stir welding with variation of the welding speed. Results and discussion. Weld formation conditions during BFSW process are determined by heat input into a welded material, its fragmentation and plastic flow around the welding tool, which depend on the ratio of tool rotation speed and tool travel speed. Mechanisms of joint formation are based on a combination of equally important processes of adhesive interaction in “tool-material” system and extrusion of metal into the region behind the welding tool. Combined with heat dissipation conditions and the configuration of the “tool-material” system, this leads to material extrusion from a welded joint and its decompaction. This results in formation of extended defects. Increasing in tool travel speed reduce the specific heat input, but in case of extended joints welding an amount of heat released in joint increases because of specific heat removal conditions. As a result, the conditions of adhesion interaction and extrusion processes change, which leads either to the growth of existing defects or to the formation of new ones. Taking into account the complexity of mechanisms of structure formation in joint obtained by BFSW, an obtaining of defect-free joints implies a necessary usage of various nondestructive testing methods in combination with an adaptive control of technological parameters directly in course of a welding process.

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Sevvel, P., and V. Jaiganesh. "Influence of The Arrangement of Materials and Microstructural Analysis During FSW of AZ80A & AZ91C Mg Alloys." Archives of Metallurgy and Materials 62, no. 3 (September 26, 2017): 1795–801. http://dx.doi.org/10.1515/amm-2017-0272.

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AbstractThe main objective of this paper is to produce defect free weldments with improved properties during friction stir welding of dissimilar Mg alloys. The influence of the anisotropic arrangement of materials when AZ80A Mg alloy is taken as advancing side and AZ91C Mg alloy as retreating side and vice versa with respect to their mechanical properties and microstructural characteristics were investigated. The effects of various FSW parameters on the quality of these joints were also analyzed and best optimized FSW parameters were suggested. Defect free sound joints with excellent mechanical properties were produced when AZ80A Mg alloy was positioned at retreating side. At the same time, it seems a little bit difficult to obtain good quality joints with the contrary arrangement of materials. These investigations revealed that materials having inferior plastic deformability must be kept at the advancing side to obtain sound joints during FSW of dissimilar alloys of Magnesium.

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Li, Tielong, and Zhenshan Wang. "Forming and Properties of Friction Stir Welding Process for Dissimilar Mg Alloy." Open Mechanical Engineering Journal 9, no. 1 (October 7, 2015): 859–64. http://dx.doi.org/10.2174/1874155x01509010859.

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For hot extrusions of magnesium alloy sheets, Dissimilar AZ80 and AZ31 were used, in which AZ80 was placed on advancing side and AZ31 on retreating side, using friction stir butt welding with different process parameters. Some defect-free welded joints with good weld surfaces could be obtained with some suitable welding conditions. The maximum tensile strength of welded joint which is 225.5 MPa can reach 98% that of the AZ31 base material. Influence of process parameters on defects, weld shaping and mechanical property were discussed systematically. And the microstructure of different zones was compared. The fracture of the welded joints takes place at the junction of mechanical heat affected zone and nugget zone in AZ31 magnesium alloy set retreating side, since existing difference in metallographic structure of alloy diversely suffered by heat, pressure and depositing impurities. Fracture initiation site may be the P line defect which should be eliminated, and the P line defect formation was analyzed.

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Lai, Huansheng, Dengshuai Fan, and Kanglin Liu. "The Effect of Welding Defects on the Long-Term Performance of HDPE Pipes." Polymers 14, no. 19 (September 21, 2022): 3936. http://dx.doi.org/10.3390/polym14193936.

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High-density polyethylene (HDPE) pipes are the preferred pipes of water systems in nuclear power plants because they are durable, corrosion-free, easy to install, and not subject to fouling. However, their long-term performance can be affected by welding defects. In this paper, the effect of welding defects on the long-term performance of HDPE pipe butt fusion joints was studied using a creep test. A welding defect with a hole or inclusion in the joint was simulated by artificially inserting a copper ball during butt fusion welding. The test results showed that the creep life of the joint decreased with increased defect size. An expression describing the creep life and the defect ratio was obtained according to the test results. In addition, the test results showed that the creep life of the joint without a welding bead was about 50% of that in a joint with a welding bead.

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Nath, Rahul Kanti, Vinayak Jha, Pabitra Maji, and John Deb Barma. "A novel double-side welding approach for friction stir welding of polypropylene plate." International Journal of Advanced Manufacturing Technology 113, no. 3-4 (January 12, 2021): 691–703. http://dx.doi.org/10.1007/s00170-021-06602-9.

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AbstractIn almost every industry, polymer materials are in high demand in recent years due to their lightweight and easy formability. However, eco-friendly, cost-efficient and defect-free joining of polymers is a major concern. In this article, a novel approach is taken for friction stir welding of polypropylene by implementing a double-side welding technique. The effect of tool rotational speed on construction and properties of the welded joints are studied. The torque and forces exerted on the tool during double-side welding are compared with single-side welding. Cross-sectional morphology examination using optical and scanning electron microscope reveals defect-free sound welding by double-side weld with uniform material flow. The molecular bonds of the welded specimens are examined by FTIR analysis. The double-side welding technique yields superior joints in terms of tensile strength and flexural strength than the joints obtained by single-side welding.

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Shashi Kumar, S., N. Murugan, and K. K. Ramachandran. "Effect of Cooling Rate on Mechanical and Microstructural Characterization of Friction Stir Welded 316 L Austenitic Stainless Steel Joints." Materials Science Forum 830-831 (September 2015): 314–18. http://dx.doi.org/10.4028/www.scientific.net/msf.830-831.314.

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The present investigation is carried out to investigate on mechanical and metallurgical properties of Friction stir (FS) / Underwater Friction stir (UFS) welded 3 mm thick AISI 316 L stainless steel joints. Experiments were carried out at a tool rotational speed of 700 rpm, welding speed of 45 mm/min and axial force of 12 kN. Defect free joints were confirmed by visual inspection. A marginal rise of about 4.5 % increase in the joint strength is achieved in water cooling than by gas cooling technique. Reduced peak temperature in water cooled joint led to better grain refinement in the weld nugget enhancing FSW tool life. No sign of secondary phase precipitation was observed in the weld joints which was confirmed by Energy Dispersive Spectroscopy (EDS) spectrums and micro etchants like Groesbeck and modified Murakami reagents in the weld nugget.

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14

Campanella, Davide, Harikrishna Rana, Toni Lupo, and Rosa Di Lorenzo. "A Comparative Study of Mechanical and Microstructural Behavior for Metal Active Gas and Friction Stir Welded Micro-Alloyed Structural Steel." Journal of Manufacturing and Materials Processing 6, no. 5 (September 16, 2022): 104. http://dx.doi.org/10.3390/jmmp6050104.

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Manufacturing tiny components into gigantic structures seems unimaginable without welding connections, whether it is for materials, parts, structures, or equipment. In the recent competitive market scenario, manufacturing industries are desperately looking for a viable alternative to fusion-based conventional material joining technologies, to improve upon cost-effectiveness along with performance. The present investigation is to evaluate the performance of structural steel thick plate joints prepared by advanced solid-state friction stir welding (FSW) over conventional metal active gas welding (MAG). The FSW experiments were carried out with different tool designs and configurations. The outcomes were evaluated in terms of microstructural integrity and mechanical joint resistance. Impressive results were obtained with FSW joints, characterized by an almost defect-free microstructure with a leaner heat-affected zone and higher joint resistance as compared to conventional MAG-welded joints.

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15

Shin, Won-Sang, Dae-Won Cho, Donghyuck Jung, Heeshin Kang, Jeng O. Kim, Yoon-Jun Kim, and Changkyoo Park. "Investigation on Laser Welding of Al Ribbon to Cu Sheet: Weldability, Microstructure, and Mechanical and Electrical Properties." Metals 11, no. 5 (May 19, 2021): 831. http://dx.doi.org/10.3390/met11050831.

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The pulsed laser welding of Al ribbon to Cu sheet was investigated for the electrical interconnections in power electronic modules. The various experimental conditions with the different laser powers, scan speeds, and heat inputs were employed for obtaining the defect-free Al/Cu joints. During the Al/Cu laser welding, the intermetallic compounds were formed in the welding zone. An electron probe microanalyzer and transmission electron microscopy confirmed the phases of intermetallic compounds, which were found to be Al4Cu9, Al2Cu, AlCu, etc. The computational fluid dynamics simulation revealed that the Marangoni effect induced the circulation of the molten pool, resulting in the mixture of Al and Cu and the formation of swirl-like structures at the Al/Cu joints. The tensile shear strengths and electrical resistances of the Al/Cu joints were measured, and they showed a strong correlation with the welding area. A decrease in mechanical strength and an increase in electrical resistance were measured with increasing the welding area of Al/Cu joints. Moreover, the process window for the defect-free Al/Cu joints was developed, and the experimental conditions for Al/Cu laser braze-welding were examined to minimize the intermetallic compounds formation at the Al/Cu joints.

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Ahmed, M. M. Z., A. Elnaml, M. Shazly, and M. M. El-Sayed Seleman. "The Effect of Top Surface Lubrication on the Friction Stir Welding of Polycarbonate Sheets." International Polymer Processing 36, no. 1 (March 1, 2021): 94–102. http://dx.doi.org/10.1515/ipp-2020-3991.

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Abstract In this work, top surface lubrication during friction stir welding of polycarbonate sheets was applied. A homogenous layer of Paraffin wax has been placed on the top surface of the joint area with a width that ensures to cover the shoulder diameter. Then FSW was applied using conventional FSW tool with rotating pin and shoulder at different FSW parameters (Rotation speeds of 1 000, 1500, 2 000 min–1 and welding speeds of 25, 50, 75,100 mm/min). The main objective of using the wax is to act as a lubricant that reduces the friction between the shoulder and the polycarbonate surface. The joints produced were investigated in terms of surface quality, internal defects, and mechanical properties. During FSW the wax is melted and played as lubricant between the tool shoulder and the polycarbonate surface and resulted in defect-free surface with no thickness reduction of the original plate. The transverse cross-section showed defect-free joints for the majority of the FSW parameters investigated. Tensile testing results showed a reduction of the tensile strength after FSW, and an enhancement in the tensile strength with the increase of welding speed or rotation speed. The fracture occurs at the joint zone and the fracture surface investigation using SEM showed the existence of spherulitic structure in the weld joint.

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Ramachandran, K. K., N. Murugan, and S. Shashi Kumar. "Study on Dissimilar Butt Joining of Aluminum Alloy, AA5052 and High Strength Low Alloy Steel through a Modified FSW Process." Materials Science Forum 830-831 (September 2015): 278–81. http://dx.doi.org/10.4028/www.scientific.net/msf.830-831.278.

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In the preset investigation, aluminum alloy, AA5052 and HSLA steel are successfully butt welded using a modified FSW process wherein the work pieces submerged in a liquid medium are stirred by the FSW tool. The trials are conducted by varying the tool rotational speed from 400 rpm to 900 rpm while keeping the other parameters constant. The welded joints are tested for ultimate tensile strength (UTS) and the joint interface microstructure is analyzed using SEM and EDS. The results show that when compared to the normal FSW process, the peak value of UTS is marginally low but the range of tool rotational speed that could produce defect free joints with good joint strength is almost doubled in the modified FSW process.

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Kim, Jong Woong, Hyun Suk Chun, Sang Su Ha, Jong Hyuck Chae, Jin Ho Joo, Young Eui Shin, and Seung Boo Jung. "Board-Level Reliability of Pb-Free Surface Mounted Assemblies during Thermal Shock Testing." Advanced Materials Research 15-17 (February 2006): 633–38. http://dx.doi.org/10.4028/www.scientific.net/amr.15-17.633.

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Board-level reliability of conventional Sn-37Pb and Pb-free Sn-3.0Ag-0.5Cu solder joints was evaluated using thermal shock testing. In the microstructural investigation of the solder joints, the formation of Cu6Sn5 intermetallic compound (IMC) layer was observed between both solders and Cu lead frame, but any crack or newly introduced defect cannot be found even after 2000 cycles of thermal shocks. Shear test of the multi layer ceramic capacitor (MLCC) joints were also conducted to investigate the effect of microstructural variations on the bonding strength of the solder joints. Shear forces of the both solder joints decreased with increasing thermal shock cycles. The reason to the decrease in shear force was discussed with fracture surfaces of the shear tested solder joints.

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Li, Bo, Yi Fu Shen, and Lei Yao. "The Influence of Cu/Ti Overlapping Region Microstructures on the Mechanical Tensile Properties of the Joint via Friction Stir Lap Welding." Advanced Materials Research 1142 (January 2017): 260–64. http://dx.doi.org/10.4028/www.scientific.net/amr.1142.260.

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The investigation on friction stir lap welding (FSLW) of dissimilar Cu and Ti is reported in this research, aiming to achieve a reliable solid-state joining and effectively control the intermetellic (IMC) formation at the lapping Cu/Ti dissimilar welded interfaces. Following the previous process optimization of the FSLW tool rotation speed and downward plunge value of the tool pin into the lower Ti sheet, the tool travel speed was further tailored for a defect-free joint. No significant Ti-Cu IMC was founded in the generated joints. After the analyses of tensile properties of the FSLW joints, the so-called mechanical locking effect of the Cu/Ti alternate band structure was further elucidated. The composite-like structure played a so-called mechanical locking effect on the Cu/Ti lap joints. The fracture resistant strength of the joint reached 95% of that of the used parent copper.

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Wang, Chao, Zhe Ming Zhu, and Tao Zheng. "The Fracturing Behavior of Detected Rock under Blasting Loads." Applied Mechanics and Materials 142 (November 2011): 193–96. http://dx.doi.org/10.4028/www.scientific.net/amm.142.193.

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In order to investigate the effect of defects on rock fracturing under dynamic loads, blasting experiments using PMMA specimens with pre-existing defects were conducted. The defects include holes, pores and small open joints, etc., and they are randomly distributed. In order to verify the experimental results, numerical simulation was implemented. It is shown that under blasting loads, most cracks initiate at pre-existing defect tips, and near free boundary, many cracks developed near defect tips are parallel the free boundary. The numerical results qualitatively agree with experimental results

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Xie, D. J., Y. C. Chan, J. K. L. Lai, and I. K. Hui. "Fatigue life studies on defect-free solder joints fabricated from modified reflow soldering." IEEE Transactions on Components, Packaging, and Manufacturing Technology: Part B 19, no. 3 (1996): 679–84. http://dx.doi.org/10.1109/96.533911.

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Chu, JianRu, Xiaosong Jiang, and Hongliang Sun. "Mechanical properties and microstructure evolution of C_f/SiC–Nb joints using Ti-base laminated foil." Materials Testing 64, no. 12 (November 29, 2022): 1818–25. http://dx.doi.org/10.1515/mt-2022-0229.

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Abstract A self-designed Ti–Zr–Cu composite foil was used as an interlayer and vacuum brazed to achieve a heterogeneous joint between the Cf/SiC composite and Nb, resulting in a well-bonded, defect-free joint with a typical interfacial microstructure of Cf/SiC/(Ti, Zr)C/(Ti, Zr)2Cu + Zr2Cu/Ti2Cu + (Ti, Nb)ss/Nb. The effects of different experimental temperatures on the microstructural evolution of the joints and the mechanical properties of the joints were investigated, and the formation mechanism of the joint interface was analyzed. The results show that the microscopic morphology and mechanical properties of the joint interface change significantly with increasing experimental temperature. As the temperature increased to 1080 °C, the shear strength increased by 150.6% compared to 1060 °C (78.09 MPa) and reached a maximum value of 195.72 MPa, but further warming to 1100 °C (144.25 MPa) resulted in a 26.3% decrease in shear strength, with the best joint achieved at 1080 °C.

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Okamoto, K., A. Sato, Seung Hwan C. Park, and Satoshi Hirano. "Microstructure and Mechanical Properties of FSWed Aluminum Extrusion with Bobbin Tools." Materials Science Forum 706-709 (January 2012): 990–95. http://dx.doi.org/10.4028/www.scientific.net/msf.706-709.990.

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Bobbin FSW technique is assessed in terms of process productivity and robustness considering the metallurgical and mechanical qualities of the joint. Several different designed bobbin tools were applied to aluminium A6xxx alloy extrusions, at feed rate of 400-1000mm/min with tool rotation speed of 600-1000rpm. In case of A6068-T6, a joint efficiency of 68% was achieved at 600mm/min, which is almost equivalent to the productivity and quality of the conventional FSWed joints, hence the potential of bobbin FSW technique was suggested. The bobbin tool design was further optimized considering the practical process robustness to the part fit issue, and defect free welds have been achieved for the joints with a set gap up to 1mm. However, the oxide remnant, so called “lazy S” was observed in a joint made with an inadequate designed tool, which significantly deteriorates the mechanical properties.

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Rajendran, Chinnasamy, Kasi Srinivasan, Visvalingam Balasubramanian, Haridasu Balaji, and Ponnumuthu Selvaraj. "Mechanical properties and microstructural characteristics of friction stir welded AA2014-T6 aluminium alloy joints." Journal of the Mechanical Behavior of Materials 28, no. 1 (December 31, 2019): 169–85. http://dx.doi.org/10.1515/jmbm-2019-0019.

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AbstractThe quality of friction stir welded joints depends upon the working parameters such as rotational speed, welding speed, shoulder diameter, tilt angle; etc. Each process parameter has a significant effect on the formation of joint strength. This investigation attempts to understand the effect of friction stir welding parameters on microstructural characteristics and tensile strength of AA2014-T6 aluminium alloy. This is performed by changing any one of the process parameters from minimum to maximum and keeping others constant. The joint fabricated from a rotational speed of 1500 rpm, welding speed of 40 mm/min, shoulder diameter of 6 mm and tilt angle of 1.5∘ yielded superior tensile properties compared to their counter joints. Due to the formation of defect-free weld, balanced material flow and uniform distribution of strengthening precipitates in the stir zone is achieved.

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Wong, Chak Kui, and Jonathan P. K. Doye. "The Free-Energy Landscape of a Mechanically Bistable DNA Origami." Applied Sciences 12, no. 12 (June 9, 2022): 5875. http://dx.doi.org/10.3390/app12125875.

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Molecular simulations using coarse-grained models allow the structure, dynamics and mechanics of DNA origamis to be comprehensively characterized. Here, we focus on the free-energy landscape of a jointed DNA origami that has been designed to exhibit two mechanically stable states and for which a bistable landscape has been inferred from ensembles of structures visualized by electron microscopy. Surprisingly, simulations using the oxDNA model predict that the defect-free origami has a single free-energy minimum. The expected second state is not stable because the hinge joints do not simply allow free angular motion but instead lead to increasing free-energetic penalties as the joint angles relevant to the second state are approached. This raises interesting questions about the cause of this difference between simulations and experiment, such as how assembly defects might affect the ensemble of structures observed experimentally.

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Padmanaban, R., V. Muthukumaran, and A. Vighnesh. "Parameter Optimization for Friction Stir Welding AA1100." Applied Mechanics and Materials 813-814 (November 2015): 462–66. http://dx.doi.org/10.4028/www.scientific.net/amm.813-814.462.

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Friction stir welding (FSW) has become a potential solid state joining technique with considerable advantages over conventional joining process. Defect-free friction stir welded joints with high joint strength are obtained when optimum process parameters are used. Although a large number of parameters govern the FSW process, the tool rotation speed, Welding speed and tool geometry are key parameters that influence the joint strength. In this work, a statistical model relating process parameters and the tensile strength (TS) of friction stir welded AA1100 joints is build using response surface methodology. The four independent variables are tool rotational speed (TRS), welding speed (WS), shoulder diameter (SD) and pin diameter (PD). Central Composite design is used and Analysis of Variance at 95% confidence level was applied to assess the adequacy of the developed model. Genetic algorithm is used for optimizing the parameters. The optimum process parameter values predicted using the genetic algorithm are as follows. Tool rotation speed: 1001.9 rpm; welding speed: 62 mm/min; shoulder diameter: 17.8 mm and pin diameter: 6.5 mm. The corresponding tensile strength of the joints is 73.1556 MPa

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Wang, Wenyang, Ye Hu, Tong Wu, Dan Zhao, and Hongwei Zhao. "Effect of Rotation Speed on Microstructure and Mechanical Properties of Friction-Stir-Welded 2205 Duplex Stainless Steel." Advances in Materials Science and Engineering 2020 (May 5, 2020): 1–13. http://dx.doi.org/10.1155/2020/5176536.

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In the present study, 1.86-mm-thick steel plates (UNS S32205) were friction-stir-welded at various rotation speeds of 300 to 600 rpm and a constant welding speed of 100 mm·min−1. The effect of rotation speed on the microstructure and mechanical properties of the welds was researched. The welding temperature was recorded during friction stir welding (FSW), and the microstructure and mechanical properties of the welds were assessed. The incomplete penetration defect was formed at 300 rpm due to the insufficient heat input, and macroscopic groove-like defect was formed at 600 rpm because of the serious sticking of tool. Defect-free welds were obtained at 350 to 500 rpm. The lower rotation speed corresponds to lower heat input during FSW, which resulted in finer recrystallized grains within the stirred zone and thermomechanically affected zone. The joint width was increased with the increasing rotation speed. Therefore, both the strength and hardness of the weld joints increased with the decreasing of rotation speed.

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Venkateswaran, T., T. Thinesh Babu, M. Agilan, D. Sivakumar, Bhanu Pant, and D. P. Sudhakar. "Effect of Varying Process Parameters on the Microstructure and Mechanical Properties of Cu-Cr-Zr-Ti Alloy Brazed Using Cu-Mn-Ni-Sn-Fe Foil." Materials Science Forum 830-831 (September 2015): 253–56. http://dx.doi.org/10.4028/www.scientific.net/msf.830-831.253.

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Cu-Cr-Zr-Ti alloy is being used widely in aerospace engines, due to its synergetic combination of high strength and thermal conductivity. Brazing is the preferred process being adopted to realize intricate shapes and complex dimensions. In the present work, Cu-Cr-Zr-Ti alloy was brazed using Cu-Mn-Ni-Sn-Fe base brazing foil. This braze foil exhibits liquidus temperature of ~980°C. Brazing experiments were carried out at 1030°C under high vacuum condition. The effect of varying load (0.5-2 kg) has been studied in the current experiment. Microstructural study of the parent materials and joints were carried out using optical microscope (OM). Lap shear testing (1T configuration) of the brazed joints was evaluated to obtain shear strength values. Also, micro-hardness traverse has been carried out across the brazed joint. Applied load plays a significant role in obtaining defect free braze joint.

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Sabry, Dina, Ashraf Shamaa, Mohamed Amer, Omar El-Tookhy, Ahmed Abdallah, Dalia Mohamed Abd El Hassib, Eman Amer, and Azza Elamir. "THE EFFECT OF MESENCHYMAL STEM CELL DERIVED MICROVESICLES IN REPAIR OF FEMORAL CHONDRAL DEFECTS IN DOGS." Journal of Musculoskeletal Research 21, no. 02 (June 2018): 1850006. http://dx.doi.org/10.1142/s0218957718500069.

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Mesenchymal stem cells (MSCs) releases in culture extracellular vesicles called microvesicles (MVs). MVs have beneficial cytokines that prevent progression of the disease and help in the regeneration process. This study is aimed to evaluate the effect of MSCs derived MVs in repair of induced chondral defect in a dog model. Methods: Chondral defects were created surgically ([Formula: see text][Formula: see text]mm) in both femoral condyles of nine dogs, autologous MSCs were isolated and MVs were prepared and injected intraarticularly in the right joint. The left joint was injected with normal saline as control negative. Evaluation of the treatment after first injection was carried out by physical examination and histopathology at different time periods ([Formula: see text]½, 3 and 6 months). Results: Treated joints showed marked degree of cartilage regeneration and restoration of chondral histomorphological picture on the contrary of the control joints that showed deterioration over time and defect filling with only fibrous tissue forming a fibrocartilage at the end of six months period. Conclusion: We demonstrated in this study that administration of MVs was effective on the functional and morphological recovery of the injured cartilage and could be exploited as a cell free therapeutic approach in regenerative medicine.

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Liu, Dong Ming, Bin Han, and Li Ying Li. "Microstructure and Mechanical Properties of the Weld Joint of Small Diameter Glass-Lined Metal Pipe with Inner Surface Layer." Materials Science Forum 850 (March 2016): 1004–9. http://dx.doi.org/10.4028/www.scientific.net/msf.850.1004.

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The width of 36mm of inner surface layer was formed by Ni625 welding wires in the ends of glass-lined 20# metal pipe, and the metal tubes were welded. The microstructure and the distribution of the main alloying elements of the weld joints were analyzed by optical microscope (OM) and electron probe microscope analysis (EPMA). The mechanical property and nondestructive inspection tests of the welded joints were carried out. The results show that the welded joints were divided into three layers including root layer, transition layer and cap layer. The microstructure in root layer was characterized by the cellular-dendrite structure. The transition layer contained martensite and retained austenite. The capping layer included acicular ferrite and pearlite. The defect free joint was produced and performed well. The concentration of nickel and chromium element in weld root were higher than inner surface layer which proves that welding wire of transition layer protects the major alloying elements in welding root.

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Saleh, Mohamed I., Hans J. Roven, Tahir I. Khan, and Terje Iveland. "Transient Liquid Phase Bonding of Al-6063 to Steel Alloy UNS S32304." Journal of Manufacturing and Materials Processing 2, no. 3 (September 1, 2018): 58. http://dx.doi.org/10.3390/jmmp2030058.

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Transient liquid phase (TLP) bonding of 6063 aluminum alloy (Al-6063) and duplex alloy 2304 stainless steel (UNS S32304) was performed using copper foil as an interlayer between the base metals. A compression load was applied normal to the specimens. Metallurgical examination of the produced joints showed three distinct regions including a reaction zone, diffusion affected zone, and the base metals. The diffusion of copper into aluminum resulted in an Al–Cu eutectic structure. However, the oxide layer on the aluminum surface controlled the dissolution behavior of copper and the extent of its wettability with the base metals. Although voids and intermetallic compounds were detected at the interfaces of the processed joints, a defect free joint was produced at 570 °C. In addition, the results from corrosion tests showed that the use of copper as an interlayer decreased the corrosion resistance of the joints. However, increase in thickness of the joining reaction zone with increasing bonding temperature was observed to increase corrosion resistance.

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He, Di Qiu, Rui Lin Lai, Shao Hua Xu, Kun Yu Yang, Shao Yong Ye, Jian Wang, Jian Ming Zhu, and Bin Su. "Microstructure and Mechanical Properties of Cu-Cr-Zr Alloy by Friction Stir Welding." Advanced Materials Research 602-604 (December 2012): 608–11. http://dx.doi.org/10.4028/www.scientific.net/amr.602-604.608.

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In this study, Cu-Cr-Zr alloy joints are successfully fabricated by friction stir welding (FSW). Defect-free weld are produced on 12mm thick Cu-Cr-Zr alloy plate useing a non-consumable tool with a specially designed and shoulder with a constant rotation speed and a fixed traverse speed. The effect of friction stir welding (FSW) on the microstructure and mechanical properties of Cu-Cr-Zr alloy joints are investigated in details: The joints showed the presence of various zones such as nugget zone (NZ) and thermo-mechanically affected zone (TMAZ) and base metal (BM), the microhardness and the tensile strength of welded joints are lower than that of the base material.

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33

Jaiganesh, V., P. K. Nagarajan, P. Sevvel, J. Dhileep Kumar, and S. Manivannan. "Impact of Tool Pin Geometry and Optimized Process Parameters on Mechanical Properties of Friction Stir Welded AZ80A Mg Alloy." Materials Science Forum 866 (August 2016): 151–55. http://dx.doi.org/10.4028/www.scientific.net/msf.866.151.

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In this paper, the influence of optimized FSW process parameters namely tool rotational speed, feed rate, mechanical axial force and impact of tool pin geometry on the mechanical properties of AZ80A Mg alloy are experimentally investigated in a detailed manner. M35 grade High Speed Steel (HSS) tool with three different pin geometries namely straight cylindrical, threaded cylindrical and taper cylindrical was employed in this investigation. The joints obtained under these conditions are subjected to tensile tests as per ASTM (American Society for Testing and Materials) B557M – 10 standards and tensile fracture surfaces are examined using optical and Scanning Electron Microscope (SEM). The investigations proved that defect free sound joints with better mechanical properties are produced by taper cylindrical tool pin geometry under optimized process parameter values. It was experimentally found that the optimized FSW process parameter values namely 1.0 mm/min feed rate, 5 kN axial force, 1000 rpm of tool rotational speed along with a taper cylindrical pin profiled tool is preferable for FSW of AZ80A Mg alloy of 5mm thickness.Moreover, this experimental work revealed us that the taper cylindrical pin profiled tool fabricated sound, defect free welded joints along with better & improved mechanical properties when compared with other two pin profiles.

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Joshi, Gaurang R., Vishvesh J. Badheka, Raghavendra S. Darji, Ankit D. Oza, Vivek J. Pathak, Dumitru Doru Burduhos-Nergis, Diana Petronela Burduhos-Nergis, Gautam Narwade, and Gopinath Thirunavukarasu. "The Joining of Copper to Stainless Steel by Solid-State Welding Processes: A Review." Materials 15, no. 20 (October 17, 2022): 7234. http://dx.doi.org/10.3390/ma15207234.

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Joining immiscible materials such as copper and stainless steel together is a significant concern due to distinct mechanical and metallurgical properties across the joint line, such as melting points, the coefficient of linear thermal expansion, and thermal conductivity. The joint properties of copper to stainless steel welds are in great demand for various mechanical components of the international thermonuclear experimental reactor, ultra-high vacuum system, plan wave linear-accelerator or linac structure, and heat exchanger. These dissimilar-metals joints offer excellent flexibility in design and production, leading to a robust structure for many cutting-edge applications. Hence, the present article reviews the copper to stainless steel joining mechanism under different solid-state processing conditions. The present understanding says that defect-free strong joints between the dissimilar metals are systematically possible. Apart from this understanding, the authors have identified and highlighted the gaps in the research exploration to date. Moreover, a sustainable methodology to achieve a desirable weld of copper to stainless steel depends on favorable processing conditions.

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Rafikov, S. K., A. P. Vatolin, G. S. Sharnina, and K. V. Kozhaeva. "Analysis of Reliability of Welded Connections Liquefied Gas and Condensate Pipelines." IOP Conference Series: Earth and Environmental Science 988, no. 2 (February 1, 2022): 022053. http://dx.doi.org/10.1088/1755-1315/988/2/022053.

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Abstract To assess the strength and reliability of welded joints, the metal of welded joints of the unstable condensate pipeline was tested for static tension and low-cycle durability. The tests were carried out on defect-free specimens, specimens with defects such as lack of fusion, undercut, single pore, single slag inclusion and specimens with defects combining lack of fusion and undercut. A comparative analysis of the effect of defects combining lack of penetration and undercut and separately located defects such as lack of penetration, undercut, single pore, single slag inclusion on tensile strength and low-cycle durability of welded joints is carried out.

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Azevedo, José, Virgínia Infante, Luisa Quintino, and Jorge dos Santos. "Fatigue Behaviour of Friction Stir Welded Steel Joints." Advanced Materials Research 891-892 (March 2014): 1488–93. http://dx.doi.org/10.4028/www.scientific.net/amr.891-892.1488.

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The development and application of friction stir welding (FSW) technology in steel structures in the shipbuilding industry provide an effective tool of achieving superior joint integrity especially where reliability and damage tolerance are of major concerns. Since the shipbuilding components are inevitably subjected to dynamic or cyclic stresses in services, the fatigue properties of the friction stir welded joints must be properly evaluated to ensure the safety and longevity. This research intends to fulfill a clear knowledge gap that exists nowadays and, as such, it is dedicated to the study of welded steel shipbuilding joints in GL-A36 steel, with 4 mm thick. The fatigue resistance of base material and four plates in as-welded condition (using several different parameters, tools and pre-welding conditions) were investigated. The joints culminate globally with defect-free welds, from which tensile, microhardness, and fatigue analyses were performed. The fatigue tests were carried out with a constant amplitude loading, a stress ratio of R=0.1 and frequency between 100 and 120 Hz. The experimental results show the quality of the welding process applied to steel GL-A36 which is reflected in the mechanical properties of joints tested.

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Xiao, B. L., Dong Wang, J. Bi, Z. Zhang, and Z. Y. Ma. "Friction Stir Welding of SiCp/Al Composite and 2024 Al Alloy." Materials Science Forum 638-642 (January 2010): 1500–1505. http://dx.doi.org/10.4028/www.scientific.net/msf.638-642.1500.

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6 mm thick SiCp/2009Al composite and 2024Al-T351 alloy plates were successfully joined by friction stir welding (FSW) with and without the tool pin offsetting to the 2024Al side (denoted as NOS and OS samples, respectively), producing defect-free joints. The SiC particles from the composite were distributed along a ring structure in the nugget and the volume fraction of the SiC particles decreased as the tool pin offset to the 2024Al side. The Al-clad layer on the 2024Al plate was aggregated on the retreating side of the nugget after FSW. For the OS sample, the Al formed a layer along the nugget boundary. The strength of the NOS sample reached up to 85% of the 2024Al alloy with the joint failing in the heat affected zone on the 2024Al side. The strength of the OS samples was 47% of the 2024Al alloy due to the aggregated Al layer on the retreating side of the nugget which decreased the strength of the joint.

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Rajarajan, Chakkaravarthi, Paramasivam Sivaraj, Tushar Sonar, Selvaraj Raja, and Nallusamy Mathiazhagan. "Nugget formation, microstructural features and strength of resistance spot welded cold-rolled dual-phase steel lap joints for automotive applications." Materials Testing 64, no. 8 (August 1, 2022): 1223–33. http://dx.doi.org/10.1515/mt-2021-2195.

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Abstract The main objective of this research paper is to investigate the nugget formation, microstructure and strength performance of DP 800 steel joints developed using resistance spot welding (RSW) process for automotive application. The influence of RSW parameters on nugget formation was studied using one variable at a time approach. The RSW joint showing optimum nugget area was further characterized for microstructural features and strength performance. The microstructural features of nugget were studied using optical and scanning electron microscopy (SEM). The lap tensile shear fractured specimens were analyzed using SEM for optimized condition. The microstructural features were correlated to the tensile shear strength and hardness of RSW joints. Results showed that welding current significantly influences the nugget formation than electrode force and welding time. The DP 800 RSW joints made using a welding current of 5.5 kA, an electrode pressure of 4.0 MPa and a welding time of 2.0 s disclosed defect free weld nugget of 7.28 mm diameter. It showed a higher tensile shear strength of 20 kN and microhardness of 564 HV thereby satisfying the requirement of automotive applications.

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Singh, Avanendra, Kartik Senapati, Biswarup Satpati, and Pratap K. Sahoo. "Suppression of near band edge emission in specially engineered ZnO twin nanorods." Physical Chemistry Chemical Physics 19, no. 21 (2017): 14012–19. http://dx.doi.org/10.1039/c7cp01880k.

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Twin crystalline ZnO nanorods with tunable amorphous joints are synthesized via a hydrothermal route. We find a strong coupling of acoustic phonon modes to free excitons in these structures. As a result, significant non-radiative transfer of carriers from the conduction band to defect bands occurs, leading to a loss of the near band edge emission intensity below ∼180 K.

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Muhayat, Nurul, Triyono, Bambang Kusharjanta, and Radian T. Handika. "Effect of Preheat Temperature on Friction Stir Welded Aluminum Alloy 5052 Joints." Applied Mechanics and Materials 597 (July 2014): 253–56. http://dx.doi.org/10.4028/www.scientific.net/amm.597.253.

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The effects of preheat temperature on mechanical properties and the microstructure of friction stir welded (FSW) aluminum alloy 5052 joints were studied in the present work. Heated air from Hot Gun was applied in front of the FSW tool to give the preheat on friction stir welding process. Preheat temperature was set 150°C, 250°C and 300°C. Mechanical properties were correlated and analyzed according to tensile strength, macro and microstructure. Defect free weldswere obtained at all preheat variations. The increasing preheat temperature produced the coarser grain size, it influencedthe little decrease both the tensile strength and hardness of joints.

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41

Gao, Shikang, Li Zhou, Guangda Sun, Huihui Zhao, Xiaolong Chu, Gaohui Li, and Hongyun Zhao. "Influence of Welding Speed on Microstructure and Mechanical Properties of 5251 Aluminum Alloy Joints Fabricated by Self-Reacting Friction Stir Welding." Materials 14, no. 20 (October 18, 2021): 6178. http://dx.doi.org/10.3390/ma14206178.

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In the present study, 8 mm-thick 5251 aluminum alloy was self-reacting friction stir welded (SRFSW) employing an optimized friction stir tool to analyze the effect of welding speed from 150 to 450 mm/min on the microstructure and mechanical properties at a constant rotation speed of 400 rpm. The results indicated that high-quality surface finish and defect-free joints were successfully obtained under suitable process parameters. The microhardness distribution profiles on the transverse section of joint exhibited a typical “W” pattern. The lowest hardness values located at the heat-affected zone (HAZ) and the width of the softened region decreased with increasing welding speed. The tensile strength significantly decreased due to the void defect, which showed mixed fracture characteristics induced by the decreasing welding speed. The average tensile strength and elongation achieved by the SRFSW process were 242.61 MPa and 8.3% with optimal welding conditions, and the fracture surface exhibited a typical toughness fracture mode.

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42

Wakchaure, Kiran, Rakesh Chaudhari, Ajaykumar Thakur, Kishan Fuse, Luis Norberto Lopez de Lacalle, and Jay Vora. "The Effect of Cooling Temperature on Microstructure and Mechanical Properties of Al 6061-T6 Aluminum Alloy during Submerged Friction Stir Welding." Metals 13, no. 7 (June 22, 2023): 1159. http://dx.doi.org/10.3390/met13071159.

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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).

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Zheng, Xiao Mao, and Da Tong Zhang. "Effect of Post-Welded Heat Treatments on Microstructure and Mechanical Properties of Friction Stir Welded Joints of 7A04-O Aluminum Alloy." Materials Science Forum 817 (April 2015): 212–18. http://dx.doi.org/10.4028/www.scientific.net/msf.817.212.

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Effect of post-welded heat treatment (PWHT) on the microstructure and mechanical properties of friction stir welded 7A04-O aluminum alloy was investigated. Solution heat treatment (ST) and artificial aging (T6) were given to specimens to improve the mechanical properties of the joints. The results show that defect-free joint was obtained via FSW and the microstructure of nugget zone was characterized by fine and equiaxed grains. After ST, most second phases dissolve in the matrix and the α-Al grains became coarse. Second phases precipitated in the α-Al matrix uniformly after T6 treatment. The Vickers hardness test shows that PWHT made the hardness distribution of the joints more evenly. The tensile test results indicate that the tensile strength of the joint increased from 228 MPa (in as-welded condition) to 440 MPa and 528 MPa after ST and T6 treatment respectively, but the elongation decreased to a certain extent. SEM fracture morphologies indicate that the joint failed through ductile fracture for the as-welded and ST states, and failed in a mixture mode of brittle fracture and ductile fracture for the T6 state.

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Zubaydi, Achmad, Nurul Muhayat, Sulistijono, M. Zaed Yuliadi, Budie Santosa, Dony Setyawan, and Syaiful Haqi. "Effect of Backplate Thermal Diffusivity on Mechanical Properties of Double Sided Friction Stir Welded Aluminum for Ship Structure." Applied Mechanics and Materials 597 (July 2014): 219–22. http://dx.doi.org/10.4028/www.scientific.net/amm.597.219.

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The effects of backplate thermal diffusivity on mechanical properties of friction stir welded (FSW) aluminum alloy 5083 joints were studied in the present work. Three variation of backplate material, marble-block, mild steel and aluminum which represent low, medium and high diffusivity respectively, were used in the welding processes. The results showed that the increase of backplate thermal diffusivity resulted the decrease of the welding temperature. Defect free weld was obtained if backplate material was mild steel, whereas the other backplate material, marble-block and aluminum were obtained defect welds. The highest tensile strength as well as microhardness were obtained in the mild steel backplate.

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Thomas, Joby V., K. Thomas Tharian, C. R. Anoop, and P. Chakravarthy. "Influence of Filler Wire Material on Dissimilar Welding of 15-5PH to KC20WN (Haynes 25)." Materials Science Forum 830-831 (September 2015): 298–301. http://dx.doi.org/10.4028/www.scientific.net/msf.830-831.298.

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Many of the components/assemblies used in strategic sectors involve dissimilar metal weld joints and dissimilar welding has always imposed challenges in terms of the weld quality because of the physical and chemical mismatches of the base metals. In the present study, dissimilar welding of stainless steel 15-5PH (UNS S15500) to a Cobalt-base super alloy KC20WN (UNS R30605/ Haynes 25) is attempted for specific purpose in space applications. Gas Tungsten Arc Welding is carried out with two types of filler wires, viz., KC20WN and ER 630 (17-4PH). Visual inspection, Dye Penetrant testing and X-ray radiography testing revealed defect free joints and the joints were also characterized for microstructure. Superior properties were observed when welding was carried out with KC20WN filler wire compared to that with ER630 filler wire.

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Ahmed, Mohamed M. Z., Mohamed I. A. Habba, Mohamed M. El-Sayed Seleman, Khalil Hajlaoui, Sabbah Ataya, Fahamsyah H. Latief, and Ahmed E. EL-Nikhaily. "Bobbin Tool Friction Stir Welding of Aluminum Thick Lap Joints: Effect of Process Parameters on Temperature Distribution and Joints’ Properties." Materials 14, no. 16 (August 15, 2021): 4585. http://dx.doi.org/10.3390/ma14164585.

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Bobbin tool friction stir welding (BT-FSW) is characterized by a fully penetrated pin and double-sided shoulder that promote symmetrical solid-state joints. However, control of the processing parameters to obtain defect-free thick lap joints is still difficult and needs more effort. In this study, the BT-FSW process was used to produce 10 mm AA1050-H14 similar lap joints. A newly designed bobbin tool (BT) with three different pin geometries (cylindrical, square, and triangular) and concave shoulders profile was designed, manufactured, and applied to produce the Al alloy lap joints. The experiments were carried out at a constant tool rotation speed of 600 rpm and a wide range of various welding travel speeds of 200, 400, 600, 800, and 1000 mm/min. The generated temperature during the BT-FSW process was recorded and analyzed at the joints’ center line, and at both advancing and retreating sides. Visual inspection, macrostructures, hardness, and tensile properties were investigated. The fracture surfaces after tensile testing were also examined. The results showed that the pin geometry and travel speed are considered the most important controlling parameters in BT-FSW thick lap joints. The square (Sq) pin geometry gives the highest BT-FSW stir zone temperature compared to the other two pins, cylindrical (Cy) and triangular (Tr), whereas the Tr pin gives the lowest stir zone temperature at all applied travel speeds from 200 to 1000 mm/min. Furthermore, the temperature along the lap joints decreased with increasing the welding speed, and the maximum temperature of 380 °C was obtained at the lowest travel speed of 200 mm/min with applying Sq pin geometry. The temperature at the advancing side (AS) was higher than that at the retreating side (RS) by around 20 °C. Defect-free welds were produced using a bobbin tool with Cy and Sq pin geometries at all the travel welding speeds investigated. BT-FSW at a travel speed of 200 mm/min leads to the highest tensile shear properties, in the case of using the Sq pin. The hardness profiles showed a significant effect for both the tool pin geometry and the welding speed, whereas the width of the softened region is reduced dramatically with increasing the welding speed and using the triangular pin.

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47

Mortensen, Adam W., and Roger M. Devaney. "Characterization of Black Pad Defect on Electroless Nickel- Immersion Gold (ENIG) Plated Circuits." International Symposium on Microelectronics 2010, no. 1 (January 1, 2010): 000608–14. http://dx.doi.org/10.4071/isom-2010-wp3-paper1.

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The advent of the RoHS legislation, which mandated lead-free solders, and the rise in popularity of the BGA package, have resulted in ENIG becoming a popular choice for surface finish due to its excellent long term solderability and surface planarity. One of the pitfalls of this surface finish is the possibility of creating a layer of overly elevated phosphorous content between the electroless nickel and immersion gold, known as black pad defect. Most of the available literature suggests black pad defect is caused by accelerated reduction (corrosion) of the nickel in the nickel- phosphorus (Ni-P) layer during the immersion gold step of the ENIG process. Black pad defect can manifest as corrosion spikes at the nodule boundaries in the Ni-P and can progress to an abnormally thick high phosphorus region at the top of the Ni-P. One failure mechanism associated with black pad defect is the brittle failure of well wetted solder joints from the underlying Ni-P layer due to the presence of the high phosphorus region. In severe cases, black pad defect can cause solderability issues and retard the formation of tin-nickel intermetallic preventing good wetting of the solder joint. We have had the opportunity to examine many different cases of black pad, from severe to mild, and have a large amount of knowledge to share. This paper will give the reader a basic understanding of how to recognize black pad and subsequently determine its severity.

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Kosturek, Robert, Janusz Torzewski, Marcin Wachowski, and Lucjan Śnieżek. "Effect of Welding Parameters on Mechanical Properties and Microstructure of Friction Stir Welded AA7075-T651 Aluminum Alloy Butt Joints." Materials 15, no. 17 (August 28, 2022): 5950. http://dx.doi.org/10.3390/ma15175950.

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The aim of this study was to examine the mechanical properties of 5-mm-thick AA7075-T651 alloy using three different welding velocities, 50, 75 and 100 mm/min, and four various sets of tool rotation speeds: 400, 600, 800 and 1000 rpm. All obtained joints were defect-free. In all cases, the values of UTS exceeded 400 MPa, corresponding to 68.5% minimum joint efficiency. The highest value of 447.7 MPa (76.7% joint efficiency) was reported for the joint produced via 400 rpm tool rotation speed and 100 mm/min welding velocity. The SZ microstructure of the strongest joint was characterized by a 5.2 ± 1.7 μm grain size and microhardness of approximately 145 HV0.1. The TMAZ/HAZ interface was identified as the low-hardness zone (105–115 HV0.1, depending on parameters), where the failure of the tensile samples takes place. The fracture mechanism is dominated by a transgranular ductile rupture with microvoid coalescence.

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Gusarova, Anastasia, Valery Rubtsov, Evgeny Kolubaev, Vladimir Bakshaev, and Yury Nikitin. "The Influence of the Rolling Direction of AA5056 on the Microstructure and Properties of Weld Joints obtained by Friction Stir Welding." Metal Working and Material Science 22, no. 4 (December 8, 2020): 124–36. http://dx.doi.org/10.17212/1994-6309-2020-22.4-124-136.

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Introduction. Heat emission and plastic deformation during friction stir welding (FSW) cause profound changes in the microstructure and structural properties of weld joints. The grain size, crystallographic texture evolution and second-phase precipitate are the most important microstructural changes during welding of aluminum alloys, which largely influence the strength properties of weld joints. In addition to process-dependent parameters (instrument sump force, its rotation frequency, and travel rate) of the FSW process, a significant factor, determining the properties of the obtained weld joints, is also a mutual orientation of structural elements of the weld material and the direction of the instruments impact on the material during welding. In this regard, the purpose of the work is to analyze the combined influence of the direction of the initial rolling and the instrument pressure during FSW on the structure and properties of weld joints from the AA5056 aluminum alloy. Methods. Research methods are mechanical tests for statistical tension, microhardness as well as metallographic analysis of the structure of welded joints. Results and discussion. As a result, it is established that at low values of the axial force on the instrument (7 kN), defects such as the joint line and voids are observed in welded joints both rolling and transverse directions. When the load increases from 8 kN to 12 kN, defect-free weld joints with enhanced mechanical properties form. It is determined that the rolling direction of AA5056 during FSW does not influence the structure and tensile strength of the weld joints, but it influences the relative elongation and microhardness. It is shown that in the stir zone of the weld joint, obtained by FSW in the transverse direction of AA5056 flats, the relative elongation is 1.3-2 times greater, and the microhardness is by 4-10% greater than that in the stir zone of weld joints, obtained by FSW in the rolling direction of AA5056 flats.

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Ceschini, Lorella, Alessandro Morri, Fabio Rotundo, Tea Sung Jun, and Alexander M. Korsunsky. "A Study on Similar and Dissimilar Linear Friction Welds of 2024 Al Alloy and 2124Al/SiC_P Composite." Advanced Materials Research 89-91 (January 2010): 461–66. http://dx.doi.org/10.4028/www.scientific.net/amr.89-91.461.

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Abstract:

The aim of the present work is to evaluate the possibility of using the Linear Friction Welding (LFW) technique to produce similar and dissimilar joints between a 2024 Al alloy and a 2124Al/25vol.%SiCP composite. In this solid state joining process the bonding of two flat edged components is achieved through frictional heating induced by their relative reciprocating motion, under an axial compressive force. Microstructural characterization of the welds was carried out by optical and scanning electron microscopy, to investigate the effect of LFW both on the aluminium alloy matrix and the reinforcement particles. The mechanical behaviour of the welded specimens was studied by means of hardness and tensile tests. The mechanisms of failure were investigated by SEM analyses of the fracture surfaces. LFW joints in MMCs resulted substantially defect free, with a uniform particle distribution, while a partial lack of bonding at the corners was observed in the others welds. The hardness decreased by approximately 10% in the welded zone, with some data fluctuations due to the complex microstructural modifications introduced by the LFW process. The joint efficiency, evaluated in respect to the UTS, was 90% for the Al alloy joints and 80% for the MMC joints. A decrease in the elongation to failure was measured in all the LFW specimens, probably related to the orientation of the plastic flow in the TMAZ, where the fracture generally occurred.

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