Stability of nugget zone grain structures in high strength Al-alloy friction stir welds during solution treatment

In this study, 2A14-T4 Al-alloy T-joints were prepared via stationary shoulder friction stir welding (SSFSW) technology where the stirring pin’s rotation speed was set as different values. In combination with the numerical simulation results, the macro-forming, microstructure, and mechanical properties of the joints under different welding conditions were analyzed. The results show that the thermal cycle curves in the SSFSW process are featured by a steep climb and slow decreasing variation trends. As the stirring pin’s rotation speed increased, the grooves on the weld surface became more obvious. The base and rib plates exhibit W- or N-shaped hardness distribution patterns. The hardness of the weld nugget zone (WNZ) was high but was lower than that of the base material. The second weld’s annealing effect contributed to the precipitation and coarsening of the precipitated phase in the first weld nugget zone (WNZ1). The hardness of the heat affect zone (HAZ) in the vicinity of the thermo-mechanically affected zone (TMAZ) dropped to the minimum. As the stirring pin's rotation speed increased, the tensile strengths of the base and rib plates first increased and then dropped. The base and rib plates exhibited ductile and brittle/ductile fracture patterns, respectively.

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Microstructure and Mechanical Properties of a Friction Stir Processed Al-Zn-Mg-Cu Alloy

Materials Science Forum ◽

10.4028/www.scientific.net/msf.654-656.1428 ◽

2010 ◽

Vol 654-656 ◽

pp. 1428-1431 ◽

Cited By ~ 1

Author(s):

Margarita Vargas ◽

Sri Lathabai

Keyword(s):

Mechanical Properties ◽

Rotational Speed ◽

High Strength ◽

Travel Speed ◽

Nugget Zone ◽

Friction Stir ◽

Complex Interactions ◽

Cu Alloy ◽

Microstructure And Mechanical Properties ◽

Aa 7075

Friction stir processing (FSP) was performed on AA 7075-T6, a heat treatable high strength Al-Zn-Mg-Cu alloy. The two main FSP parameters, the tool rotational and travel speed, were varied systematically in order to understand their influence on the microstructure and mechanical properties of the processed zone. At a given rotational speed, increasing the travel speed increased the microhardness of the nugget (stir) zone; for a given travel speed there appeared to be an optimum rotational speed which resulted in the highest microhardness. The range of FSP parameters used did not significantly influence the nugget zone grain size. It is suggested that the observed mechanical properties are a result of the complex interactions between the FSP thermo-mechanical effects and the processes of dissolution, coarsening and re-precipitation of the strengthening precipitates in this alloy.

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Experimental Estimation of Strain Rate during FSW of Al-Alloy Using Plane-Strain Compression

Materials Science Forum ◽

10.4028/www.scientific.net/msf.580-582.299 ◽

2008 ◽

Vol 580-582 ◽

pp. 299-302 ◽

Cited By ~ 3

Author(s):

Kunitaka Masaki ◽

Yutaka S. Sato ◽

Masakatsu Maeda ◽

Hiroyuki Kokawa

Keyword(s):

Strain Rate ◽

Plane Strain ◽

Travel Speed ◽

Plane Strain Compression ◽

Stir Zone ◽

Grain Structure ◽

Al Alloy ◽

Strain Rates ◽

Friction Stir ◽

Grain Structures

Friction stir welding (FSW) makes the stir zone with fine recrystallized grain structure. The recrystallized grains would be formed through dynamic recrystallization at high temperatures and high strain-rate. The present study experimentally simulated the dynamically recrystallized microstructure of a friction stir welded Al alloy 1050 produced at 600 rpm rotation and 100 mm/min travel speed, using combination of the plane-strain compression at various strain rates and the subsequent cooling along the cooling cycle of FSW. The equiaxed grain structures similar to the microstructure of the stir zone were produced at strain rates between 0.1 and 32 s-1; the grain size decreased with increasing strain rate. Strain rate during the FSW could be estimated to be about 1.8 s-1. The present study suggests that plane-strain compression test can simulate the recrystallized grain structure of the friction stir welds.

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Effect of Welding Speed on Mechanical Properties of Friction Stir Welded AA 6082-T6 Al Alloy

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.877.98 ◽

2018 ◽

Vol 877 ◽

pp. 98-103

Author(s):

Dhananjayulu Avula ◽

D.K. Dwivedi

Keyword(s):

Tensile Strength ◽

Welding Speed ◽

Welded Joint ◽

Al Alloy ◽

Microstructural Properties ◽

Nugget Zone ◽

Percentage Elongation ◽

Friction Stir ◽

Mechanical And Microstructural Properties ◽

Hardness Values

In this study the effect of process parameters on mechanical and microstructural properties of similar AA6082-T6 joints produced by friction stir welding was investigated. Different samples were produced by varying the transverse welding speeds of the tool from 19 to 75 mm/min and a fixed rotational speed of 635 rpm. A more uniform hardness values in the nugget zone were observed at 48 mm/min welding speed. The lowest hardness values were recorded on nugget zone at all the welding speeds. The increase in welding speed increases ultimate tensile strength and reaches maximum and further increase in welding speed results decrease in tensile strength were observed. The welded joint has highest joint efficiency (52.33 %) obtained at the welding speed of 48 mm/min. Similarly with the increase in welding speed decrease in the percentage elongation were recorded.

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Effect of cyclic solution treatment on microstructure and mechanical properties of friction stir welded 7075 Al alloy

Materials Science and Engineering A ◽

10.1016/j.msea.2015.10.010 ◽

2016 ◽

Vol 649 ◽

pp. 293-300 ◽

Cited By ~ 43

Author(s):

S.M. Bayazid ◽

H. Farhangi ◽

H. Asgharzadeh ◽

L. Radan ◽

A. Ghahramani ◽

...

Keyword(s):

Mechanical Properties ◽

Solution Treatment ◽

Al Alloy ◽

Friction Stir ◽

7075 Al Alloy ◽

Microstructure And Mechanical Properties

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Friction Stir Welds of Al Alloy-Cu: An Investigation on Effect of Plunge Depth

Archive of Mechanical Engineering ◽

10.1515/meceng-2016-0035 ◽

2016 ◽

Vol 63 (4) ◽

pp. 619-634 ◽

Cited By ~ 18

Author(s):

Mohd Atif Wahid ◽

Arshad Noor Siddiquee ◽

Zahid Akhtar Khan ◽

Mohammad Asjad

Keyword(s):

Mechanical Properties ◽

Tensile Properties ◽

Pure Copper ◽

Al Alloy ◽

Base Metals ◽

Mixed Structure ◽

Nugget Zone ◽

Butt Joints ◽

Plunge Depth ◽

Friction Stir

Abstract In the present study, butt joints of aluminum (Al) 8011-H18 and pure copper (Cu) were produced by friction stir welding (FSW) and the effect of plunge depth on surface morphology, microstructure and mechanical properties were investigated. The welds were produced by varying the plunge depth in a range from 0.1 mm to 0.25 mm. The defect-free joints were obtained when the Cu plate was fixed at the advancing side. It was found that less plunging depth gives better tensile properties compare to higher plunging depth because at higher plunging depth local thinning occurs at the welded region. Good tensile properties were achieved at plunge depth of 0.2 mm and the tensile strength was found to be higher than the strength of the Al (weaker of the two base metals). Microstructure study revealed that the metal close to copper side in the Nugget Zone (NZ) possessed lamellar alternating structure. However, mixed structure of Cu and Al existed in the aluminum side of NZ. Higher microhardness values were witnessed at the joint interfaces resulting from plastic deformation and the presence of intermetallics.

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Microstructure and Mechanical Properties of Dissimilar Friction Stir Welded AA2024-T4/AA7075-T6 T-Butt Joints

Metals ◽

10.3390/met11010128 ◽

2021 ◽

Vol 11 (1) ◽

pp. 128

Author(s):

Mohamed M.Z. Ahmed ◽

Mohamed M. El-Sayed Seleman ◽

Zeinab A. Zidan ◽

Rashad M. Ramadan ◽

Sabbah Ataya ◽

...

Keyword(s):

Aluminum Alloys ◽

High Strength ◽

Travel Speed ◽

Nugget Zone ◽

Butt Joints ◽

Friction Stir ◽

Aircraft Skin ◽

Ebsd Technique ◽

High Strength Aluminum Alloys ◽

Electron Back Scattered Diffraction

Aircraft skin and stringer elements are typically fabricated from 2xxx and 7xxx series high strength aluminum alloys. A single friction stir welding (FSW) pass using a specially designed tool with shoulder/pin diameter ratio (D/d) of 3.20 is used to produce dissimilar T-butt welds between AA2024-T4 and AA7075-T6 aluminum alloys at a constant travel speed of 50 mm/min and different rotational speeds of 400, 600 and 800 rpm. The AA2024-T4 is the skin and the AA7075-T6 is the stringer. Sound joints are produced without macro defects in both the weld top surfaces and the joint corners at all rotational speeds used (400, 600, and 800 rpm). The hardness value of the nugget zone increases by increasing the rotational speed from 150 ± 4 Hv at 400 rpm to 167 ± 3 Hv at 600 rpm, while decreases to reach the as-received AA2024-T4 hardness value (132 ± 3 Hv) at 800 rpm. Joint efficiency along the skin exhibits higher values than that along the stringer. Four morphologies of precipitates were detected in the stir zone (SZ); irregular, almost-spherical, spherical and rod-like. Investigations by electron back scattered diffraction (EBSD) technique showed significant grain refinement in the sir zone of the T-welds compared with the as-received aluminum alloys at 600 rpm due to dynamic recrystallization. The grain size reduction percentages reach 85 and 90 % for AA2024 and AA7075 regions in the mixed zone, respectively. Fracture surfaces along the skin and stringer of T-welds indicate that the joints failed through mixed modes of fracture.

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