Fast Penetration of Cu in Ni of Cu/Ni/Cu Diffusion Couples Due to Diffusion Induced Recrystallization
Rapid penetration of Cu in Ni owing to diffusion induced recrystallization (DIR) in the Ni(Cu) system was experimentally examined using the Cu/Ni/Cu diffusion couples consisting of pure Cu single crystals and a pure Ni polycrystalline specimen annealed at 923 and 1023 K in previous studies. The experimental results have been theoretically analyzed to find a new criterion for the occurrence of DIR in the present study. According to the experimental results, the thickness <I>l</I> of the DIR region in the Ni phase increases in proportion to the square root of the annealing time <I>t</I>. Thus, if we define the parameter <I>D</I><sup>h</sup> as the hypothetical diffusion coefficient which gives the overall penetration rate of Cu across the DIR region, the thickness <I>l</I> is described as a function of the annealing time <I>t</I> by the equation <I>l</I>=2√<I>D</I><sup>h</sup><I>t</I>. The temperature dependence of <I>D</I><sup>h</sup> has been obtained from the experimental results and then compared with that of the volume diffusion coefficient <I>D</I><sup>v</sup> of Cu in Ni. From the comparison, it is concluded that the ratio <I>D</I><sup>h</sup>/<I>D</I><sup>v</sup> should be greater than thirty in order for DIR to take place in the Ni(Cu) system.
- ISIJ international
ISIJ international 38(5), 489-494, 1998-05-15
The Iron and Steel Institute of Japan