Effect of SiC nanoparticles on the microstructure and texture of friction stir welded AA2024/AA6061

Abstract

In the present study, the effect of SiC nanoparticles on the microstructure and texture evolution of friction stir welded AA2024/AA6061 dissimilar joint investigated. The results showed that the SiC nanoparticles homogeneously dispersed in the aluminum matrix. The Al/SiC interfaces had a good quality of bonding between particles and matrix. It was found that the new recrystallized aluminum grains tend to nucleate and grow on the 11¯1 crystal plane of SiC nanoparticle (1¯1¯1Al facet on 11¯1SiC surface). The average grain size in the stirred zone (SZ) decreased to 7.4 μm owing to the grain refinement through the occurrence of both dynamic and static recrystallization. Most grains in the center of the stirred zone grown due to the occurrence of continuous grain growth (CGG) mechanism after the stirring. Moreover, the incorporation of SiC nanoparticles led to a reduction of 26% in the mean grain size of the SZ. The average size of the precipitate particles in the stirred zone was much smaller than the thermo-mechanically affected zone (TMAZ) owing to the dissolution of precipitates during stirring and reprecipitation during cooling. In addition, the grain size of the stirred zone on the advancing side was lower than the retreating side (2.6 μm vs. 9.7 μm). The results revealed a weaker texture after FSW compared to the initial samples. The SiC nanoparticles largely suppressed the rotation of the {001}〈100〉 oriented new grains through particle pinning effect. Unlike the advancing side, there was no recrystallization texture component on the retreating side.