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ABSTRACT
Friction stir processing (FSP) is an effective technique in microstructural refinement. It is expected to make a great change in the manufacturing industries. However, the weak region of thermo-mechanically affected zone (TMAZ) limits the practical application of FSP. Hence, double-sided FSP (DFSP) was proposed to eliminate such weak zone. In this work, 7050-T7451 alloy plates were processed by the single-sided FSP (SFSP) and DFSP (two parameters: DFSP-0O-50D and DFSP-30O-35D). The DFSP-30O-35D parameters can ensure the overlapping of the former and later stir pin, which prepared the refined and homogeneous microstructure without TMAZ, and result in a significant enhancement of mechanical properties. In the former SZ, the main precipitates are Al2CuMg and η (MgZn2) phase; in the later SZ, the main precipitates are η′ phase with smaller size and higher quantity. It caused a higher microhardness of the later SZ than the former ones.