Analysis of Kinetics of Diffusion Induced Recrystallization in Fe Phase of Cu/Fe/Cu Diffusion Couples
Combining the columnar-geometry and boundary-diffusion model by Li and Hillert with the energy balance model by Kajihara and Gust, a new kinetic equation has been obtained to describe the growth rate of the alloyed region due to diffusion induced recrystallization (DIR) in a solution phase of binary systems. The equation has been utilized to analyze quantitatively the kinetics of DIR in the Fe(Cu) system observed by the present authors using Cu/(Fe-4.8 mass%)/Cu diffusion couples. The notation Fe(Cu) means that Cu atoms diffuse into a pure Fe or binary Fe-Cu phase. The observations indicate that the thickness <i>l</i> of the DIR region formed in the Fe phase from each interface increases with increasing annealing time <i>t</i> according to the relationship <i>l</i>=1.58×10<sup>-6</sup>(<i>t/t</i><sub>0</sub>)<sup>0.29</sup> at 1323 K. Here, <i>l</i> and <i>t</i> are measured in m and s, respectively, and <i>t</i><sub>0</sub> is unit time, 1 s. Using the mobility <i>M</i> as the fitting parameter of the kinetic equation, we have obtained the value of <i>M</i>=8.64×10<sup>-13</sup> m<sup>4</sup>/J s and the relationship <i>l</i>= 1.08×10<sup>-6</sup>(<i>t/t</i><sub>0</sub>)<sup>0.33</sup> on the basis of the observations. Through the analysis, it is concluded that <i>l</i> increases in proportion to √<i>t</i> for DIR in a pure metal whereas <i>l</i> increases proportionately with <sup>3</sup>√<i>t</i> for DIR in a solution phase even with a low solute concentration.
- ISIJ international
ISIJ international 37(9), 921-927, 1997-09-15
The Iron and Steel Institute of Japan