Sn-Cu钎料液态结构与黏度分子动力学研究

应用基于MEAM势的分子动力学模拟,研究了Sn-0.7%Cu和Sn-1.8%Cu两种钎料在503~773K液态结构和黏度的变化规律.首先,通过模拟数据分别计算得出不同温度下两种钎料熔体的双体分布函数g(r)以及Cu元素和Sn元素在两种钎料合金中的均方位移,由均方位移得出自扩散系数,然后依据Stokes-Einstein方程计算出两种钎料的液态黏度,模拟计算液态黏度结果与实验数据基本一致.随着温度降低,黏度呈上升趋势,并且在黏度曲线上均出现跳跃点,以跳跃点为分界点,黏度曲线可以明显分为低温区和高温区.模拟得到的双体分布函数曲线符合热力学普遍规律,随着温度降低,第一峰和第二峰都变得更尖锐一些.

Investigation on liquid structure and viscosity of Sn-Cu solders by molecular dynamics

The liquid structure and melt viscosities of Sn-0.7%Cu and Sn-1.8%Cu were investigated from 503 K to 773 K with the modified embedded atom method (MEAM) in molecular dynamics (MD) simulations. The pair correlation function (PCF) g(r) , the mean square displacement and the self-diffusion coefficients of Cu and Sn in solders at different temperatures were calculated. Then, the viscosity of the two liquid solders was obtained through Stokes-Einstein equation, and the calculated results match experimental ones very well. The viscosity increases with the temperature decreasing. Meanwhile, there is a turning-point on each viscosity temperature curve so that they can be divided into two temperature zones, which can be called low temperature zone and high temperature zone respectively. With the temperature descending, the first and the second peaks of pair correlation functions become sharper and sharper, which conforms to thermodynamics rule.