Effects of friction stir welding on microstructure of 7075 aluminum
References (9)
- J.A. Wert
Scripta Met.
(1981) - W.M. Thomas
Friction Stir Butt Welding
(1995) - C. Dawes et al.
TWI Bulletin
(Nov./Dec. 1995) - M. Ellis et al.
TWI Bulletin
(Nov/Dec 1995)
Cited by (896)
This study investigates the influence of square and hexagon tool pin profiles on the butt joint of AA7075-T6 plates through friction stir welding. In contrast to the AA7075-T6 base metal with a grain size of 32.736 μm, both square (4.43 μm) and hexagon (5.79 μm) pin profiles led to a significant reduction in grain size within the stir zone (SZ) of the weld cross-section. The SZ region exhibited a gradient in recrystallization and a notable fraction of high angle grain boundaries, attributed to continuous dynamic recrystallization influenced by variations in temperature and strain rate. Pole figure analysis revealed predominant shear texture elements (B/ and C) with minor A1*/A2* and A/ , indicating elevated strains within the SZ. Orientation distribution function (ODF) analysis identified recrystallization texture elements such as Goss {110} <001>, cube {001} <101>, and P {011} <112>, along with shear texture components F {111} <112> and rotating cube (H) {001} <110>. Tensile and nanoindentation analyses demonstrated that the weld joint using a square-shaped pin profile exhibited higher strength, elongation, and elastic modulus compared to other weld joints. These findings suggest that the square tool pin geometry enhances material flow and grain refinement during welding, thereby improving the mechanical properties of the joint.
Sound dissimilar linear friction welding of A7075-T6 Al and mild steel by simultaneous interfacial deformation using higher forging speed
2024, Journal of Manufacturing ProcessesSound dissimilar welding of heat-treatable A7075-T6 aluminum and mild steel is extremely difficult due to the formation of interfacial cracks. The present study aims to attempt linear friction welding (LFW) of high-strength A7075-T6 Al alloy and mild steel to obtain sound joints with the highest strength ever by controlling the quality deteriorating phenomena that previous studies have faced. In this study, LFW joints were fabricated under two different applied pressures of 100 MPa and 300 MPa at a forging speed of 5 mm/s, along with various forging speeds ranging from 5 mm/s, 10 mm/s, to 20 mm/s under an applied pressure of 300 MPa, and the joint microstructure, mechanical properties and interface macrostructure were investigated. Furthermore, thermal dependence behaviors of both alloys were systematically investigated to optimize the processing parameters, especially applied pressure during LFW. At lower forging speeds of 5 mm/s and 10 mm/s, the weld defects and un-bonded regions were observed near the center of the weld accompanied by unevenness of butt surface due to the relatively thick intermetallic compound (IMC) formed in the interface which greatly influenced the joint strength. In contrast, at the higher forging speed of 20 mm/s, weld defects at the joint interface were effectively suppressed by promoting the simultaneous and uniform interfacial deformation of both alloys thanks to the extremely thin IMC during LFW. Consequently, a highly efficient joint with 100 % efficiency was successfully obtained at higher forging speed of 20 mm/s and despite the occurrence of softening towards A7075, the fabricated joint displayed a base metal fracture towards the steel side.
Microstructure and texture evolution of friction stir lap welded dissimilar multi‑aluminum stack
2023, Materials CharacterizationThis work investigates the microstructural evolution of a dissimilar multiple‑aluminum alloy stack (AA7055, AA7055, AA6022) produced by friction stir lap welding (FSLW). A through-thickness analyses of grain orientation map, grain size and distribution, strain distribution, and texture evolution by electron backscattered diffraction-based characterization technique were performed. Two different welding parameters (combination of tool rotation and traverse speed) were used to study the effects of the welding parameters on these microstructural characteristics. The study shows that higher welding speed and higher rotation speed of the FSLW tool yield finer grains. FSLW resulted in shear texture formation in the weld regions due to high welding speeds. This texture development in the nugget zone is consistent with shear deformation, and (111) pole figures show ideal shear texture components. The Stir Zone (SZ) exhibits shear texture (A/A ̅ and B/B ̅ components), consistent with other shear-assisted processes. Recrystallization mechanisms observed are CDRX in SZ and DDRX in TMAZ (Thermo-Mechanically Affected Zone). Interface analysis reveals the presence of oxide layers between different aluminum sheets, affecting joint mechanical performance. The mechanical property of the lap welded joints was presented in terms of microhardness distribution across the weld cross section. Slightly higher hardness in higher speed welding setup was observed throughout the SZ and AA6022 layer, indicating greater grain refinement and uniform grain structure distribution.
On improved fatigue properties of aluminum alloy 5086 weld joints
2023, International Journal of FatigueIn this work, we aimed to investigate the fatigue properties of AA5086-H321 and its weld joints. The AA5086-H321 plates were welded in a butt configuration using the friction stir welding. Load-controlled axial sinusoidal cyclic tests were conducted in the ambient conditions, at a frequency 20 Hz, and at different load ratios i.e., , 0.1, and 0.5. The weld joints, in general, are known to have reduced properties. However, in this study, the base alloy and its weld joint had similar hardness and ultimate tensile strength, but with marginally reduced elongation (). The endurance limits of the weld joints were either higher ( and at and , respectively) or same (at ) as compared to that of the base alloy. The difference in fatigue lives of base alloy and its weld joint kept diminishing with increasing R-ratio. Microscopic examination of fracture surfaces in weld joints revealed three types of crack initiations: voids, inclusions, and tool-marks, and two types of crack propagation mechanisms: intergranular and transgranular. However, in base alloys, only defect-free surface initiation with transgranular crack growth was observed. Mean stress, as expected, had a detrimental effect on fatigue properties, with no definitive control on the type of crack initiation or its propagation mechanism. An increase in the fatigue lives of weld joints was attributed to the crack growth retardation during the intergranular fatigue crack propagation due to frequent defection of crack path, which was absent in the base alloys. Most of the intergranular facets were observed near the surfaces (top or bottom) of the weld nugget zone and disappeared when the crack front reaches its interface boundary with the heat affected zone. All these aspects of fatigue damage in microstructurally heterogeneous weld joints and the plausible explanations for the observed mechanical fatigue properties are presented in this study.
Study of microstructure evolution of friction stir welded novel (Al-Zn-Mg)-Fe (HE700) cast alloys for automotive applications
2023, Materials Science and Engineering: ALight weighting of automobiles would improve fuel efficiency and reduce emissions. Newly developed high-strength, high-elongation (Al-Zn-Mg)-Fe alloys for structural shape casting applications have the potential to fulfill the demand for significant lightweighting of components. Joining such shape casting alloys to form a high integrity component assembly is a critical process in structural lightweighting. Friction stir welding has recently emerged as an effective joining method for aluminium alloys. In this work, friction stir welding was used to join these new-generation (Al-Zn-Mg)-Fe cast alloys. The critical process parameters such as rotation and traverse speed were optimized through a detailed microstructural study and mechanical property evaluation of the welds. Three different tool rotation speeds (600, 800, and 1000 rpm) and traverse speeds (25, 50, and 75 mm/min) were the independent parameters. The welds made with 800 rpm and 25 mm/min traverse speed showed the best properties with no weld/microstructural defects. Friction stir welding also refined the microstructure and uniformly distributed the agglomerated Al-Fe-based intermetallic particles. The microhardness and tensile properties (longitudinal direction) of the stir zone increased significantly (Ultimate tensile strength = 380 MPa, Yield strength = 250 MPa) with appreciable ductility (31%) due to the microstructural refinement despite the dissolution of the strengthening precipitates such as Guinier-Preston zones and ηꞌ phases. The study was able to establish a viable window of processing parameters for joining the new generation Al-Zn-Mg-Fe alloys for structural lightweight components.
The effects of friction stir welding on microstructure and formability of 7075-T6 sheet
2023, Results in EngineeringThe present research aims to investigate the effects of friction stir welding (FSW) on the microstructure and mechanical properties of 7075-T6 aluminum alloy thin sheets. The welding has been performed perpendicular to the rolling direction of the sheets at three rotational speeds of 600, 1000, and 1600 rpm. From mechanical and microstructural points of view, a suitable welding condition has been recognized at 1000 rpm and welding speed of 50 mm/min. It is observed that with increasing the welding rotational speed more precipitates of the base metal are being dissolved in the metallic matrix and their distribution is more uniform. This phenomenon is recognized as the main mechanism of mechanical properties decline at 1600 rpm. Surprisingly 15,000 h after the welding process, the natural aging could not recover the precipitations within the welding zone of the specimen welded by 1600 rpm rotational speed. The effects of FSW on the three-dimensional forming behavior of the joints have been examined by the hemispherical punch stretching (HPS) method. Forming limit diagrams (FLD) of the weldments and the starting material have been measured and compared to each other. The formability examinations have demonstrated a 40% decline in the forming limit of the welded specimens in comparison to the base metal. The main reasons for the smaller formability of the welded specimens are comprehensively discussed.