Effects of post-weld heat treatment on the microstructural evolution and mechanical properties of dissimilar friction stir welded AA6061+SiCp/AA6061-O joint

Abstract

A research on the microstructure and mechanical properties of the dissimilar joint was carried out so as to understand the effects of post-weld heat treatment (PWHT) on microstructural evolution, microhardness, tensile and flexural properties of the dissimilar friction stir welded (FSWed) joint. The results showed that there is a sufficient and rather complicated material mixing in the nugget zone (NZ). After PWHT, the grains in the joint area except for the NZ demonstrated a grain refinement with more homogeneous and equiaxed grains. Fine and clustered SiC particles in the NZ are confirmed by scanning electron microscope (SEM). In addition, the microhardness values of nugget zones both in as-welded and PWHT condition exhibited a higher Vickers compared to that of AA6061-O. Furthermore, a mean tensile strength of 183.30 MPa that demonstrates a 52.22% increase in tensile strength is also observed in the transverse tensile tests subsequent to PWHT. Considering the three-point bending test results, it is explicit that an increase of 121.96% in the bending extension is obtained as there is no significant increase in maximum bending force after the PWHT.

Microstructural and Mechanical Behaviour Evaluation of Mg-Al-Zn Alloy Friction Stir Welded Joint

“…The tensile samples failed at HAZ of the advancing side in case of the weld and BM specimens failed almost at the centre, see Figures 8(c) and 8(a). Similar observations for the FSW joint were reported by Oztoprak et al [53] that the as-welded FSW joint was fractured near or at the interface HAZ (AS). Figure 9 represents the strain-stress curves of BM, as-welded, and PWHT weld joints.…”

Microstructure and Mechanical Properties of Friction Stir Welded AA6061/AA6061 + 40 vol% SiC Plates

“…It is therefore apparent that further experiments are required to establish optimum combinations of tools and welding parameters for FSW of Al-base MMCs with a very high particle content to Al alloys. An alternative The average ultimate tensile strength (UTS) for the tested specimens is 166 MPa, which is at least 18% higher than the UTS in friction stir welded AA6061/Al + 20 wt% Mg 2 Si plates [11] and almost 40% higher than that reported for as-welded AA6061-O/AA6061 + 20 vol% SiC plates [12], though it is lower than the average strength, 208 MPa, measured in AA6061-T6/AA6061 + 20 vol% SiC plates [13]. Considering that the strength of the welded plate is controlled by the strength of the softest HAZ region on the AA6061 side, it is expected that the overall performance of the AA6061/AA6061 + 40 vol% SiC welds can be improved by increasing the strength of the HAZ.…”

“…It is therefore apparent that further experiments are required to establish optimum combinations of tools and welding parameters for FSW of Al-base MMCs with a very high particle content to Al alloys. An alternative approach to improve the strength of friction stir welded Al/Al MMC plates is to apply post-weld heat treatments [12,19], though it is obvious that this approach can only be effective for age-hardenable alloys.…”

“…Reinforcement particles in the MMC were chosen to be SiC and the AA6061 alloy was both the MMC matrix and the monolithic material, to which the MMC plate was friction stir welded. FSW was conducted in the present experiment on 8-mm-thick plates which were significantly thicker than other friction stir welded Al/Al MMC plates described in several previous publications [6][7][8][9][10][11][12]. The microstructure of the as-received and friction stir welded plates is characterized in this work using optical microscopy and scanning electron microscopy (SEM).…”

“…FSW was successfully applied for joining of commercial Al alloys and Al-base MMCs containing 15 to 25 vol% ceramic particles [7][8][9][10][11][12][13][14]. To the best of our knowledge, there are no publications describing FSW of Al/Al MMCs with a much higher particle content.…”