Microstructure and Phase Constitution of Fe-Sn Alloy under Different Solidification Conditions
Button-and thin strip-shaped Fe-Sn alloy specimens were prepared by high-frequency induction heating and single-roll technology,respectively,and the phase separation organization and phase constitution of Fe60Sn40 and Fe40Sn60 alloys were comparatively analyzed by using metallurgical microscope,scanning electron microscope,energy spectrum analyzer,and X-ray diffractometer under conventional and rapid solidification conditions.The results show that under the conventional solidification the morphologies of Fe60Sn40 and Fe40Sn60 alloys are significantly different,but the phase constitutions are almost identical,containing five phases of α-Fe,(Sn),Fe3Sn2,FeSn and FeSn2.The Fe60Sn40 alloy shows an encapsulated structure with clear boundary,whereas the morphology of Fe40Sn60 alloy is divided into three regions as per the characterizations,which contains upper dendrites-middle small-sized particles-lower large-sized particles,and the boundaries of each other are vague.On the contrary,the microstructures of the two alloy ribbons under the rapid solidification are similar,that is,the spherical minor-phase particles uniformly distribute in the matrix,and the phase constitution is composed of α-Fe,(Sn),FeSn and FeSn2.The difference in morphologies under the conventional solidification is attributed to the different kinematics of minor-phase particle,and the absence of the Fe3Sn2 phase in the metallic ribbons may be due to the high cooling rate that inhibits the generation of the intermediate phase.
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