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Abstract
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This research was carried out to predict the mechanical properties of friction stir welded pure copper
joints. Response surface methodology based on a central composite rotatable design with three parameters,
five levels, and 20 runs, was used to conduct the experiments and to develop the mathematical
regression model by using of Design-Expert software. The three welding parameters considered were
rotational speed, welding speed, and axial force. Analysis of variance was applied to validate the predicted
models. Microstructural characterization and fractography of joints were examined using optical
and scanning electron microscopes. Also, the effects of the welding parameters on mechanical properties
of friction stir welded joints were analyzed in detail. The results showed that the developed models were
reasonably accurate. The increase in welding parameters resulted in increasing of tensile strength of the
joints up to a maximum value. Elongation percent of the joints increased with increase of rotational speed
and axial force, but decreased by increasing of welding speed, continuously. In addition, hardness of the
joints decreased with increase of rotational speed and axial force, but increased by increasing of welding
speed. The joints welded at higher heat input conditions revealed more ductility fracture mode.
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