scholarly journals Investigation of Interfacial Layer for Friction Stir Scribe Welded Aluminum to Steel Joints

2018 ◽  
Vol 140 (11) ◽  
Author(s):  
Kaifeng Wang ◽  
Piyush Upadhyay ◽  
Yuxiang Wang ◽  
Jingjing Li ◽  
Xin Sun ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Driving Force ◽  
Bond Formation ◽  
Welding Process ◽  
High Strength ◽  
Bimaterial Interface ◽  
Joint Interface ◽  
Friction Stir ◽  
Transmission Electron ◽  
Steel Joints

Friction stir scribe (FSS) welding as a recent derivative of friction stir welding (FSW) has been successfully used to fabricate a linear joint between automotive Al and steel sheets. It has been established that FSS welding generates a hook-like structure at the bimaterial interface. Beyond the hook-like structure, there is a lack of fundamental understanding on the bond formation mechanism during this newly developed FSS welding process. In this paper, the microstructures and phases at the joint interface of FSS welded Al to ultra-high-strength steel were studied using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). It was found that both mechanical interlocking and interfacial bonding occurred simultaneously during the FSS welding process. Based on SEM observations, a higher diffusion driving force in the advancing side was found compared to the retreating side and the scribe swept zone, and thermally activated diffusion was the primary driving force for the interfacial bond formation in the scribe swept region. The TEM energy-dispersive X-ray spectroscopy (EDXS) revealed that a thin intermetallic compound (IMC) layer was formed through the interface, where the thickness of this layer gradually decreased from the advancing side to the retreating side owing to different material plastic deformation and heat generations. In addition, the diffraction pattern (or one-dimensional fast Fourier transform (FFT) pattern) revealed that the IMC layer was composed of Fe2Al5 or Fe4Al13 with a Fe/Al solid solution depending on the weld regions.

scholarly journals Comprehensive Analysis of the Microstructure and Mechanical Properties of Friction-Stir-Welded Low-Carbon High-Strength Steels with Tensile Strengths Ranging from 590 MPa to 1.5 GPa

2021 ◽  
Vol 11 (12) ◽  
pp. 5728
Author(s):  
HyeonJeong You ◽  
Minjung Kang ◽  
Sung Yi ◽  
Soongkeun Hyun ◽  
Cheolhee Kim
Keyword(s):  
Mechanical Properties ◽  
Tensile Test ◽  
Joint Strength ◽  
Solid Phase ◽  
Welding Process ◽  
High Strength Steels ◽  
High Strength ◽  
Low Carbon ◽  
Friction Stir ◽  
Welding Processes

High-strength steels are being increasingly employed in the automotive industry, requiring efficient welding processes. This study analyzed the materials and mechanical properties of high-strength automotive steels with strengths ranging from 590 MPa to 1500 MPa, subjected to friction stir welding (FSW), which is a solid-phase welding process. The high-strength steels were hardened by a high fraction of martensite, and the welds were composed of a recrystallized zone (RZ), a partially recrystallized zone (PRZ), a tempered zone (TZ), and an unaffected base metal (BM). The RZ exhibited a higher hardness than the BM and was fully martensitic when the BM strength was 980 MPa or higher. When the BM strength was 780 MPa or higher, the PRZ and TZ softened owing to tempered martensitic formation and were the fracture locations in the tensile test, whereas BM fracture occurred in the tensile test of the 590 MPa steel weld. The joint strength, determined by the hardness and width of the softened zone, increased and then saturated with an increase in the BM strength. From the results, we can conclude that the thermal history and size of the PRZ and TZ should be controlled to enhance the joint strength of automotive steels.

Study of the Key Issues of Friction Stir Welding of Titanium Alloy

2010 ◽  
Vol 638-642 ◽  
pp. 1185-1190 ◽  
Author(s):  
Hui Jie Liu ◽  
Li Zhou ◽  
Yong Xian Huang ◽  
Qi Wei Liu
Keyword(s):  
Titanium Alloy ◽  
Friction Stir Welding ◽  
Melting Point ◽  
Titanium Alloys ◽  
Welding Process ◽  
High Strength ◽  
Liquid Cooling ◽  
Friction Stir ◽  
Key Issues ◽  
Aluminum And Magnesium Alloys

As a new solid-state welding process, friction stir welding (FSW) has been successfully used for joining low melting point materials such as aluminum and magnesium alloys, but the FSW of high melting point materials such as steels and titanium alloys is still difficult to carry out because of their strict requirements for the FSW tool. Especially for the FSW of titanium alloys, some key technological issues need to solve further. In order to accomplish the FSW of titanium alloys, a specially designed tool system was made. The system was composed of W-Re pin tool, liquid cooling holder and shielding gas shroud. Prior to FSW, the Ti-6Al-4V alloy plates were thermo-hydrogen processed to reduce the deformation resistance and tool wear during the FSW. Based on this, the thermo-hydrogen processed Ti-6Al-4V alloy with different hydrogen content was friction stir welded, and the microstructural characterizations and mechanical properties of the joints were studied. Experimental results showed that the designed tool system can fulfill the requirements of the FSW of titanium alloys, and excellent weld formation and high-strength joint have been obtained from the titanium alloy plates.

Fatigue Behaviour of Friction Stir Welded Steel Joints

2014 ◽  
Vol 891-892 ◽  
pp. 1488-1493 ◽  
Author(s):  
José Azevedo ◽  
Virgínia Infante ◽  
Luisa Quintino ◽  
Jorge dos Santos
Keyword(s):  
Base Material ◽  
Welding Process ◽  
Steel Structures ◽  
Fatigue Behaviour ◽  
Fatigue Tests ◽  
Fatigue Properties ◽  
Welded Steel ◽  
Shipbuilding Industry ◽  
Friction Stir ◽  
Steel Joints

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.

Preparation of Triangular Silver Nanoparticles Using Polyvinyl Pyrrolidone with Different Concentration

2013 ◽  
Vol 873 ◽  
pp. 206-210
Author(s):  
Kai Li ◽  
Rao Fu ◽  
Qing Ran Gao ◽  
Ai Wei Tang ◽  
Ying Feng Wang
Keyword(s):  
Electron Microscopy ◽  
Aqueous Solution ◽  
Silver Nanoparticles ◽  
Driving Force ◽  
Ostwald Ripening ◽  
Polyvinyl Pyrrolidone ◽  
Protective Agent ◽  
Ag Nps ◽  
Transmission Electron ◽  
Uv Visible

This paper continues our previous work on preparation of triangular silver nanoparticles. The method proceeds with reaction of silver nitrate with hydrazine hydrate in the presence of polyvinyl pyrrolidone in aqueous solution. Effects of the concentration of PVP on the morphologies of Ag NPs were systematically investigated. The obtained Ag NPs were characterized by transmission electron microscopy and UV-visible spectrophotometer. The results showed that, triangular Ag NPs with edge lengths in the range of 50-200 nm were obtained using PVP as protective agent with lower concentration. As the concentration of PVP increased, spherical Ag NPs with their sizes about 6.2 nm were prepared and triangular Ag NPs were not obtained. The formation mechanism of triangular Ag NPs has been studied. Ostwald ripening is the driving force on the conversion of spherical Ag NPs to triangular Ag NPs in the presence of PVP.

Nucleation Mechanism of IGF in the HAZs of Ti-Killed HSLA Steel

2014 ◽  
Vol 898 ◽  
pp. 161-163
Author(s):  
Dong Ming Duan ◽  
Meng Xia Tang ◽  
Run Wu ◽  
Yong Bu ◽  
Xiao Chen
Keyword(s):  
Electron Microscope ◽  
Driving Force ◽  
Hsla Steel ◽  
High Strength ◽  
Nucleation Mechanism ◽  
Titanium Oxides ◽  
Lattice Matching ◽  
Transmission Electron ◽  
Thermodynamic Driving Force ◽  
Inert Substrate

The weldability of the steel can be improved by formation of intra-granular ferrite (IGF) in heat affected zones (HAZs) on the edge of weld bead. The nucleation mechanism of IGF of Ti-killed high strength low alloyed (HSLA) steel has already been investigated with the aid of transmission electron microscope. Titanium oxides (Ti2O3) particles with the diameter of 0.4μm and Si-rich complex inclusions (Ti3O5+MnS) with that of 0.5μm can serve as the nuclei of IGF. The nucleation mechanism of IGF is proposed as follows: (1) inclusions are inert substrate. (2) The depletion of the austenite former Mn local to the inclusion increases the thermodynamic driving force of γα for transformation. (3) Lattice matching between inclusion and ferrite reduces the interfacial energy of opposing nucleation.

On the problem of tool destruction when obtaining fixed joints of thick-walled aluminum alloy blanks by friction welding with mixing

2021 ◽  
Vol 23 (3) ◽  
pp. 72-83
Author(s):  
Kirill Kalashnikov ◽  
◽  
Andrey Chumaevskii ◽  
Tatiana Kalashnikova ◽  
Aleksey Ivanov ◽  
...  
Keyword(s):  
Aluminum Alloy ◽  
Friction Stir Welding ◽  
Friction Welding ◽  
Welding Process ◽  
High Strength ◽  
Heterogeneous Structure ◽  
Adhesive Interaction ◽  
Friction Stir ◽  
Tool Shoulder ◽  
Electric Erosion

Introduction. Among the technologies for manufacturing rocket and aircraft bodies, marine vessels, and vehicles, currently, more and more attention is paid to the technology of friction stir welding (FSW). First of all, the use of this technology is necessary where it is required to produce fixed joints of high-strength aluminum alloys. In this case, special attention should be paid to welding thick-walled blanks, as fixed joints with a thickness of 30.0 mm or more are the target products in the rocket-space and aviation industries. At the same time, it is most prone to the formation of defects due to uneven heat distribution throughout the height of the blank. It can lead to a violation of the adhesive interaction between the weld metal and the tool and can even lead to a destruction of the welding tool. The purpose of this work is to reveal regularities of welding tool destruction depending on parameters of friction stir welding process of aluminum alloy AA5056 fixed joints with a thickness of 35.0 mm. Following research methods were used in the work: the obtaining of fixed joints was carried out by friction welding with mixing, the production of samples for research was carried out by electric erosion cutting, the study of samples was carried out using optical metallography methods. Results and discussion. As a result of performed studies, it is revealed that samples of aluminum alloy with a thickness of 35.0 mm have a heterogeneous structure through the height of weld. There are the tool shoulder effect zone and the pin effect zone, in which certain whirling of weld material caused by the presence of grooves on tool surface is distinctly distinguished. It is shown that the zone of shoulders effect is the most exposed to the formation of tunnel-type defects because of low loading force and high welding speeds. It is revealed that tool destruction occurs tangentially to the surface of the tool grooves due to the high tool load and high welding speeds.

Application of Electric Current in Friction Stir Welding

2010 ◽  
Author(s):  
Matthew Pitschman ◽  
Jacob W. Dolecki ◽  
Garret W. Johns ◽  
Jun Zhou ◽  
John T. Roth
Keyword(s):  
Friction Stir Welding ◽  
Electric Current ◽  
Mechanical Energy ◽  
Welding Process ◽  
High Strength ◽  
Work Piece ◽  
Friction Stir ◽  
Weld Metals ◽  
Weld Properties ◽  
Electrically Enhanced

Friction Stir Welding (FSW) is a relatively new joining technique and has many applications. In FSW, heat generated due to friction between FSW tool and work-piece material softens the material and allows the materials in work-pieces to be stirred and joined together. FSW allows the work-pieces to be joined without reaching the melting point of the material, thus resulting in better welds. However, a large amount of mechanical energy has to be consumed for FSW of high-strength, difficult-to-weld metals such as titanium alloys. Hence, new FSW methods should be investigated to reduce the required energy. In this study, an innovative electrically-enhanced friction stir welding (EEFSW) has been developed. Electric current is passed in welding coupons of Aluminum 6061 plates and its effect on welding process and welds are examined. The results indicate that, with the aid of electric current, improvement in welding speed and reduction in energy consumption is obtainable, which enhances the productivity and widens the range of applications of FSW. Weld properties are found to be affected by the introduced current as well.

Effect of Processing Route on Mechanical Behavior of C-Mn Multiphase High Strength Cold Rolled Steel

2007 ◽  
Vol 539-543 ◽  
pp. 4375-4380
Author(s):  
Dagoberto Brandão Santos ◽  
Élida G. Neves ◽  
Elena V. Pereloma
Keyword(s):  
Electron Microscopy ◽  
Mechanical Properties ◽  
Mechanical Behavior ◽  
Quantitative Relationship ◽  
High Strength ◽  
Microstructural Characterization ◽  
Processing Route ◽  
Accelerated Cooling ◽  
Microstructural Parameters ◽  
Transmission Electron

The multiphase steels have complex microstructures containing polygonal ferrite, martensite, bainite, carbide and a small amount of retained austenite. This microstructure provides these steels with a high mechanical strength and good ductility. Different thermal cycles were simulated in the laboratory in order to create the microstructures with improved mechanical properties. The samples were heated to various annealing temperatures (740, 760 or 780°C), held for 300 s, and then quickly cooled to 600 or 500°C, where they were soaked for another 300 s and then submitted to the accelerated cooling process, with the rates in the range of 12-30°C/s. The microstructure was examined at the end of each processing route. The mechanical behavior evaluation was made by microhardness testing. The microstructural characterization involved optical microscopy (OM), X-ray diffraction (XRD), scanning electron microscopy (SEM) with electron backscattering diffraction (EBSD) and transmission electron microscopy (TEM). The use of multiple regression analysis allowed the establishment of quantitative relationship between the microstructural parameters, cooling rates and mechanical properties of the steel.

Influence of Tool Rotational Speed on the Mechanical Properties of Friction Stir Welded Al-Cu-Li Alloy

2016 ◽  
Vol 857 ◽  
pp. 228-231
Author(s):  
Ho Sung Lee ◽  
Ye Rim Lee ◽  
Kyung Ju Min
Keyword(s):  
Mechanical Properties ◽  
Friction Stir Welding ◽  
Space Shuttle ◽  
Welding Process ◽  
High Strength ◽  
Fusion Welding ◽  
Welding Parameters ◽  
Friction Stir ◽  
Mechanical And Microstructural Properties ◽  
Tool Rotation

Aluminum-Lithium alloys have been found to exhibit superior mechanical properties as compared to the conventional aerospace aluminum alloys in terms of high strength, high modulus, low density, good corrosion resistance and fracture toughness at cryogenic temperatures. Even though they do not form low-melting eutectics during fusion welding, there are still problems like porosity, solidification cracking, and loss of lithium. This is why solid state friction stir welding is important in this alloy. It is known that using Al-Cu-Li alloy and friction stir welding to super lightweight external tank for space shuttle, significant weight reduction has been achieved. The objective of this paper is to investigate the effect of friction stir tool rotation speed on mechanical and microstructural properties of Al-Cu-Li alloy. The plates were joined with friction stir welding process using different tool rotation speeds (300-800 rpm) and welding speeds (120-420 mm/min), which are the two prime welding parameters in this process.

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