Solidification behavior of undercooled Cu-20
wt%Pb
hypomonotectic alloy was studied by employing the complex method of molten glass denucleating combined with thermal cycling so as to obtain
high undercooling up to 208 K in Cu-20wt%Pb hypomonotectic alloy melt.The results indicate that the undercooling alloy melting primary phase is α(Cu),and that twice
recalescence occurred in Cu-20wt%Pb hypomonotectic alloy melts in the range of 0K to 146 K,and the second recalescence was smaller than the first recalescence,whereas only once
recalesence was observed for those melts with undercoolings in the range of 183 K to 208 K.When the undercooling was less than 98 K,the
microstructures were composed of coarse dendrites and interdendritic lead phase. With the
Undercooling increasing up to the range of 116 K to 146 K, the morphology of dendrites grains in the Cu-20wt%Pb hypomonotectic alloy became unapparent,the microstructures were composed of dense α(Cu) substrate and refined Pb grains; When the undercooling exceeded 183 K,the microstructures were similar with those of the alloy at moderate undercoolings,whereas Pb phase became much smaller and distributed more even.Hot-cracks existed in the alloy when the undercooling exceeding 133 K.