Formation mechanism of layered microstructure and monotectic cell within rapidly solidified Fe62.1Sn27.9Si10 alloy

Abstract

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 1.1107 to 6.5107 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+L2FeSn2 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 Fe phase exhibits a conspicuous solute trapping effect during rapid solidification.