Rapid solidification behavior and microstructure of highly undercooled Cu--Pb monotectic alloy melts
深过冷Cu-Pb偏晶合金的快速凝固行为和凝固组织

The solidification behavior and structural evolution of Cu--Pb monotetic alloy (Cu--25\%Pb, Cu--37.4\%Pb and Cu--40\%Pb, mass fraction) were investigated by means of combination of melted glass denucleation and cyclical superheating, and the relationships between undercooled microstructures and wear rate were studied. The results show that during the solidification of undercooled Cu--25\%Pb hypomonotectic melt, $\alpha$(Cu) nucleates first, whole solidification course follows the mode of the undercooled single--phase alloy melts, and the structures undergo the evolvement processes in which fine dendrites change into a kind of quasi--spherical grain with undercooling increasing. During the solidification of undercooled Cu--37.4\%Pb monotectic and Cu--40\%Pb hypermonotectic melt, $L_{2}$ liquid phase nucleates ahead of $\alpha$(Cu), and the monotectic microstructures and the hypermonotectic microstructures within undercooling range can be obtained, respectively. The wear rate of Cu--37.4\%Pb monotectic alloy reduces gradually with the increase of undercooling.