With the high-temperature viscometer and magnetic susceptibility measurement device designed by our group,the viscosity and the magnetic susceptibility of the Cu65Sn35 melt were measured during the cooling process.An anomalous change can be found in the curves of viscosity and magnetic susceptibility at a certain temperature.The structure of the melt was studied by the high-temperature X-ray diffractometer.The anomalous change also can be found in the pair distribution function,correlation radius,and coordination number at the approximate tem-perature,which shows the microstructural change of the Cu65Sn35 melt.From the results,it was confirmed that the Cu6Sn5 compound occurs in the melt,which leads to the structural change of the melt.
The liquid structure of Al71.6 Ge28.4 eutectic alloy was studied by X-ray diffractometer.For the liquid alloy Al71.6 Ge28.4,the structure has no change while the order increases with the decreasing temperature from 1150°C to 550°C.Meanwhile,the correlation between liquid structure and solid structure has also been analyzed by "the nanocrystal model".It is shown that the melt consists of 72.8% α clusters and 27.2% β clusters,but the liquid structure and solid structure have striking difference,which is one of the reasons to obtain a large undercooling easily for this alloy.
The effect of yttrium on the thermal stability and crystallization behavior of Nd-Fe-Al-Ni amorphous alloys was investigated using X-ray diffraction (XRD), differential scanning calorimeter (DSC), and transmission electron microscopy (TEM).The results indicated that the as-cast Nd60Fe20Al10Ni10–xYx(x=0, 2) amorphous alloys were fabricated with some quenched-in crystals, which could be restrained by Y. With the effect of yttrium, both the crystallization temperature and exothermic peak shifted to higher temperatures, illustrating that the ther- mal stability could be improved. The addition of Y changed the crystallization process and final crystallization results. Moreover, the crystal- lites in the amorphous matrix became more homogeneous and smaller. Meanwhile, Y was useful for the passivation of oxygen in chemistry and restrained the negative effect of oxygen. The activation energies of the start of crystallization and peaking were 1.21 and 1.16 eV, respec- tively, according to the Kissinger equation.
A nanocrystal model for liquid metals and amorphous metals has been developed. With the nanocrystal model, the broadening peak profiles (BPPs) of Cu, Al, Al65Cu20Fe15 alloy, Cu70Ni30 alloy and Fe50Si50 alloy were gained by broadening the X-ray diffraction (XRD) peaks of a crystal lattice. By comparing the BPPs with the XRD intensity curves measured on the liquid metals, it is found that the BPPs are closely in agreement with the XRD intensity curves, respectively, except the Fe50Si50 alloy. Therefore, the nanocrystal model can be used to determine if the atomic cluster structure of the liquid metal is similar to the structure of its crystal lattice.
X.L. Tian, C.W. Zhan, J.X. Hou, X.C. Chen and J.J. Sun Key Laboratory of Liquid Structure and Heredity of Materials, Ministry of Education, Shandong University, Jinan 250061, China
The liquid structure of Co79.5Sn20.5 eutectic alloy has been investigated by means of X-ray diffraction. The result shows that the liquid structure of Co79.5Sn20.5 alloy displays quite stable from 1350℃ to 1150℃ although the short-range order increases with temperature decreasing.In addition,the correlation between the liquid structure and solid structure also has been analyzed by"the nanocrystal model".It is shown that the melt of Co79.5Sn20.5 alloy consists ofβCo3Sn2 clusters andβCo clusters, indicating that the liquid structure and solid structure of Co79.5Sn20.5 eutectic alloy are strikingly similar.
SUN JianJun 1,2 ,ZHENG HongLiang 1 ,SHI XinYing 1 &TIAN XueLei 1 1Key Laboratory for Liquid-Solid Structural Evolution and Processing of Materials(Ministry of Education),Shandong University, Jinan 250061,China
