Microstructure and texture evolution of stationary shoulder friction stir welded Ti6Al4V alloy

Abstract

Microstructure evolution and texture evolution in the weld zones during stationary shoulder friction stir welding of Ti6Al4V alloy of 7 mm thickness have been investigated by optical microscopy and electron backscatter diffraction method. A unique method was developed to differentiate the heat affected zone (HAZ) and the thermomechanically affected zone (TMAZ). The weld zones are characterised by equiaxed structure in the base material (BM), bimodal structure in the HAZ, coarse lamellar structure in the TMAZ and fine lamellar structure in the stir zone (SZ). Prismatic texture {11 20}v0001w and {11 20}v10 10w were developed in the BM and the HAZ, the SZ is dominated by the simple shear texture component D1 (11 2)[111] and the TMAZ has intermediate shear texture D1.

Microstructure and properties of electrically assisted stationary shoulder friction stir welded Ti6Al4V

“…To improve the weldability and joint properties of FSW of titanium alloys, stationary shoulder FSW (SSFSW) was invented by TWI in 2004 to solve the problems of gradient temperature distribution, especially the surface overheating, along the thickness direction of the titanium joints due to its low thermal conductivity [19], and a relatively homogenous microstructure along the direction of plate thickness was reported by Russell et al and Wynne et al [20, 21] with excellent forming and good joint performance. Davies [22] and Jiang [23, 24] also observed the uniformed distributed microhardness along the plate thickness with varying welding parameters. SSFSW solves the problem of surface overheating, produces a much more uniform heat input imposed on the joint and improves the joint quality.…”

Material flow and viscous slips during stationary shoulder friction stir welding of Ti6Al4V

“…Therefore, stationary shoulder stir friction welding (SSFSW) was developed by The Welding Institute, UK, to eliminate the problem of uneven temperature distribution along the thickness direction. And it is urgent to quantify the thermomechanical conditions such as temperature and material flow to optimise welding parameters for SSFSW process [11].…”

Art of friction stir welding to produce weld joint without rotation of shoulder with narrow heat-affected zone and high corrosion resistance

“…The non-rotating shoulder slides along the weld line without rotation during the welding [6]. Initially, the tool with a non-rotating shoulder was developed for FSW of Ti alloys and later implemented for other metal systems such as aluminium [7]. Non-rotating shoulder tool has been reported to produce a defect-free weld joint of AA7075 at various speed parameters [8].…”

“…The material penetration occurs through the gap between rotating sub-shoulder and non-rotating shoulder. Previous studies [5][6][7][8][9][10][11][12][13] primarily reported the metallurgical and mechanical properties of the NRS-FSW joints. However, the corrosion behaviour of the NRSFSW joint of aluminium alloys has not been investigated to the best knowledge of the authors.…”