ABRUPT DISCONTINUOUS RELATIONSHIPS BETWEEN SUPERCOOLING AND MELT OVERHEATING

The dependence of the degree of supercooling (Delta T-) of melts prece ding the onset of solidification on the level of melt overheating (Del ta T+)above the equilibrium liquidus or melting temperature, is invest igated on Sn and SnPb. We demonstrate the dependence of Delta T- on De lta T+ can be either abrupt or continuous, depending on the length of holding time. In particular, the dependence is bounded by two disconti nuous limits, and the known continuous linear relationship between Del ta T- and Delta T+ is only a special possibility. Our observations can be tentatively linked to the transient structural evolution of melts, and are probably general, occurring also for element Bi and SnSb. Our results may have important consequences for any thermal modeling of e lectronics manufacturing involving soldering operations. (C) 1997 Amer ican Institute of Physics.