Bi熔体粘滞性的非连续变化现象

金属熔体的粘滞性是液态金属原子迁移能力的一种表现，反映了原子间结合力的大小，是重要的熔体敏感物理性质之一，从中能得到许多关于液态结构的信息，同时也是重要的铸造工艺参数。Bi熔体的粘度一温度曲线关系表明，粘度随着温度的降低而增加，但并不连续，计算可知，高温区域的粘流活化能E值最小，低温区域的最大，中温区域的处于两者之间。随温度升高，流团尺寸vm在减小。结合DSC曲线分析认为，粘度异常变化区域是Bi熔体由不均匀向均匀原子结构非连续变化所引起的，与熔体中原子健的转变密切相关。

Discontinous Viscosity Variation of Bi Melt

The viscosity of metal melt is one of the most important sensitive physical feature which represents the ability of the atom moving of metal melt, and reflects the binding energy between atoms. From it, we can get lots of messages of melt microstructure ,at the same time,it is also a important parameter of foundry technics.The viscosity-temperature curve of Bi melt showed that the viscosity values dropped with the increase of temperature, however, the discontinuous changing took place in the viscosity curve. Viscosity of Bi melt can be divided into three parts according to its change rate with temperature. A high temperature zone, moderate temperature zone and low temperature zone can be used to describe the viscosity behavior.Combining the DSC analysis,the abnormal phenomenon was explored from the microscopic structure viewpoint. It was assumed that the change from a homogeneous atom configuration to an inhomogeneous one led to the temperature-dependent discontinuous variation, in relation to the bond transformation with the increase of temperature in the Bi melt.