Abstract
When considering the operational performance of weldments in the engineering projects, the most important issues to be considered are weld metal mechanical properties, integrity of the welded joint, and weldability��1�� . These issues are closely related to the microstructure of the weld metal. A significant amount of research has been carried out to alter the process variables and to use external devices to obtain microstructure control of the weldments. It has been reported that grain refined microstructure not only reduces cracking behavior of alloys including solidification cracking, cold cracking and reheat cracking, ��2 - 5�� but also improves the mechanical properties of the weld metal, such as toughness, ductility, strength, and fatigue life. ��6, 7�� Weld pool stirring, ��8�� arc oscillation, ��9, 10�� arc pulsation, ��11��, and magnetic arc oscillator ��12, 13�� have been applied to fusion welding to refine the microstructures. This article describes initial experimental results on the use of power ultrasonic vibration to refine the microstructure of weld metals.