Evaluation of microstructure and mechanical properties of friction stir welded copper / 316L stainless steel dissimilar metals

In the present research, friction stir welding (FSW) process was used for butt joining of pure copper plate to 316L stainless steel plate. Mechanical properties and microstructural characteristics of the joint were evaluated by microhardness and tensile tests as well as optical and scanning electron microscope (SEM). It was found that microstructure of the weld nugget (WN) has fine grains whereas the elongated grains are located in the thermo mechanically affected zone (TMAZ) into 316L stainless steel. Also, coarse grains are observed in the heat affected zone (HAZ) into pure copper. The microhardness values of the WN are much higher than the base metals. The HAZ zone shows minimum hardness values. The butt joint has 85% weld efficiency compared to the copper base meal.