Effect of Cold Rolling on the Mechanical Properties and Formability of FSWed Sheets in AA5754-H114

Self Cite

Friction stir welding (FSW) is the most widely used solid-state joining technique for light-weight plate and sheet products. This new joining technique is considered an energy-saving, environment friendly, and relatively versatile technology. FSW has been found to be a reliable joining technique in high-demand technology fields, such as high-strength aerospace aluminum and titanium alloys, and for other metallic alloys that are hard to weld by conventional fusion welding. Several studies accounted for the microstructural modifications induced by solid-state FSW, based on the resulting mechanical properties obtained at the FSW joints, such as tensile, bending, torsion, ductility and fatigue responses. In the last few years with the need and emerging urgency to widen the FSW application fields, broadening the possible alloy systems, and to optimize the resulting mechanical properties, this joining technique was further developed. In this respect, the present contribution focuses on two modified-FSW techniques and approaches applied to aluminum alloys plates. In a first case, an age-hardening AA6082 sheets were double side friction stir welded (DS-FSW). In a second case a non-age-hardening AA5754 sheet was FSW by an innovative approach in which welding pin was forced to slightly deviate away from the joining centreline (defined by authors as RT). In both the cases different pin heights were used, the sheets were subjected to heat treatments (peak hardening T6 for the AA6082, and annealing for the AA5754) and compared to the non-heat treated FSW conditions. Microstructural modifications were characterized by optical microscopy (OM). The mechanical properties were characterized both locally, by nanoindentation techniques, and globally, by tensile (yield, YT; ultimate, UT; and elongation, El) or forming limit curve (FLC) tests. Both the new approaches were directly compared to the conventional FSW techniques in terms of resulting microstructures and mechanical responses.

Section: Double Side Friction Stir Welding Methodologymentioning

confidence: 99%

New Approaches to Friction Stir Welding of Aluminum Light-Alloys

Cabibbo

Forcellese

Santecchia

et al. 2020

Self Cite

“…Conversely, too low rotational speed and too high welding speed tend to provide insufficient heat inputs to soften materials. As a result, other kinds of defects, including tunnel, voids, and microcracks in weld bead [14][15][16][17][18][19] can appear. Similarly, other welding parameters can provide improper heat input and metal intermixing.…”

Section: Introductionmentioning

confidence: 99%

Main Issues in Quality of Friction Stir Welding Joints of Aluminum Alloy and Steel Sheets

Safeen

Spena

2019

Joining of aluminum alloys through friction stir welding (FSW) is effectively employed in several industries (e.g., aeronautics and aerospace) since it guarantees proper weld strength as compared to other joining technologies. Contrarily, dissimilar FSW of aluminum alloys and steels often poses important issues in the selection of welding parameters due to the difficulty to join different materials. Improper welding parameters give rise to the formation of intermetallic compounds, and internal and external defects (e.g., tunnel formation, voids, surface grooves, and flash). Intermetallic compounds are brittle precipitates of Al/Fe, which chiefly initiate crack nucleation, whereas internal and external defects mainly act as stress concentration factors. All these features significantly reduce joint strength under static and dynamic loading conditions. With reference to the literature, the influence of main welding parameters (rotational speed, welding speed, tool geometry, tilt angle, offset distance, and plunge depth) on the formation of intermetallic compounds and defects in FSW of aluminum alloys and steels is discussed here. Possible countermeasures to avoid or limit the above-mentioned issues are also summarily reported.

“…In particular, Casalino et al studied the influence of process parameters on the mechanical properties of FSWed joints in AA6082-T6 and the relationships among the ultimate tensile strength, ultimate elongation and vertical force applied during process [6]. Furthermore, Casalino et al investigated the mechanical properties and formability of FSWed joints in AA5754-H114 after cold rolling performed in order to remove the forging effect, due to the vertical force applied by the tool, in order to ensure a constant thickness of the welded blank [16]. Peng et al studied the microstructures, tensile properties, hardness distribution, and fracture features of dissimilar FSWed joints in AA5A06 and AA6061 under different process conditions [17].…”

Section: Introductionmentioning

confidence: 99%

High-Speed Deformation of Pinless FSWed Thin Sheets in AA6082 Alloy

Forcellese

Simoncini

2019

Self Cite

The high-speed deformation behavior of friction stir-welded thin sheets in AA6082-T6 aluminum alloy, under biaxial balanced stretching, was investigated by means of a hemispherical punch test carried out using direct tension-compression Split Hopkinson Bar. The friction stir welding process was performed on thin sheet blanks using a pinless tool; the rotational and welding speeds were kept constant during process. The dynamic tests were carried out, with a punch speed of 4500 mm/s, at different punch stroke values until failure of the friction stir welded sample. It was seen that failure occurs along the welding line at a dome height about 11% higher than that at the onset of necking. Fractographic analysis shows that deformation is localized in the fracture zone. The results were compared with those obtained on friction stir welded blanks deformed under quasi-static condition in order to evaluate the influence of the loading rate on the weld deformation and fracture mechanisms. It was shown that joints deformed under dynamic loading condition are characterized by a dome height at the onset of necking significantly higher than the one measured under quasi-static condition.