不同凝固条件下Fe-Sn合金的组织形貌及相组成

Microstructure and Phase Constitution of Fe-Sn Alloy under Different Solidification Conditions

采用高频感应加热和单辊急冷技术分别制备了纽扣状和薄带状的Fe-Sn合金试样,并利用OM、SEM、EDS、XRD等分析手段,对Fe_(60)Sn_(40)和Fe_(40)Sn_(60)合金在常规凝固和快速凝固条件下的相分离组织及物相组成进行了对比分析。结果表明:常规凝固条件下,纽扣状Fe_(60)Sn_(40)和Fe_(40)Sn_(60)合金的凝固形貌差异显著,但物相组成相同,包含α-Fe、(Sn)、Fe_(3)Sn_(2)、FeSn和FeSn_(2)五个相。Fe_(60)Sn_(40)合金呈界线明显的球-冠包裹式结构,而Fe_(40)Sn_(60)合金形貌按组织特征分为上部枝晶-中部小尺寸粒子-下部大尺寸粒子三个区域,且彼此界线不明显。相反,快速凝固条件下合金条带的组织形貌相近,球形第二相粒子均匀分布于基体内,物相由α-Fe、(Sn)、FeSn和FeSn_(2)组成。常规凝固形貌的差异性归因于不同的第二相液滴运动特性,合金条带中Fe_(3)Sn_(2)相的缺失可能是高冷速抑制了Fe_(3)Sn_(2)相的生成。

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 Fe_(60)Sn_(40)and Fe_(40)Sn_(60)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 Fe_(60)Sn_(40)and Fe_(40)Sn_(60)alloys are significantly different,but the phase constitutions are almost identical,containing five phases ofα-Fe,(Sn),Fe_(3)Sn_(2),FeSn and FeSn_(2).The Fe_(60)Sn_(40)alloy shows an encapsulated structure with clear boundary,whereas the morphology of Fe_(40)Sn_(60)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 ofα-Fe,(Sn),FeSn and FeSn_(2).The difference in morphologies under the conventional solidification is attributed to the different kinematics of minor-phase particle,and the absence of the Fe_(3)Sn_(2)phase in the metallic ribbons may be due to the high cooling rate that inhibits the generation of the intermediate phase.