Microstructure and mechanical characterization of tungsten inert gas-welded joint of AA6061 and AA7075 by friction stir processing

Author(s):  
Husain Mehdi ◽  
RS Mishra

In this work, the effect of friction stir processing (FSP) on tungsten inert gas welding (TIG) has been observed to improve mechanical properties and wear resistance behavior of TIG-welded joint of AA7075 and AA6061. The TIG-welded joints were processed by FSP at various tool rotational speeds of 700, 800, 900, 1000, and 1100 r/min with a constant feed rate of 70 mm/min and tilt angle of 1°. The maximum joint efficiency of 92.81% was observed in TIG + FSP-welded joint with filler ER5356 at a rotational tool speed of 1100 r/min. The maximum tensile strength of 284 MPa was observed in TIG + FSP-welded joint with filler ER5356, whereas the minimum tensile strength of 124 MPa was observed in the TIG weldment with filler ER4043. The cleavage facets, tears ridges, and large dimples were observed in fractured specimens of TIG-welded joints, whereas fine and equiaxed dimples were observed in TIG + FSP-welded joints. The maximum micro-hardness of 137 HV in the stir zone was observed in TIG + FSP-welded joint at a rotational tool speed of 1100 r/min. Due to intense precipitate (MgZn2) kept in the stir zone with filler ER5356, the TIG + FSP-welded joints using filler ER5356 have superior wear resistance compared to TIG and TIG + FSP-welded joint with filler ER4043.

Metals ◽  
2020 ◽  
Vol 10 (1) ◽  
pp. 142 ◽  
Author(s):  
Sipokazi Mabuwa ◽  
Velaphi Msomi

There is an increase in reducing the weight of structures through the use of aluminium alloys in different industries like aerospace, automotive, etc. This growing interest will lead towards using dissimilar aluminium alloys which will require welding. Currently, tungsten inert gas welding and friction stir welding are the well-known techniques suitable for joining dissimilar aluminium alloys. The welding of dissimilar alloys has its own dynamics which impact on the quality of the weld. This then suggests that there should be a process which can be used to improve the welds of dissimilar alloys post their production. Friction stir processing is viewed as one of the techniques that could be used to improve the mechanical properties of a material. This paper reports on the status and the advancement of friction stir welding, tungsten inert gas welding and the friction stir processing technique. It further looks at the variation use of friction stir processing on tungsten inert gas and friction stir welded joints with the purpose of identifying the knowledge gap.


Author(s):  
Mahmoud Abbasi ◽  
Mohammad Givi ◽  
Behrouz Bagheri

Tungsten inert gas welding method is widely used to weld aluminum alloys. However, the development of some defects such as porosity and undercutting which form during tungsten inert gas welding may decrease the quality of the weld. Processing of the joint by friction stir processing is a method to enhance weld quality. In the current work, the weld area produced by tungsten inert gas is processed by friction stir processing as well as a novel processing method entitled “friction stir vibration processing.” In friction stir vibration processing, the specimen is vibrated while friction stir processing is carried out. The results show that both processing methods lead to grain refinement in the weld region and increase the strength and ductility of the tungsten inert gas–welded specimen. The stir zone grain sizes of friction stir vibration–processed samples are less than those of friction stir–processed ones. It is believed that workpiece vibration in friction stir vibration processing increases the material straining and intensifies the dynamic recrystallization. By application of friction stir processing on tungsten inert gas–welded specimen, ultimate tensile strength and ductility increase by about 10% and 22%, respectively. They increase by about 17% and 33%, respectively, as friction stir vibration processing is applied. The results also indicate that the effect of friction stir vibration processing on the microstructure of the weld region and its mechanical properties increases as vibration frequency increases. Friction stir vibration processing is a good alternative for friction stir processing, and it is recommended for application in industry.


2019 ◽  
Vol 2019 ◽  
pp. 1-14 ◽  
Author(s):  
Sipokazi Mabuwa ◽  
Velaphi Msomi

This paper presents the analysis of the friction stir-processed aluminium alloy 5083-H111 gas tungsten arc-welded and friction stir-welded joints. The comparative analysis was performed on the processed and unprocessed gas tungsten arc-welded and friction stir-welded joints of similar aluminium alloy 5083-H111. The results showed a clear distinction between the friction stir processed joints and unprocessed joints. There is a good correlation observed between the microstructural results and the tensile results. Ultrafine grain sizes of 4.62 μm and 7.177 μm were observed on the microstructure of the friction stir-processed friction stir-welded and gas tungsten arc-welded joints. The ultimate tensile strength for friction stir-welded and gas tungsten arc-welded before friction stir processing was 153.75 and 262.083 MPa, respectively. The ultimate tensile strength for friction stir processed friction stir-welded joint was 303.153 MPa and gas tungsten arc-welded joints one was 249.917 MPa. The microhardness values for the unprocessed friction stir-welded and gas tungsten arc-welded joints were both approximately 87 HV, while those of the friction stir-processed ones were 86.5 and 86 HV, respectively. The application of friction stir processing transformed the gas tungsten arc morphology from brittle to ductile dimples and reduced the ductile dimple size of the unprocessed friction stir-welded joints from the range of 4.90–38.33 μm to 3.35–15.59 μm.


2020 ◽  
Vol 62 (8) ◽  
pp. 793-802
Author(s):  
Şefika Kasman ◽  
Sertan Ozan

Abstract In the present study, AA 2024-T351 plates with a thickness of 6 mm were joined using the friction stir welding technique with three different tool rotational speeds and two different pin profiles. Microstructural features and mechanical properties of welded joints were investigated. The grains in recrystallized regions along the stir zone were observed to be almost with invariable sizes. The grain size was revealed to increase with the increase in tool rotational speed. The average grain size was observed to dramatically increase from 2.3 μm to 5.6 μm for welded joints produced with pentagonal shaped pin. All the welded joints were observed to contain defects; the presence of defects exhibited a negative effect on the tensile properties of the welded joint. Most of the defects were observed to localize at the root region of joints. The joint, welded with the tool rotational speed of 250 rpm using pentagonal shaped pin, exhibited ultimate tensile strength with a value of 365 MPa. The ultimate tensile strength of welded joints was found to be higher with the decrease in the tool rotational speed. The welding efficiency of joints was compared with the ultimate tensile strength of base metal; notably, welding efficiency values between 46 % and 80 % were achieved. Microstructural characterizations revealed that Al2Cu (θ phase), Al2CuMg (S phase), and AlCuFeMnSi, Al7Cu2Fe intermetallic particles were dispersed in the stir zone.


Author(s):  
Mostafa Akbari ◽  
Parviz Asadi

Multi-walled carbon nanotube/aluminum composites are fabricated on Al–Si cast alloy employing friction stir processing. First, the microstructure of the stir zone, as well as the effect of process parameters on the size of silicon particles, is investigated. Then, the process is numerically simulated using a thermo-mechanically coupled three-dimensional finite element method model. Material flow, as the primary reason for the dispersion of reinforcing particles, is considered in the numerical model, and proper conditions to obtain a uniform dispersion of multi-walled carbon nanotubes are determined. Scanning electron microscope analysis is carried out to consider the particle distribution in the texture of the stir zone. The results show that the particle distribution improves significantly by changing the tool rotation direction between the friction stir processing passes. The hardness test is accomplished on the cross-section of the friction stir processed specimens, and finally, the wear test is performed to compare the wear resistance of the composites with the base alloy. The results show that the wear resistance and hardness of the produced composites are considerably enhanced compared to the base alloy.


2011 ◽  
Vol 189-193 ◽  
pp. 3601-3604 ◽  
Author(s):  
Ye Hua Jiang ◽  
De Hong Lu ◽  
Ming Zhou ◽  
Shao Sheng Wei ◽  
Rong Zhou

Friction stir processing (FSP) was applied to modify the surface of a hypereutectic alloy Al-30wt.%Si, the influence of FSP passes on the size and morphology of Si particles, the mechanical properties of the materials in the stir zone was investigated. In the nugget by FSP, the silicon particles were intensely refined to several micrometers and spheroidized, and the refinement and spheroidization degree increased with FSP passes. The tensile behavior of the alloy by FSP has typically plastic feature. With FSP passes increasing, the tensile strength and the elongation increased gradually, and the improvement ratio of the elongation is more obvious. The improvement is attributed to the spheroidization and refinement of silicon particles by FSP.


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