The Effect of Friction Stir Processing on Microstructure and Mechanical Properties of Al6061-T6 Aluminium Alloy

In this research, the influence of friction stir processing (FSP), on structural and mechanical properties of Al6061-T6 was investigated. Friction stir processing with tool rotational rate (ω) of 630, 800 and 1000rpm and traveling speed (v) of 50,100,160 and 200mm/min was employed on 13mm thick Al6061-T6. Results indicated that FSP decreases grain size from 78µm to 6µm because of the dynamic recrystallization. The finest grain size was obtained at the rotational rate of 630 rpm and traveling speed of 100 mm/min. Results have recommended that when the ratio of ω/v was less than 5(rpm/mm.min-1), due to inadequate heat input, microscopic voids were produced in nugget zone (NZ). Microhardness and tensile strength in the stir zone decreased, but elongation raised compared to those for the base metal. This is due to the loss of hardening precipitates during FSP.With increasing the tool travelling speed, grain size in nugget NZ and mechanical properties were improved. The best mechanical properties at NZ have been obtained at ω=630 rpm and v=100 mm/min due to the finest grain size.