Achieving friction stir welded pure copper joints with nearly equal strength to the parent metal via additional rapid cooling

 Friction stir welded (FSW) pure copper joints with nearly equal strength to the parent metal were obtained at 400 rpm/50 mm min–1 via additional rapid cooling with flowing water. Significantly reduced heat input with a peak temperature of 130 °C and duration of 4 s above 100 °C in the thermal cycle was achieved in the heat-affected zone, resulting in the retainment of the original high dislocation density of the parent metal. This work provides an effective strategy to enhance the strength of FSW joints.

Research highlights
► Heat input was significantly reduced via rapid cooling during friction stir welding.
► The pure copper joints with nearly equal strength to parent metal were obtained.
► A very low peak temperature of 130 oC was observed in the heat-affected zone (HAZ).
► Original high dislocation density in the parent metal was retained in the HAZ.