Liquid-liquid phase separation in highly undercooled Ni-Pb hypermonotectic alloys
(1. State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi’an 710072, China;
2. School of Materials Science and Engineering, Xi’an University of Technology, Xi’an 710048, China)
2. School of Materials Science and Engineering, Xi’an University of Technology, Xi’an 710048, China)
Abstract: Liquid-liquid phase separation in the undercooled Ni-20%Pb(mole fraction, the same below if not mentioned) hypermonotectic melts was investigated by the observation of the water-quenched structure and DTA analysis. The results indicate that the number of spherical cells in the water-quenched microstructure increases with dropping temperature, and the cells gather and grow up obviously. The spherical cell origins from L1 phase separated from homogeneous melt, and is the product of monotectic reaction. Both results of the water-quenched structures and DTA analysis prove that liquid phase separation still occurs in the highly undercooled Ni-Pb hypermonotectic alloy melts, and liquid phase separation in the immiscible gap can not be fully inhibited by high undercooling and rapid solidification.
Key words: Ni-Pb hypermonotectic alloy; monotectic cell; high undercooling; liquid-liquid phase separation; water-quenched microstructure