深过冷Cu_(60)Sn_(30)Pb_(10)偏晶合金的快速凝固

Rapid solidification of undercooled Cu_(60)Sn_(30)Pb_(10) monotectic alloy

实现了大体积Cu60Sn30Pb10偏晶合金的深过冷与快速凝固.实验获得的最大过冷度为173K(0.17TL).凝固组织发生了明显的宏观偏析,XRD分析表明,试样上部是由固溶体(Sn),(Pb)相和金属间化合物ε(Cu3Sn)相组成的三相区,下部为富(Pb)相区.在小过冷条件下,三相区中ε(Cu3Sn)相的凝固组织为粗大的枝晶,随着过冷度的增大,ε(Cu3Sn)相细化成层片状组织,且层片间距随过冷度的增大而减小,而(Sn),(Pb)两相始终以离异共晶的方式存在.富(Pb)相区中分布有少量的ε(Cu3Sn)枝晶,枝晶长度随过冷度的增大而增大,且在大过冷条件下发生碎断.(Sn)相在ε(Cu3Sn)相表面形核、长大,其形态类似于包晶凝固组织.

Rapid solidification of bulk Cu6o Sn30 Pbl0 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 a（ Cu3 Sn） intermetallic compound phase, the bottom is a Pb-rich solid solution phase section. With the increase of undercooling, ε（Cu3 Sn） intermetallic compound phase in the ternary phase section showed a transition from bulk dendrites to refined lamellar microstrncture; 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（Cu3 Sn） 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（Cu3 Sn） intermetallic compound phase. Their shape resembles the peritectic microstrncture.