INVITED: Effect of Tool Rotational Speed on Microstructure and Microhardness of Friction Stir Welded 321 stainless steel
By Pradeep Johnson (Hindusthan College of Engineering and Technology), Murugan Nadarajan (PSG College of Technology)

In this study, 3 mm-thick 321 stainless steel plates was butt welded by friction stir welding at a welding speed of 45 mm/min and tool rotational speed of 500 and 700 rpm. Metallographic examinations, and tensile and microhardness tests were utilized to investigate the microstructure and mechanical properties of the joint. In the SZ zone of the 321 SS welded plates, a refined grain structure with some features of recrystallization was evident. A thermomechanically affected zone was characterized. The heat-affected zone in the stainless steel side showed partially and fully refined microstructures. The recrystallization in the 321 stainless steel enhanced the hardness of the weld area and therefore, improved the tensile properties of the joint. The effect of the tool rotational speed on microhardness is also reported in this paper.