Abstract
The effect of tool rotational and welding speeds on the microstructure and mechanical properties of friction stir welded AA5086-O was studied. Optical metallography and scanning and transmission electron microscopy were used to characterize the microstructure of different zones of welds. The relationship between residual stress profiles and local mechanical properties of different weld zones was studied using X-ray diffraction (XRD) and Digital Image Correlation (DIC), respectively. A lower speed ratio (tool rotational speed/tool traverse speed – ω/v) reduced the grain size and increased hardness and tensile strength in the stir zone (SZ). The longitudinal and transversal residual stress profiles in the welds show a good correlation between the ω/v) ratio (welding heat input) and local mechanical properties of different zones of FSWed joints. The weld produced with the highest heat input showed the lowest residual stress. Also, the residual stresses of different weld zones increased with their yield stress.

Key words
friction-stir welding, AA5086 aluminum alloys, microstructures, mechanical properties, residual stress

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