Coarsening behavior of {gamma}{double_prime} precipitates in modified Inconel 718 superalloy
- Univ. of Science and Technology, Beijing (China). Dept. of Materials Science and Engineering
The growth of precipitate particles in precipitation-hardened alloys is very significant, because it can control the long-time mechanical properties of these alloys. The kinetics of this coarsening process have been accounted for in the theory of diffusion-controlled growth, based on the growth theory of Lifshitz and Slyozov and Wagner. The growth of {gamma}{prime} precipitate particles, which have an ordered fcc structure and precipitate coherently in many Ni-containing fcc alloys, follows the d {proportional_to} t{sup 1/3} law. Another commonly observed strengthening phase in many nickel alloys is {gamma}{double_prime}, which has a bct structure and precipitates coherently with a disk shape. A well-known example of this class of alloy, is the widely used commercial alloy, Inconel 718. Here, the measured coarsening kinetics of separate precipitation of {gamma}{double_prime} is found to be linearly related to the cube root of the aging time at 700 and 730 C. However, the coarsening behavior of {gamma}{double_prime} in a compact morphology of {gamma}{prime} + {gamma}{double_prime} in the modified alloy is different from that of Inconel 718. Initially the coarsening rate is very slow, but eventually it coarsens rapidly. The actual {gamma}{double_prime} particle size distribution of the modified alloy is skewed towards large particle size and differs significantly from the theoretically predicted distribution. TEM observations also confirm the preferential dissolution of {gamma}{double_prime} during coarsening, which could be attributed to the presence of an easy-diffusion path or lies to in a short-circuit diffusion.
- OSTI ID:
- 136942
- Journal Information:
- Scripta Metallurgica et Materialia, Journal Name: Scripta Metallurgica et Materialia Journal Issue: 12 Vol. 33; ISSN 0956-716X; ISSN SCRMEX
- Country of Publication:
- United States
- Language:
- English
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