Phase selection and microstructure evolution of undercooled Fe-Cu peritectic alloy

<正> Fe-Cu pentectic alloy was melted and superheated within a special boronsilicate glass, then under-cooled in argon atmosphere. Undercoolings up to 277 K were attained and the hypercooling limit of the alloy was de termined to be 395 K. The microstructurcs of the alloy were characterized by a supersaturated αFe matrix plus a small amount of Cu phase distributed as tiny particles δFe phase was the actual nucleating phase in the small undercooling regime below 125 K. But γFe phase might be able to nucleate directly from the liquid alloy at still larger undercool ings. Solute trapping effect was found in this alloy system. It was also found that the recalescence temperature de creased and the recalescence rale increased with undercooling. A maximum dendrite growth velocity of 50 m·s was detected experimentally, which corresponded more probably to γFe dendrite growth. Theoretical calculations based on the LKT/BCT dendritic growth model indicate that for δFe phase there is a transition from solute diffus