中文摘要：

采用自由落体和单辊急冷技术研究了三元Fe62.1Sn27.9Si10偏晶合金的相分离和组织形成规律,理论分析了两种快速凝固条件下合金的传热特性.自由落体条件下,由于Marangoni迁移和表面偏析势的作用,液滴凝固组织主要形成富Sn相包裹富Fe相的两层壳核结构.随着液滴直径减小,冷却速率和温度梯度增大,促进偏晶胞快速生长.在单辊急冷条件下,随着辊速的增大,冷却速率从1.1×107增大至6.5×107K/s,合金熔体内部的液相流动和相分离受到抑制,凝固组织发生＂九层结构→两层结构→无分层结构＂的转变.同时,凝固过程中FeSn＋L2→FeSn2包晶反应受到抑制,形成与自由落体条件下不同的相组成.EDS分析显示,αFe相在快速凝固过程中发生显著溶质截留效应.

英文摘要：

Ternary Fe62.1Sn27.9Si10 monotectic alloy is rapidly solidified in drop tube with the freely-falling-body techniqual and with melt spinning method separately.The phase separation,the microstructure characteristics,and the heat transfer of this alloy are investigated theoretically.Under free fall condition,the core-shell structure with two layers is formed because of Marangoni migration and surface segregation,where the Sn-rich phase is always located at droplet surface and the Fe-rich phase in the center.With the decrease of droplet diameter,both cooling rate and temperature gradient increase quickly,which facilitates the rapid growth of monotectic cell.With the increase of wheel speed,the cooling rate of alloy ribbon increases from 1.1×107 to 6.5×107 K/s,the fluid flow and the phase separation are suppressed to a great extent,and the ＂nine layers → two layers → no layer＂ structural transition occurs during the rapid solidification of Fe62.1Sn27.9Si10 alloy obtained by the melt spinning method.Meanwhile,the FeSn＋L2→FeSn2 peritectic transformation is also suppressed,thus resulting in different phase constitutions as compared with the case of free fall condition.The energy dispersive spectroscopy（EDS） analysis reveals that the αFe phase exhibits a conspicuous solute trapping effect during rapid solidification.