Ostwald ripening of precipitates during two successive heat treatments performed at different temperatures
✍ Scribed by Manfred Mrotzek; Eckhard Nembach
- Publisher
- Elsevier Science
- Year
- 2008
- Tongue
- English
- Weight
- 155 KB
- Volume
- 56
- Category
- Article
- ISSN
- 1359-6454
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✦ Synopsis
Two-stage Ostwald ripening of precipitates has been investigated experimentally and theoretically. A nickel-base alloy in which spherical nano-scale precipitates of the c 0 -phase form served as a model system. Each specimen was heat treated at two successive temperatures T 1 and T 2 in the range 949-1119 K. Thus, monodal as well as bimodal precipitate dispersions were produced. On the basis of an equation published by Wagner, Lifshitz, and Slyozov for isothermal ageing, the function rðt 1 ; T 1 ; t 2 ; T 2 Þ is modeled, where rðt 1 ; T 1 ; t 2 ; T 2 Þ is the average precipitate radius after double ageing and t i is the ageing time at T i . In the case of bimodal c 0 -precipitate dispersions, two average radii are considered. The agreement between measured and calculated values for rðt 1 ; T 1 ; t 2 ; T 2 Þ is within 7%, which is about the same accuracy as that of experimental data determined by transmission electron microscopy. The quoted agreement holds for monodal c 0 -precipitate dispersions as well as for each c 0 -population of bimodal dispersions.