Analysis of dissolution of {alpha} phase in {gamma}/{alpha}/{gamma} diffusion couples of the Fe-Cr-Ni system using analytical solutions for semi-infinite diffusion couples
- Tokyo Inst. of Tech. (Japan). Dept. of Metallurgical Engineering
The dissolution kinetics of body centered cubic (b.c.c.) {alpha}-ferrite in face centered cubic (f.c.c.) {gamma}-austenite matrix was experimentally studied by the authors at 1,373 K using four sets of {gamma}/{alpha}/{gamma} diffusion couples of the ternary Fe-Cr-Ni system. The experimental results were numerically analyzed using a computer calculation technique. In this paper, further analysis of the experimental results were carried out by using analytical solutions of diffusion equations for semi-infinite two-phase diffusion couples of ternary systems on the basis of the following assumptions: (a) the reaction is diffusion-controlled; (b) interdiffusion coefficients in each phase are independent of the composition; (c) coupled-interdiffusion between Cr and Ni is negligible; and (d) molar volumes of the {alpha} and {gamma} phases are the same. The growth rate of the {alpha} phase during the first stage of the reaction is quantitatively reproduced by the calculation using the analytical solution obtained under the exact initial and boundary conditions. Interface-velocity contours in the {alpha} single-phase region give a semiquantitative explanation for the transition from the growth to the dissolution of the {alpha} phase in the {gamma} phase. A further numerical calculation reveals that the interface compositions change with increasing annealing time even in the case where the interface compositions at the first and final stages of the reaction are the same. Such unusual behavior of the change in the interface compositions can be explained semiquantitatively by the combination of the interface-composition contour in the {alpha} single-phase region and the contour of the composition at the center of the {alpha} phase.
- OSTI ID:
- 27907
- Journal Information:
- Acta Metallurgica et Materialia, Vol. 43, Issue 2; Other Information: PBD: Feb 1995
- Country of Publication:
- United States
- Language:
- English
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