Friction Stir Processed AA5182-O and AA6111-T4 Aluminum Alloys. Part 2: Tensile Properties and Strain Field Evolution (original) (raw)
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Journal of Materials Engineering and Performance, 2007
The present article is the first part in a two-part series in which crystallographic texture developed during friction stir processing of AA5182-O and AA6111-T4 is characterized and its impact on tensile properties explored. For the texture measurements, coupons were cut from the friction stir processed zone at selected orientations relative to the direction of tool translation. Texture was characterized with electron backscatter diffraction (EBSD) in a scanning electron microscope. Measurements were made at key positions along the coupon surfaces and texture differences between the two friction stir processed Al alloys are discussed in detail. Grain size variations were also measured in both the base and friction stir processed materials and subsequently compared. In part 2, a state-of-art digital image correlation technique is used to investigate tensile properties of both friction stir processed Al alloys. The impact of crystallographic texture on mechanical properties is also explored in this latter part.
Heterogeneity of crystallographic texture in friction stir welds of aluminum
Metallurgical and Materials Transactions A, 2001
Over the past decade, friction stir welding (FSW) has rapidly become an important industrial joining process, particularly in the aluminum industry. Included among the advantages of FSW are such important attributes as improved weld strength and the elimination of cracking and porosity. During the friction stir process, the metal undergoes a tortuous deformation path that is not yet fully understood. The crystallographic texture that evolves during FSW contains sharp spatial gradients that undoubtedly influence the integrity of the weld and surrounding region in subsequent performance. The locally measured textures are discussed in the context of the material flow required to produce such textures, ultimately resulting in an estimate of the flow field present during FSW. DAVID P. FIELD, Assistant Professor, is with the School of Mechanical rotational speed of 700 rpm and a travel rate of 18 cm/min or a rotational speed of 1200 rpm and a travel rate of 58 99164-2920. TRACY W. NELSON, Assistant Professor, and YURI HOVANSKI, Graduate Student, are with the Department of Mechanical cm/min. Weld parameters for the C458 were 600 rpm and Engineering, Brigham Young University, Provo, UT 84604. KUMAR V. 13 cm/min. JATA, Senior Researcher Materials Scientist, is with the Materials and Orientation imaging analysis was performed on entire Manufacturing Directorate, Air Force Research Laboratory, AFRL/MLLM, weld regions on cross sections of the welds. In addition, Wright-Patterson Air Force Base, OH 45433.
Microstructural characterisation of friction stir processed aluminium
Materials Science and Technology, 2011
Friction stir processing was carried out on commercially pure aluminium, and a detailed microstructural characterisation was performed by electron backscattered diffraction and transmission electron microscopy. Friction stir processing resulted in significant grain refinement with narrow grain size distribution. The microstructure showed fine and equiaxed grains, with some ultrafine grains being also observed. Electron backscattered diffraction studies showed majority of the boundaries to be high angle, confirming the occurrence of dynamic recrystallisation (DRX). Transmission electron microscopy observations revealed dislocation arrangement into subgrain boundaries, grains having different dislocation densities and in different stages/degrees of recovery. Electron backscattered diffraction analysis also revealed a progressive transformation of sub-grain boundaries into high angle grain boundaries. A multimechanism of dynamic recovery, continuous DRX and discontinuous DRX seems to be operating during the process. The microstructure is not affected by changing the rotation speed from 640 to 800 rev min 21 , except that the grain size was marginally larger for higher rotational speed.
Metals
This work investigated the effect of friction stir welding (FSW) tool rotation rate and welding speed on the grain structure evolution in the nugget zone through the thickness of the 10 mm thick AA5083/AA5754 weldments. Three joints were produced at different combinations of FSW parameters. The grain structure and texture were investigated using electron backscattering diffraction (EBSD). In addition, both the hardness and tensile properties were investigated. It was found that the grain size varied through the thickness in the nugget (NG), which was reduced from the top to the base in all welds. Reducing the rotation rate from 600 rpm to 400 rpm at a constant welding speed of 60 mm/min reduced the average grain size from 33 µm to 25 µm at the top and from 19 µm to 12 µm at the base. On the other hand, the increase of the welding speed from 20 mm/min to 60 mm/min had no obvious effect on the average grain size. This implied that the rotation rate was more effective in grain size red...
12th International Conference on Mining, Petroleum and Metallurgical Engineering, 2014
In this study, a 10 mm thick AA7020 plate is friction stir processed (FSP) to a depth of 6mm using two different tool geometries of threaded and unthreaded pin and different friction stir processing speeds of 20, 40, 60 and 80 mm/min at tool rotation rate of 560rpm. The microstructure is investigated initially using optical microscopy. The mechanical properties of the processed material are characterized using tension testing and hardness testing. The tension test is carried out along the FSP direction and the hardness is measured mainly for the processed zone and compared with the base material. Microstructure investigation showed significant grain refining in the processed zone. In all the conditions studied, the processed zone showed a lower hardness as compared to the base metal. This suggests the dissolution of precipitate particles due to the frictional heat that softens the material. The tensile strength of the FS processed specimens was significantly increased by up to 14% as compared to the base metal. All specimens invariably showed considerable increases in the ductility by up to 75%. The use of the unthreaded pin showed better ductility and strength.
Materials Science and Engineering: A, 2006
Residual stresses were measured through the thickness of friction-stir processed (FSP) 6061-T6 aluminum-alloy plates using neutron diffraction. Two different specimens were prepared to study the relationship between residual stress distributions through the thickness of the plate and angular distortion: (Case 1) a plate processed with both stirring pin and tool shoulder, i.e., a typical FSP plate subjected to both plastic deformation and frictional heat, and (Case 2) a plate processed only with the tool shoulder, i.e., subjected mainly to the frictional heating. The measured residual stress profiles show relatively small through-thickness residual stress variations in Case 1, while there is a significant through-thickness residual stress variations in Case 2. The main cause of the geometric angular distortion could be related to the non-uniform distribution of the frictional heat generated by the tool shoulder leading to the asymmetric distributions of the residual stress through the thickness of the FSP plate.
Microstructural and Mechanical Characterization of Friction Stir Processed 5086 Aluminum Alloy
In the present investigation friction stir processing (FSP) is carried out by single and multipass FSP on a 5086 aluminum alloy to modify microstructure and mechanical properties. The processing is carried out at constant rotation speed of 1025 rpm and at a traverse speed of 30 mm/min. Inhomogeneous microstructural distribution was observed across the processed zone. EBSD analysis has been done to evaluate the microstructure. Overlapping passes is showing same grain size as in single pass FSPed material. Material processed using multi pass FSP at 30 mm/min is showing higher mechanical strength as compared to base material. The bulk material produced due to multipass seems to be good for superplastic forming applications.
Samples with one through three passes with 100% overlap were created using friction stir processing (FSP) in order to locally modify the microstructural and mechanical properties of 6082-T6 Aluminum Alloy. A constant rotational speed and three different traverse speeds were used for processing. In this article, the microstructural properties in terms of grain structure and second phase particles distribution, and also the mechanical properties in terms of hardness and tensile strength of the processed zone were addressed with respect to the number of passes and traverse speeds. The parameter combination which resulted in highest ultimate tensile strength was further compared with additional two rotation speeds. FSP caused dynamic recrystallization of the stir zone leading to equiaxed grains with high angle grain boundaries which increased with increasing the number of passes. The accumulated heat accompanying multiple passes resulted in increase in the grain size, dissolution of precipitates and fragmentation of second phase particles. Increasing the traverse speed on the other hand did not affect the grain size, yet reduced the particles size as well as increased the particle area fraction. Hardness and tensile test results of the stir zone were in good agreement where increasing the number of passes caused softening and reduction of the ultimate tensile strength, whereas, increasing the traverse speed increased the strength and hardness. Increasing the tool rotational speed did not have a significant influence on particle mean diameter, ultimate tensile strength and hardness values of the stir zone, whereas, it caused an increase in mean grain size as well as particle area fraction.
Materials
The Friction-Assisted Lateral Extrusion Process (FALEP) is a severe plastic deformation (SPD) technique for producing metal sheets from bulk metal or powder in one single deformation step at room temperature. In the present work, aluminum Al-1050 was deformed by FALEP. Then, its microstructure was examined by EBSD; the crystallographic texture by X-ray; material strength, ductility, and the Lankford parameter by tensile testing; the latter also by polycrystal plasticity simulations. It is shown that the microstructure was highly refined, with the grain size reduced more than 160 times down to 600 nm under the imposed shear strain of 20. The obtained texture was a characteristic simple shear texture with a shear plane nearly parallel to the plane of the sheet. The yield and ultimate strengths increased by about 10 times and three times, respectively. The Lankford parameter was 1.28, which is very high for aluminum, and due to the specific shear texture, unusual in a sheet. All these ...