The Correlation Study Of The Structure Transition And The Equivalent Susceptibility Change In Melt

In this paper, according to the law of electromagnetic induction, the device measuring the equivalent susceptibility of metals was designed, which can real-time measure the change of the equivalent susceptibility of liquid metals during the cooling process. The theretical analyse was made for the device, and the equivalent susceptibility change of different liquid metals were measured during the cooling process. At the same time, the correlation between the equivalent susceptibility change and the structure transition was also discussed. This work is significant as a new method for the research of the structure transition in liquid metals. The structure of the Pb, Sn and Cu-Sn melt were studied by the measurement of equivalent susceptibility, viscosity and X-Ray diffraction.The relationship between the deferent voltage of the measuring device and the equivalent susceptibility of materials was given by the theoretical analysis of the measuring device. The equivalent susceptibility of materials in alternating magnetic is brought forward, when the contribution of the eddy to the magnetic flux of materials is considered. For different materials, the equivalent susceptibility shows different meaning. The change of the equivalent susceptibility for the ferro-magnetic material reflects the change of the magnetic susceptibility mainly while it mainly reflects the change of the conductivity for the nonferromagnetic materials.The equivalent susceptibility was measured during the cooling process for the ferro-magnetic material Co_79.5Sn_20.5 and the nonferromagnetic materials Cu₇₅Sn₂₅ alloy. When there are structure transition for materials during the cooling process, the equivalent susceptibility also has the corresponding discontinuity for different materials. This result indicates that the different structure transition in liquid state, solidification and the solid state of materials can be characterized by the change of the equivalent susceptibility.The structure of the Pb melt during the cooling process was studied by the measurement of the equivalent susceptibility, viscosity, density and the DSC heat. The curves of different physical properties has a discontinuous point at similar temperature during the cooling process. The correlation radius of the Pb melt obtained from the X-Ray diffraction also has an anomalous point at the approximate temperature. The results of experiments indicate that there is microstructure transition in Pb melt during the cooling process. The structure of the short range order rearrange and the fcc, hcp structure with higher degree order occurred in the melt. The equivalent susceptibility in Sn melt also have anomalous points during the cooling process, which are for the occurrence of the covalent bond in the melt.The results of the equivalent susceptibility and the viscosity indicate there are structure change in Cu₈₅Sn₁₅ the melt during the cooling process, which is the structure transition from the short range order to the medium range order.For the Cu₆₅Sn₃₅ melt, there are two discontinuous points, i.e. the higher and the lower abnormal points of the equivalent susceptibility and the viscosity during the cooling process. During the cooling process, the correlation radius increase abruptly only at the lower abnormal temperature, while the coordination number increase rapid at higher and lower abnormal temperature. The structure change at higher temperature in the melt is for the structure change of the clusters, the coordination atoms in cluster increase abruptly. After the structure change at lower temperature, the coordination number and the position of the coordination layer in the Cu₆₅Sn₃₅ melt are similar with the corresponding values of the solid Cu₆Sn₅ phase. So it is considered that the structure change at lower temperature in the Cu₆₅Sn₃₅ melt is for the occurrence of the solid-like Cu₆Sn₅ phase.