A Pathway to Grain Structure Control of Gas Tungsten Arc Welded Duplex Stainless Steel Through Ultrasonic Vibration

In-depth understanding of microstructural modification and grain refinement is required to manufacture high quality products by gas tungsten arc welding. Here, we report the governing role of ultrasonic vibration in the improvement of microstructure and mechanical properties of the as-welded duplex stainless steel. We show that the columnar-to-equiaxed transition was promoted and fine equiaxed grains with no preferred crystallographic texture could be achieved involved in welding. Detailed microstructural features coupled with acoustic field simulation were carried out to reveal the mechanisms of grain refinement. This was attributed to the production of many initial nuclei or crystallites which resulted from the acoustic cavitation in the ultrasonic vibration of weld pool. Consequently, the formation of this microstructure led to a significantly increased tensile strength and maintained acceptable ductility. These findings offer a new perspective on control of grain structure in the as-welded condition by extending ultrasonic vibration to duplex stainless steel welding.