Abstract
The diffusivity is an important variable in a number of metallurgical phenomena. However, until recently few quantitative data have been availiable on diffusion phenomena of iron in liquid nonferrous metals. Therefore, we attempted to determine the diffusion coefficients of iron in molten Al, Zn, Sn and Mg.
The results obtained were as follows:
1) In some examinations of diffusion run in molten Zn by semi-infinite medium, the unexpected distributions of iron concentration in molten Zn were observed. These phenomena were considered as “precipitation” originating from the difference of specific gravity. Therefore, prior to determining the diffusion coefficient of iron, the solubility of it in molten Zn was measured by some methods in the temperature range from 450°C to 700°C. The solubility measured in this work is very small compared with the value shown in literatures.
2) The diffusion coefficients of iron in molten Al, Zn, Sn and Mg were determined by Stefan and Kawalki's method. The diffusion coefficients determined were:
In molten Al (700-900°C) DFe=37×10-3 exp (-4, 000/RT) cm2/sec In molten Zn (470-900°C) DFe= 27×10-2 exp (-8, 700/R T)
In molten Sn (500-900°C) DFe=19×10 exp (-3, 000/R T)
In molten Mg (800-900°C) DFe=17×10-3 exp (-2, 500/RT)
3) Above results were compared with the calculated values by some representative equations. The obtained diffusion coefficients of iron in this work agree well with the calculated values by the Li-Chang's equation, using Goldshmit's ionic radius of iron for radius of diffusion molecule. This result shows that cations of iron diffuse in molten non-ferrous metals, because the activation energy of diffusion is of the same order as in the nonmetallic solutions.
