Mechanical Properties of 6013-T6 Aluminium Alloy Friction Stir Welded Plate

Abstract

Aluminium alloys are widely used on aircraft structures especially on the fuselage and wing fairings. During the joining of these structures, the traditional technique riveting is used. But riveting increases the structural weight of the aircraft and rivet holes form stress concentration for the fatigue cracks. An alternative joining technique is welding. In traditional welding techniques metal is heated till the melting point for this reason the mechanical behavior of the material deteriorates. And also the weldability of high strength materials is low. In recent years Friction Stir Welding (FSW) has been used as an alternative joining technique. In this study T6 heat treatment is applied to Aluminium 6013 sheet and this sheet joined by using FSW technique. Tensile specimens were machined from the welded plate in the dimension of A0 = 12.5 mm, l0 = 200 mm and tensile tests were performed. Vickers microhardness values were taken at 1 mm increments from base metal to base metal across the weld, on the weld cross-sections. The intermetallic particles and the grain structure of the welded sheet were examined via optical and scanning electron microscopy.

Review Paper: Production and Microstructural Phenomena Affecting Friction Stir Welding Mechanical Behaviour and Applications.

“…The principal prospective application of FSW in aerospace is in the manufacture of integral fuselage structure and wing fairings. This entails butt-joining of rolled sheets and T-joining of stringers with skin sheets and clips [8,9,32]. This is proposed to eliminate the problems of excess weight, high cost, widespread fatigue damage and energy consumption associated with the traditional fastening method of riveting, while also optimizing production time, corrosion resistance, damage resistance, reliability, maintainability, service life and safety [7-9,32-35,].…”

“…Alloy 6013 is an Al-Mg-Si-Cu alloy and a medium strength aerospace alloy that provides high formability, machinability, improved corrosion resistance, lower density, and low sensitivity to high temperature. It has yield strengths 12% higher than Alclad 2024-T3, virtual immunity to exfoliation and stress corrosion cracking, and lower price [9,32,47]. It is weldable by gas tungsten arcwelding (GTA), metal gas arc-welding (MGA), and resistance welding.…”

“…low strain-to-failure) when compared to unwelded parent materials [70]. Under static loading, failure has mostly been reported to have occurred in the HAZ [1][2][3][4][5][6][7][8][9][10]16,17,21,71,72]. The direction of tool rotation, which accounts for asymmetry in heat transfer and material flow, has also led to differences in the mechanical properties on the advancing and retreating sides of the FS weld [10].…”

“…Heat treatment causes the precipitation of the strengthening Mg2Si and Mg-Si-Cu-Al phases [1,97]. Naturally, aged FSW samples revealed a shallow 'W" hardness curve across the weld, as shown in Figure 21 [1,9,72]. Hardness reduction in the nugget, slightly less than 26% of the base material, was recorded by Juricic et al [87], which implied that strength and ductility would be lower than that in the base material [1,9,72].…”

“…Naturally, aged FSW samples revealed a shallow 'W" hardness curve across the weld, as shown in Figure 21 [1,9,72]. Hardness reduction in the nugget, slightly less than 26% of the base material, was recorded by Juricic et al [87], which implied that strength and ductility would be lower than that in the base material [1,9,72]. Welding in the T6 condition and subsequent PWHT to the T6 condition again resulted in a minimum hardness of 104 HV in the very narrow low hardness region in the HAZ.…”