Abstract: Friction stir processing (FSP) were carried out to modify the mechanical properties of 7A60 aluminum alloy. The effect of friction stir processing parameters on the microstructure and mechanical properties of 7A60 aluminum alloy were investigated. The results showed that the uniform and fine equiaxed grains were formed due to dynamic recrystallization and the second phases were refined by severe plastic deformation with homogeneous distribution in the Al matrix. Meanwhile the content of η (MgZn2) phase decreased under the action of FSP heat, indicating the occurrence of the dissolution of η(MgZn2) phase into the Al matrix. Velocity ratio factor (ω/v) was a decisive impact factor of the mechanical performance of the nugget zone. With the increase of ω/v, the microhardness of the FSP-processed sample firstly increased and then decreased. The highest Vickers hardness was 120, which was 37.5% higher than the base metal, was obtained when ω/v reached 5, and the tensile strength increased to 449.9MPa. With the increase of ω/v, more heat produced by the stirring head led to significant grain coarsening and the dimples of the tensile specimens fractography become shallow, which in turn severely affected the tensile strength and plasticity of the material.

Key words: friction stiring processing (FSP); 7A60 aluminum alloy; microstructure; mechanical properties