Shape instability during precipitate growth in coherent solids
- Rutgers Univ., Piscataway, NJ (United States). Dept. of Materials Science and Engineering
The effect of coherent elastic strain on shape instabilities during growth of a single precipitate in an elastically anisotropic cubic system is examined. A general phenomenological field approach to phase transformation kinetics is employed. Emphasis has been given to understanding the formation of concave interfaces of a coherent {gamma}{prime} particle in the Ni-based superalloys. It is shown by a two-dimensional computer simulation that the infinite-range and highly anisotropic strain-induced interaction results in a shape transition from circle to faceted square with {l_brace}10{r_brace} habits and rounded corners at the early stage of growth. Then the divergence of solute atom supply at the corners enhances their growth which results in a concave morphology. Vanishing of the supersaturation (transition to the coarsening stage) causes a diffusional relaxation of the concave interfaces back into flat ones, indicating that the concave square is a nonequilibrium shape. A semi-quantitative criterion for the formation of concave shapes is derived. The concentration profile inside the misfitting particle is found to be nonuniform during its growth and coarsening.
- OSTI ID:
- 55337
- Journal Information:
- Acta Metallurgica et Materialia, Journal Name: Acta Metallurgica et Materialia Journal Issue: 5 Vol. 43; ISSN 0956-7151; ISSN AMATEB
- Country of Publication:
- United States
- Language:
- English
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