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Abstract
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In the present study, the effect of tool pin profile on microstructure and mechanical properties of friction
stir welded pure copper joints were investigated. Two different tools with threaded cylindrical and
square pin profiles were used to fabricate the joints at constant rotation rate of 600 rpm and traverse
speed of 75 mm/min. Four K-type thermocouples were used to record the temperature histories of samples
during FSW. Microstructure features of the joints were characterized by optical microscopy and the
obtained images were quantified using image analysis technique. Tension test and Vickers hardness measurements
were also performed to characterize the mechanical properties of the joints. Obtained results
showed that sample welded using square pin profile had finer recrystallized grain structure and higher
mechanical properties relative to sample welded by threaded cylindrical one. These results were attributed
to higher eccentricity of the square pin profile and its pulsation effect which led to higher degree of
plastic deformation and higher heat input into the joints.
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