摘要
Liquid ternary Fe47.5Cu47.5Sn5 alloy displayed dual solidification mechanisms when it was undercooled by up to 329 K （0.19TL）. Below a critical undercooling of about 196 K, it solidified just like a normal peritectic alloy, even though metastable phase separation occurred to a microscopic extent. Once bulk undercooling exceeds 196 K, macroscopic segregation played a domi- nant role in solidification. In both cases, the solidification process was always characterized by two successive peritectic trans- formations： firstly primary yFe dendrites reacted with liquid phase to form （Cu） phase, and subsequently the （Cu） phase reacted with residual liquid phase to yield β-Cu5.6Sn intermetallic compound. The primary yFe dendrites achieved a maximum growth velocity of 400 mm/s and experienced a growth kinetics transition as a result of macrosegregation. Since the （Cu） phase was both the product phase of the first peritectic transformation and also the reactant phase for the second peritectic transformation, it appeared as two layers in solidification microstructures due to the microsegregation of Sn solute. The boundary continuity between the macroscopically separated Fe-rich and Cu-ricb zones was enhanced with the increase of undercooling.
Liquid ternary Fe 47.5 Cu 47.5 Sn 5 alloy displayed dual solidification mechanisms when it was undercooled by up to 329 K(0.19T L).Below a critical undercooling of about 196 K,it solidified just like a normal peritectic alloy,even though metastable phase separation occurred to a microscopic extent.Once bulk undercooling exceeds 196 K,macroscopic segregation played a dominant role in solidification.In both cases,the solidification process was always characterized by two successive peritectic transformations:firstly primary Fe dendrites reacted with liquid phase to form(Cu) phase,and subsequently the(Cu) phase reacted with residual liquid phase to yield-Cu 5.6 Sn intermetallic compound.The primary Fe dendrites achieved a maximum growth velocity of 400 mm/s and experienced a growth kinetics transition as a result of macrosegregation.Since the(Cu) phase was both the product phase of the first peritectic transformation and also the reactant phase for the second peritectic transformation,it appeared as two layers in solidification microstructures due to the microsegregation of Sn solute.The boundary continuity between the macroscopically separated Fe-rich and Cu-rich zones was enhanced with the increase of undercooling.
基金
supported by the National Natural Science Foundation of China (Grant Nos. 51101123 and 50971105)
the Fundamental Research Fund of Northwestern Polytechnical University (GrantNo. JC201050)
