RAPIDLY QUENCHED METALS IBD

Sinopse

Professor Pol Duwez of the California Institute of Technology, Pasadena, USA, developed a method in 1960 to solidify metallic melts at cooling rates exceeding about 105 K/sec. It was shown that under these non-equilibrium conditions it was possible to obtain supersaturated solid solutions, metastable crystalline inter¡ mediate phases and even amorphous phases under appropriate quench¡ ing conditions and for suitable alloy compositions. Subsequently, several other techniques have also been developed to achieve these non-equilibrium effects. A common feature of all these rapid quench¡ ing techniques ~ow collectively referred to as splat quenching, liquid quenching, melt quenching or liquisoi quenching) is that quenching is carried out from the liquid state at very high cooling rates. However, the shape and size of the quenched product may be different depending on the technique employed. The method of melt spinning- in which a continuous stream of liquid jet is impinged against a conducting wheel rotating at a high speed - has become the most popular since long and continuous ribbons of uniform cross section can be obtained. Although started only about 20 years ago, the rapid quenching technique has come to be established as a standard method to produce metastable effects. The activity in this area is now world-wide as evidenced by the organization of three international conferences devoted exclusively to this topic. The first one was held in Brela, Yugoslavia (1970), the second in Massachusetts, Cambridge, USA (1975) and the third at Sussex, UK (1978).