Research Of Liquid Structures And Electrical Resistivites And Solidification Structure Of Sb-based Alloys

The liquid structure and solidification structure of some Sb-based alloys have been studied with X-ray diffraction and measurements of physical properties as main means, scanning electron microscope (SEM) and energy disperse spectroscopy (EDS) as assistant means in this paper. The purpose of this article is to systematically study the temperature dependence of the structure and physical properties. Furthermore, exploring the correlation between liquid structure and solidification structure lay the theoretical foundation for researching new materials.The result of high temperature X-ray diffraction for Ni2Sb98alloy show that the nearest atomic distance keep stable in the whole temperature range. However, the coordination number is about7, and the ratio of the second nearest atomic distance to the nearest atomic distance is larger than that of SC structure. These reveal that the Peierls distortion is almost destroyed in liquid Ni2Sb98alloy. The covalent bonding structure is reflected in the first peak of. The formation of NiSb associates leads to the CSRO structure and causes the split of the second peak of structure factors and pair correlation functions. The variation of the viscosity obeys the Arrhenius law except the abrupt point at the temperature740℃, and the electrical resistivity changed abnormally at about750℃during the cooling process. It is interesting that the resistivity signal does not go down but go up when melt enter into undercooling zone. The study of solidification structure for NiSb98alloy under different cooling process indicates that the special intermetallic compound NiSb is widely existed in microstructure of NiSb98alloy at general cooling rate and the transformation from NiSb to NiSb2needs long time to react completely. Moreover, the strip-shaped NiSb phase distribute regular in the Sb matrix with the size of about500nm in some areas according to SEM. However, the shape of NiSb2phase is irregular when keep890K for10h during the solidification process.The DSC of Ag-Sb alloys have been studied in this paper. There are two exothermic peaks in the cooling curve of DSC for Ag56Sb44eutectic alloy, which means that biphase separation appears. Moreover, the DSC curves indicate that the making and breaking of eutectic structure brings more changes about the amount of heat only when the Sb content is very high. There are abnormal peaks in the DSC heating curve of both Ag59Sb41alloy and Ag40Sb60alloy,642℃and636℃respectively. Comparing the liquid electrical resistivities of different Ag-Sb alloys finds that the resistivity gradually increases with the decrease of temperature for Ag67.7Sb32.3hypoeutectic alloy and Ag59Sb41eutectic alloy. The absolute value of the temperature coefficient of resistivity becomes larger in undercooling zone. The resistivity decreases at the moment of solid phase precipitate in melt. To hypereutectic alloys, resistivity decreases linearly with the temperature decreasing. The resistivity increases abruptly when the primary phase Sb precipitates. Though the behaviors of resistivities of different Ag-Sb alloys are different in normal melt, the behaviors of resistivities in undercooling zone are the same. The study of solidification structure for Ag-Sb alloys indicates the hypoeutectic alloy grows in typically dendritic growth pattern, and the eutectic structure surrounds the ε phase. The morphology and microstructure of eutectic structure are varied. They are different with traditional eutectic structure. Hypereutectic alloy is incline to grows in isometric growth pattern. And the e phase surrounds Sb phase in the microstructure of high Sb content alloy.