Distribution of tensile property and microstructure in friction stir weld of 6063 aluminum

Abstract

Dominant microstructural factors governing the global tensile properties of a friction-stir-welded joint of 6063 aluminum were examined by estimating distribution of local tensile properties corresponding to local microstructure and hardness. Yield and ultimate tensile strengths of the as-welded weld were significantly lower than those of the base material. Postweld aging and postweld solution heattreatment and aging (SHTA) restored the strengths of the weld to the levels of the base material. Elongation was found to increase with increasing strength. Hardness tests showed that the as-welded weld was soft around the weld center and that the aged weld and the SHTA weld had relatively homogeneous distributions of high hardness. Hardness profiles of the welds were explained by precipitate distributions and precipitation sequences during the postweld heat treatments. The strengths of the welds were related to each minimum hardness value. In a weld having a heterogeneous hardness profile, the fracture occurred in the region with minimum hardness. When a weld had a homogeneous hardness profile, its fracture site depended on both crystallographic-orientation distribution of the matrix grains and strain tensor of the imposed deformation, i.e., it fractured in the region with a minimum average Taylor factor.

Tensile properties and fracture locations of friction-stir-welded joints of 2017-T351 aluminum alloy

“…A softened region has been formed in the joints of 2017-T351 aluminum alloy due to the effect of friction heat as occurred in the joints of other heat-treatable aluminum alloys [7,[21][22][23]. The tensile properties and fracture locations of the joints are, to a large extent, dependent on the welding defects and hardness distributions of the joints, and which, in turn, on the welding parameters [6,11,14].…”

“…Therefore, the FSW process can be used to weld heat-treatable aluminum alloys in order to obtain high-quality joints [1][2][3][4]. However, many studies on the microstructural characteristics and mechanical properties of the friction-stir-welded joints have indicated that FSW gives rise to softening in the joints of the heat-treatable aluminum alloys such as 2014-T651 [5], 2024-T3 [6,7], 2024-T351 [8,9], 2024-T6 [10,11], 2195-T8 [12,13], 6061-T5 [14,15], 6061-T6 [8,[16][17][18], 6063-T5 [19][20][21], 6082-T5 [22], 7075-T651 [23] and 7475-T76 [7] because of the dissolution or growth of strengthening pre-cipitates during the welding thermal cycle, thus resulting in the degradation of the mechanical properties of the joints. Hence, it is important to study the effects of welding process parameters on the mechanical properties of the joints and determine the optimum welding parameters so as to obtain high-quality friction-stir-welded joints.…”

Effect of Dynamically Recrystallized Grain Size on the Tensile Properties and Vibration Fracture Resistance of Friction Stirred 5052 Alloy

“…However the stir zone experienced dynamic recrystallization during FSP. Some previous studies [13][14][15] showed that the as-stirred specimens contained grains of high dislocation density. If the dislocation density of the grains in the interior of a material affects the slope value, the effect of dynamic recrystallization on the k y value needs to be examined.…”

“…Some other studies 15,18) have shown that dynamic recrystallization which occurs during FSP often leaves some grains with a high density of dislocations in the stir zone. This result suggests …”

Weibull Statistics for Evaluating Failure Behaviors and Joining Reliability of Friction Stir Spot Welded 5052 Aluminum Alloy

“…2,3) Recently, a new solid-state joining technology of the friction stir spot welding (FSSW), which is a derivative process of the friction stir welding (FSW), 4) has been developed as a widespread technique and successfully applied for producing lap-joints of aluminum alloys. [5][6][7] Compared with the traditional RSW process, FSSW can avoid severe heating and cooling cycles induced during welding process. Furthermore, the heat affected zone (HAZ) and residual stresses associated with the welds are relatively small.…”