PART II - Papers - Rapid Quenching of Reactive and Refractory Alloys from the Liquid State

A Hew melting technique has hem adapted to the rapid quenching of- alloys from the liquid state. The inelting method has no limitations on the alloys investigated for there is no reaction with crucible materials and the most refractory materials are easily melted. The vate of heating is so rapid that alloys which have a high vapor pressure constituent can be melted with a minimal loss in material. Several new superconductovs have been discoveved by vapid quenching of lolten alloys. THE rapid quenching of alloys from the liquid state has led to the discovery of many new metastable phases. The methods initially used were limited to alloys which did not react with crucible materials.1,2 There was also the unmentioned limitation in tem- perature. Alloys with melting points much greater than 2000°C could not be melted in the rapid-quench apparatus. Recently, there have been successful attempts to rapidly quench reactive alloys by Moss et at. and Matthias Moss et al. injected powdered material (325 mesh) into a high-temperature plasma and the high-velocity molten droplets impinged on a cooled copper plate. The technique innovated by Matthias was to melt the alloy in an arc furnace and splatter it against a copper plate by means of a high-velocity gas jet aimed at the melt. I) FAST COOLING APPARATUS The creation of a metastable phase in a given alloy system by rapid cooling from the melt is contingent on the quenching rate. Some alloys require very slow rates while other alloys require the ultimate in quenching rate. At the present time, the vertical-gun technique of Duwez and willens' has demonstrated, in practice, the highest quenching rates and thus the best