Small-angle neutron scattering of precipitates in Ni-rich Ni-Ti alloys. 1: Metastable states in poly- and single crystals
- ETH Zuerich (Switzerland). Inst. fuer Angewandte Physik
- Risoe National Lab., Roskilde (Denmark)
Two successive metastable regimes of decomposition are revealed in Ni-(10.8--11.9) at.% Ti single crystals and polycrystals by small-angle neutron scattering (SANS) after various aging steps at 853 K. During the first two hours of aging, the Ti concentration in Ti-rich regions grows linearly with time, while their size remains unchanged. After a few hours, an intermediate plateau in the integrated SANS intensity is reached and indicates an intermediate metastable state. This {gamma}{double_prime} state, fully developed after about 12 h, corresponds to coherent non-spherical precipitates containing (18.4 {+-} 2.5) at.% Ti. After 50--100 h, a further increase in Ti concentration in the precipitates sets in, while they grow and tend to form clusters. After 400--1,000 h, a second metastable state, {gamma}{prime}, with (22 {+-} 2) at. % Ti in the precipitates, is reached. The growth rate in this range is higher than for classical coarsening, and very pronounced spatial correlations of precipitates appear along cubic directions.
- Sponsoring Organization:
- Swiss National Science Foundation, Bern (Switzerland)
- OSTI ID:
- 532891
- Journal Information:
- Acta Materialia, Vol. 45, Issue 8; Other Information: PBD: Aug 1997
- Country of Publication:
- United States
- Language:
- English
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