Effect of Post Weld Heat Treatment on Tensile Behavior of Al 2024-T8 Friction Stir Welded at Different Rotational Speed

In friction stir welding (FSW) as a solid state joining method, heat is generated due to the friction and plastic deformation of the work-piece resulting from high rotation along with plunging of the tool. Consequently, although joint strength of FSW parts influenced by rotational speed as an essential processing factor, other factors not dependent on processing such as post-welding treatments influenced on the strengths of joints by microstructural alteration of welding zones. Considering, in this study, the effects of rotational speed ranging from 700 to 1100 rpm, as a processing parameter, on the microstructure and tensile properties of FSW 2024-T8 Al-Cu alloy were investigated. In order to examine the effect of post-welding treatment, T6 tempering as a routine aging condition was applied on 2024-T8 joints. The results show increasing rotational speed leads to more strength but less elongation of joint, in which the superior strength was obtained at 1100 rpm (72.3% of base metal). Polarized micrographs show more abnormal grain growth with respect of increasing rotational speed which clarify the maximum strength of samples at 1100 rpm. Contrary to strength, all the joints show significant loss in elongation which maximum elongation reached to only 13.8% of base metal at 700 rpm. Although T6 post weld heat treatment had unfavorable effects on the strength of the joints, but 20% enhancement in elongation was achieved at 1100 rpm.

کلیدواژه ها:

Friction stir welding ، Al 2024-T8 ، Tensile properties ، Microstructure ، Post-weld heat treatment.