深过冷Cu-Pb偏晶合金的快速凝固行为和凝固组织

Rapid solidification behavior and microstructure of highly undercooled Cu-Pb monotectic alloy melts

用熔融玻璃净化与循环过热相结合的方法,研究了亚偏晶Cu-25％Pb合金,Cu-37.4％Pb偏晶合金和过偏晶Cu-40％Pb(质量分数)合金过冷熔体凝固行为和凝固组织的演化规律,以及Cu-37.4％Pb偏晶合金的过冷度对磨损率的影响.研究表明:在过冷亚偏晶Cu-25％Pb台金熔体凝固过程中先形成α(Cu)初生相,随着过冷度的增大,凝固组织经历粗大枝晶重熔形成的细化枝晶向准球状晶粒演化的过程;在过冷Cu-37.4％Pb偏晶合金熔体凝固过程中初生相为L2相,当过冷度在20-150 K区间时,得到第二相S(Pb)弥散在α(Cu)枝晶间的凝固组织,并且在该过冷区间内随着过冷度的增加,材料的磨损率也逐渐降低;在过冷过偏晶Cu-40％Pb合金熔体凝固过程中初生相为L2相,在过冷度区间42-80 K时,得到以偏晶胞形式分布的凝固组织.

The solidification behavior and structural evolution of Cu-Pb monotectic 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, α(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, L2 liquid phase nucleates ahead of α(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.