Investigation on the microstructures and mechanical properties of friction stir processed 2A14 aluminum alloy fabricated by different initial precipitation states

Six-millimeter-thick 2A14 Al alloy plates were friction stir processed (FSP) with different initial precipitation states of as-cast, homogenization, rolling, and T6. The results indicated that FSP can dramatically reduce the grain and particle size and promote the formation of fine recrystallized grains with random orientation in the stirred zone (SZ). No significant influences of the initial precipitation states of base metal (BM) on the grain size, grain boundary characteristic, texture component, and texture intensity of SZ were perceived. Rather, the initial precipitation states can evidently affect the morphology and distribution of precipitates and dislocations. The dominant C and A(1)* texture components developed in the SZ are correlated with the shear deformation and dynamic recrystallization. And the weakened texture intensity created in the SZ after FSP also signifies that discontinuous dynamic recrystallization might be involved. Compared with the corresponding BM, the SZ fabricated by the BM under as-cast and homogenized states was strengthened arising from the obvious refined grains, uniform dispersed particles, and elimination of casting defects caused by FSP, while the softening of SZ was observed for the BM under rolled and T6 states, which are mainly dependent on the reduction of dislocation density and dissolution/coarsening of fine precipitates during FSP.