Search

In the rotating water layer atomization process, a thin stream of molten metal impinges on a rapidly spinning disk that has a roughened surface cooled by a continuous water layer. The rapid rotation of the disk disperses the water radially outward, producing a water mist in the collecting chamber, which effectively cools the metal droplets formed upon impact on the disk and thrown off tangentially. The particles obtained by this method are randomly elongated droplets, and their internal microstructure is typical of rapidly solidified material, albeit with a few peculiarities. On average, the particles are coarser but are highly convoluted, and hence the material has a microstructural refinement comparable to the finer portion of helium-atomized powders, which is of crucial importance when preparing highly alloyed, impossible-to-cast material. Mechanical testing was performed at room temperature and at 200°C and 300°C; improved mechanical properties were obtained at moderately elevated temperatures.

Aggregates of small metal droplets of mercury, bismuth, gallium, and lead have been supercooled to a much greater extent than have large continuous liquid masses of the same metals. These results are interpreted on the basis that breaking a large liquid mass into small droplets isolates inclusions that usually catalyze nucleation in a small fraction of the droplets so that most must nucleate homogeneously.

Iron-in-slag emulsions are shown to be created by the attachment of large silicate or phosphate anions onto the surfaces of metal droplets, thus combining the droplet within the slag structure. The most significant factors favoring emulsion stabilization are: a high concentration of anion chain forming oxides such as Si02, Al2Os, and especially P205; and a high concentration of iron oxides. The absorption of iron ions (from iron oxides) is shown to neutralize the anion droplet pairs to form highly stable iron-in-slag emulsions.