RAPID DECOMPRESSION OF SEEDED MELTS FOR MATERIALS PROCESSING

A novel processing approach and experimental design to achieve as-cast bulk amorphous materials are investigated. By sudden decompression of a melt that is seeded with a volatile liquid, the dispersed "foaming" liquid vaporizes, taking its latent heat of vaporization from the melt, thereby homogeneously cooling the melt. Due to a high decompression rate, a sufficient cooling rate may be produced to yield an amorphous solid foam. The resulting "foam glass" is expected to be an open solid bulk structure that may possess glass properties and low density. These foam glass materials should be free of structural defects, and may have many potential applications. The ultimate goal for this form glass processing is to produce bulk amorphous metallic solids. This approach differs from other processes used in the production of metals with a porous structure. A description of the approach, the processing design and techniques, as well as some evaluation of foam processing with the organic p-terphenyl as a sample material are presented. Foam (p-terphenyl) is an open, porous, and yet interconnected structure, and can be made with a density as low as 12% of the original density of p-terphenyl. Extension of this principle to foam metallic glass processing is anticipated. Design of a more sophisticated apparatus for metal processing, currently in progress, is discussed. © 1995 American Institute of Physics.