Methods of ultrasound assisted welding

A method of ultrasound-assisted welding of solid metallic materials for eliminating hot tearing in order to make the solid metallic materials weldable, comprising the step of:

• forming a melt pool by melting a solid material using a heat source used for welding, wherein the melt pool consists a center and a solid-liquid interface defining an edge of the melt pool;
• making the melt pool to travel with the heat source, melting solid materials in front of the melt pool and solidifying melted material at back of the melt pool, forming recently solidified materials;
• placing an acoustic sonotrode of an ultrasonic vibration system adjacent to the edge of the melt pool on the recently solidified materials, wherein an end of the sonotrode in contact with the recently solidified materials is within millimeters from the center of the melt pool and wherein the end of the sonotrode in contact with the recently solidified materials has a curve surface;
• applying a compressive thrust load on the sonotrode;
• synchronizing the sonotrode and the heat source such that the sonotrode and the melt pool travel side-by-side at a fixed distance between the center of the melt pool and the end of the sonotrode;
• and
• applying high-intensity ultrasonic vibrations through the sonotrode to transmit the vibrations to the melt pool via materials under the sonotrode the sonotrode,
• wherein said high-intensity ultrasonic vibrations are used to reduce grain size and eliminate hot tearing in the recently solidified materials and a combined action of said high-intensity ultrasonic vibrations and said compressive thrust load condenses the recently solidified materials.