Texture Development and Material Flow Behavior During Refill Friction Stir Spot Welding of AlMgSc

Abstract

The microstructural evolution during refill friction stir spot welding of an AlMgSc alloy was studied. The primary texture that developed in all regions, with the exception of the weld center, was determined to be h110i fibers and interpreted as a simple shear texture with the h110i direction aligned with the shear direction. The material flow is mainly driven by two components: the simple shear acting on the horizontal plane causing an inward-directed spiral flow and the extrusion acting on the vertical plane causing an upward-directed or downward-directed flow. Under such a complex material flow, the weld center, which is subjected to minimal local strain, is the least recrystallized. In addition to the geometric effects of strain and grain subdivision, thermally activated high-angle grain boundary migration, particularly continuous dynamic recrystallization, drives the formation of refined grains in the stirred zone.

Experimental and Numerical Analysis of Refill Friction Stir Spot Welding of Thin AA7075-T6 Sheets

“…The material adjacent to the shoulder inner periphery, underneath the shoulder, and adjacent to the shoulder outer periphery is further squeezed towards into the reservoir, see points P5, P15, P25, P6, P16, P26, P7, P17, and P27. This material movement is influenced by the shoulder outer wall [ 34 ].…”

Effect of Sleeve Plunge Depth on Interface/Mechanical Characteristics in Refill Friction Stir Spot Welded Joint

“…The joint-line remnant is interpreted as the remnant oxide film originating from the faying surface [18]. It is considered to be a region which can reflect the metallurgical bonding between two sheets, and can be divided into two parts: [14].…”

“…4). Shen et al [18] have reported that the initial interface will become deformed during penetration stage even when the plunge depth is less than upper sheet thickness. However, the weak material flow near the interface owing to the fact that the sleeve has not reached the lower plate cannot form evident hook at SZ margin at sleeve depth of 1.75 mm.…”

Refill Friction Stir Spot Welding of Similar and Dissimilar Alloys: A Review

“…Figure 2 shows the microstructure in cross section of 2024 aluminum alloy joint, which is similar to that of 6061 and AlMgSc aluminum alloys and AZ31 magnesium alloy. Based on grain structure, the welded area is characterized as two zones: stir zone (SZ) and thermomechanically affected zone (TMAZ), which is similar to FSW welded area [7][8][9][10]. The TMAZ is often characterized by grains Available online at http://link.sprin ger.com/journ al/40195 .…”

“…Partially recrystallized grains are often found in the center of the SZ due to the relatively low local shear strain. The bottom border of the SZ is characterized by fibrous structures and textural structures [10,11].…”