| Title |
Research Paper - Transformations - : Growth Kinetics of Carbonitride Precipitates in Nb bearing HSLA Steels |
| Authors |
이원범(W . B . Lee); 강기봉(K . B . Kang); 박찬경(C . G . Park) |
| Abstract |
Growth kinetics of Nb(CN) precipitates have been studied in the 0.03wt.% Nb bearing HSLA steel which was compressively rolled at high temperature(850℃∼1000℃) up to 0.3 strain and isothermally held. Interrupted compression test was also carried out to observe the recrystallization phenomena associated with the precipitation at high temperature. The precipitates were analyzed by the TEM. Observed precipitates revealed that they were nucleated heterogeneously at dislocations and spherical shape. The mean particle size of the precipitates were found to increase with increasing time and temperature. The slope obtained from log plot of precipitate diameter versus time was about 0.5, indicating that the growth behavior followed the Zener`s diffusion controlled growth theory. The slope was about 0.3 for the Ostwald ripening region at longer holding time. The nucleation of precipitates was found to retard softening phenomena owing to pinning effect. In ripenening region of precipiates, restart of softening was followed with eliminating of precipitate pinning effect. This result clearly indicate that the growth kinetics of Nb(CN) precipitates affect both the softening and the recrystallization behavior. |