Research On Viscosities And Correlated Physical Properties Of Liquid Metals

The micro-structural change of liquid metal can induce the variation of physical properties. The variation of physical properties can indicate the feature of melt micro-structure, which would provide much scientific theory for the controlling of the heredity of melt structure. The physical properties of melt, with special physical meaning, can be easily measured and evaluated. It is of significance to investigate the micro-structure and physical properties of melt both for the physics of condensed matter and for the application of material science.In this paper, the densities of Sb, Bi and Sb-Bi alloy melts, the viscosities of In, Sn and In-Sn alloy melts, the rheological properties of Sb, Bi, Pb, Sn melts have been investigated by employing the physical properties measuring instrument, torsional oscillation viscometer for high-temperature melt, coaxial cylinder viscometer and X-ray diffractometer. The dependences of physical properties on the temperature and other external conditions have been posted. The evolution mechanisms of micro-structure have been discussed.The densities of Sb, Bi and Sb-Bi alloy have been measured systematically at different temperatures using the improved Archimedean method. The results show that the density of Sb melt decreases linearly with the increasing temperature, which is in a good agreement with other literatures. The density values of Bi melt increase as the temperature increases, getting to the maximum:9.9895g/cm³ at the temperature 39°C above the melting point, and then decrease linearly. Compared with others' results, the density of Bi melt is well consistent with the references at high temperature, but there is a distinct abnormal change near the melting point. The densities of Sb-Bi alloys decrease linearly with the increasing temperature and increase with the content percent of Bi. There are abnormal phenomena resembling that of Bi melt at the temperature 30～50K above the liquidus temperature.There is a common characteristic for the viscosities of In, Sn and In-Sn alloy melts that the temperature dependence of these melts follows the Arrhenius formula on the whole. It is different that the viscosity curves change discontinuously. For example, the viscosity of In melt deviates from the fitting curve at the range of 450～600℃, which is in accordance with that of coordination number and correlation radius in the reference. It is considered that the abnormal change of In melt is possibly due to the transition from resembling face centered cubic lattice at low temperature to random close-packed structure at high temperature. The abnormal regions of the viscosity of Sn melt are at 400℃and 810℃, respectively. The DTA-TG result in the reference also shows that there are two thermal peaks at 400℃and 800℃. The abnormal regions of the viscosity for In₈₀Sn₂₀ melt are at about 330℃and 800℃. There are two thermal peaks at 322℃and 800℃in the DSC curve. The viscosity of In₆₀Sn₄₀ melt is distinctly different, decreasing sharply within the scope of 200～250℃. There is a distinct abnormal change for In₆₀Sn₄₀ melt in the temperature dependence of the correlation radius and atomic number of the cluster. The abnormal regions of the viscosity for In₅₀Sn₅₀ and In₃Sn₉₇ melts are at about 350℃and 750℃, respectively. With the logarithmic transformation of the Arrhenius formula, the flow volumes and activation energies of Sn and In-Sn alloys at every temperature zone are calculated. The results show that the flow volumes and activation energies decrease with the increasing temperature. It is noticeable that the flow volumes and activation energies of In₅₀Sn₅₀ melt are larger than those of other melts.In terms of the empirical formulas, surface tension and diffusion coefficient of melt can be calculated accurately from the viscosity measured in this paper.The effect of horizontal permanent magnetic field on the viscosities of Sb, Bi and Sb-Bi alloy has been investigated. It is shown that the viscosities decrease exponentially as the temperature increases and increase with enhancing magnetic intensity. The influence of magnetic field on the viscosities is from the Lorentz force of electrification particle cutting the magnetic line. Compared with the Bi melt, the effect of the magnetic field on the Sb melt is more obvious. The effect of magnetic field on the viscosities of Sb-Bi alloy increases by degrees: Bi₈₀Sb₂₀, Bi₆₀Sb₄₀, Bi₄₀Sb₆₀, Bi₂₀Sb₈₀. A mathematic model with viscosity, temperature and magnetic intensity is put forward. The rheological features of Pb, Sb, Bi and Sn melt have been investigated. According to Newton law, the judgemental criterion of Newtonian fluid is transited from the relationship between shear stress and shear speed to that of torsion and rotate speed. It is shown that the relationships between torsion and rotate speed of Pb, Sb melt are linear, indicating that the melts are Newtonian fluid. But those of Bi, Sn melts deviate from the linear relation obviously at low temperature and high rotate speed, showing Non-Newtonian characteristic. The rheological feature of Sb₂₀Bi₈₀ melt has the same character with that of Bi melt, and Sb₈₀Bi₂₀ melt with the similar feature of Sb melt. It is concluded that Bi and Sb play an important role in Sb₂₀Bi₈₀ and Sb₈₀Bi₂₀ melts.In addition, the rheological features of Pb₇₀Sn₃₀, Pb_38.1Sn_61.9, Pb₂₀Sn₈₀ melts have been explored with the same method. It is indicated that the relationship between torque and rotate speed of Pb_38.1Sn_61.9 melt is linear and the values are stable, but those of Pb₇₀Sn₃₀ and Pb₂₀Sn₈₀ melt show small fluctuations. The rheological feature of melts is related with the evolution of melt micro-structure. It is considered that there are some riched-Pb and riched-Sn clusters in the melt when Pb-Sn alloys melt. The clusters rearranges with the increasing temperature.Based on the experiment results of Bi, Sn melts and in terms of theoretical analysis, a rheological model of melt micro-structure is established.