PRODUCTION OF FINE METAL POWDERS BY ULTRASONIC STANDING-WAVE ATOMIZATION

Ultrasonic standing wave atomization (USWA) is a process capable of pr oducing spherical metal powders with minimum mass median diameters of <15 mu m. Atomization is achieved by acoustic forces acting upon a jet of molten metal which is guided into the central pressure node of a s tanding wave field. Cooling rates of at least 2 . 10(5)K/s have been o bserved. The influence of different operating parameters on mass media n diameter is evaluated. Parameters which were varied are ambient gas pressure, vibration amplitude of the transducers, metal feed rate, and energy concentration by usage of different focal radii of the transdu cers. The powders are analyzed with a laser diffraction particle sizer , and the constitution of the powders illustrated by scanning electron microscopy. Atomized melts include Sn, Gu, and Mg.