关键词: 过冷, 共晶凝固, 再辉, 形核与长大, 快速凝固

Abstract: Large undercoolings up to 395K(0.28TE)have been obtained for Ni-32.5% Sn eutectic alloy by superheating the alloy melt which is 15g in weight to 108-976K above its eutectic temperature and consequently destroying a considerable number of heterogeneous nuclei within it. The recalescence phenomenon, its dependence on undercooling and crystal nucleation and growth, as well as its relationship to solidification structures have been studied. The crystallization fraction during recalescence is also calculated. It is found that the degree of recalescence increases with undercooling when the latter is below a certain critical value ATc, but it decreases as undercooling increases above ATc (in the specific case of the present paper, △Tc = 245K, i. e. 0.17TE).The greater the degree of recalescence, the larger the proportion of anomalous eutectic in the solidified structures. If the degree of recalescence is quite small, it is impossible for the anomalous eutectic to become the only solidification structure, and a certain a-mount of lamellar eutectic inevitably forms even at undercoolings as large as 376K.

Key words: undercooling, eutectic solidification, recalescence, nucle-ation and growth, rapid solidification.