Microstructure improvement in weld metal using ultrasonic vibrations

The use of power ultrasonic vibration to refine the microstructure of weld materials was analyzed. The materials used were 304 stainless steel plates with 12 mm thickness and φ 3.2 mm commercial 316L stainless electrodes. The weld specimens were sectioned, polished, and electrolytic etched with 5% oxalic acid to reveal the microstructures. Grain growth was initiated from the fusion boundary and proceeded towards the weld centerline during solidification process that extended it without altering the crystallographic orientation. The direction of the ultrasonic vibration was found out to be perpendicular to the welding specimen during welding solidification. Results show that the weldment with equiaxed grains have improved the mechanical properties and hot tearing susceptibility.