Static shear strength and fatigue life of refill friction stir spot welded AA 6061-T6 sheets

Abstract

This study was aimed at evaluating the static shear strength and fatigue properties of the newly developed refilled friction stir spot welded AA 6061-T6 joints. The keyhole, the process disadvantage of conventional friction stir spot welding, was refilled successfully, using an additional filler plate, with specially designed tools. Two different tool profiles, namely, convex and concave, were used for the refilling process. Sound and defect free joints were obtained by the refilling process. Joints refilled with convex tools showed better static shear strength than those with the concave ones. The variation of microhardness in different regions of the weld was analysed. Fatigue tests were conducted on the lap shear specimens at a stress ratio of R50?1. The optical micrographs of the welds after fatigue failure in both the conventional and refilled processes were examined to study the fatigue crack propagation and failure modes.

Dissimilar Al/steel friction stir spot welding: To penetrate into the lower steel sheet or not?

“…Friction stir spot welding (FSSW) is a relatively new welding technology which has been used in recent years for joining various materials. [1][2][3][4][5] This welding process produces lower heat input than the fusion welding processes such as resistance spot welding and subsequently reduces the formation of intermetallic compounds (IMCs) by avoiding liquid phase reactions. 6 During FSSW, a rotating tool is inserted into two overlapping sheets to a predetermined depth.…”

Influence of SiC Nanoparticle Reinforcement on FSS Welded 6061-T6 Aluminum Alloy

“…But the sample with 29% SiC yielded the maximum hardness despite of its larger grain size [30]. The hardness was found to be gradually decreasing through TMAZ, HAZ and the hardness profile resembles the shape of "W" [19].…”

“…It is worth noting the presence of large pores on the fracture planes in SiC-free samples. In addition, with the fracture surfaces in the same direction, the stretched-out dimples can cause the shear fracture as published in [19].…”

“…Lee et al [17] reported that the pin angle of 5°, dwell time of about 4.5-5.5 seconds, rotational speed of 1000-1200 are optimum FSSW condition for expected defect-free FSSW on AA6061. Venukumar et al [18][19][20] studied the effect of different methods of FSSW on aluminum alloy 6061-T6. They attempted a walking FSSW method and suggested that welds obtained at the tool rotational speed of 900 rpm have better static shear strength when compared to the conventional FSSW.…”

Analysis of the effect of structural defects on the fatigue strength of RFSSW joints using C‐scan scanning acoustic microscopy and SEM

“…This technique makes it possible to avoid the formation of a thick intermetallic layer at the interface. Comparison of the fatigue behaviour in Mg/Mg similar and Mg/steel dissimilar RFSSW welds was a subject of the investigations of Shen et al The previous research reported by many authors proved that RFSSW has many advantages for the fabrication of joints in aluminium alloy sheets. The microstructure and mechanical properties of 7075‐T6 aluminium alloy joints joined by RFSSW were investigated by Shen et al They found that the main feature affecting the mechanical properties of the joint is the character of the connecting qualities between the stir zone (SZ) and thermomechanically affected zone (TMAZ).…”