Effect of ultrasonic vibrations in TIG welded AISI 321 stainless steel: microstructure and mechanical properties

In the present work, the effect of ultrasonic impacts on the TIG welding microstructure and mechanical properties of AISI321 stainless steel was investigated and the main effective mechanism was discussed. Metallographic results reveal that ultrasonic impacts induce mechanical shock in the weld metal and change the size and morphology of ferrite and austenitic dendrites that result in grain refining of weld metal compare to original TIG welding. Ultrasonic vibration of weld pool promotes the dendrite fragmentation as main mechanism of grain refining. Moreover, weld pool convection restricts equiaxed grain growth near fusion line region by carrying fragmented dendrites to weld center and main microstructure of near the fusion line is fully fine nondendritic equiaxed grains. Ultrasonic impacts considerably improve tensile properties and average hardness of weld metal by microstructural change of weld metal.