Rapid solidification of undercooled Cu60Sn30Pb10 monotectic alloy

Rapid solidification of bulk Cu60Sn30Pb10 monotectic alloy was investigated. The obtained undercooling varied from 37 to 173 K. Solidification microstructures showed obvious macroscopic segregation. X-ray diffraction analysis revealed that the top of sample is a ternary_phase section composed of Sn and Pb solid solution phases and ε(Cu3Sn) intermetallic compound phase, the bottom is a Pb-rich solid solution phase section. With the increase of undercooling, ε(Cu3Sn) intermetallic compound phase in the ternary phase section showed a transition from bulk dendrites to refined lamellar microstructure; in addition, while the lamellar spacing was also decreasing. The experiment indicted that the Sn and Pb phases exist as seperated eutectoids. There is a small amount of ε(Cu3Sn) dendrites in the Pb-rich phase. The ε(Cu3Sn) dendrites increase in length with the increase of undercooling and break into pieces under the condition of great undercooling. The Sn solid solution phase always accretes the circumference of ε(Cu3Sn) intermetallic compound phase. Their shape resembles the peritectic microstructure.