Papers by Author: Yan Wu

Abstract: Effects of magnetic field intensity on carbon diffusion in pure iron in the single-phase austenite region were investigated. Specimens of high purity iron (99.99%) were buried in an air-proof melting pot filled up with cementation agent, and respectively subjected to isothermal annealing at 930° for 25 min with a heating rate of 5°C /min, and then cooled in the furnace. A magnetic field with different intensity was applied during the whole heating, isothermal holding and cooling processes. The results showed that the magnetic field annealing obviously hinders the carbon diffusion in the direction perpendicular to the magnetic field direction and this effect increased with the enhancement of magnetic filed intensity.

Abstract: The effect of high magnetic field annealing on the nucleation sites for recrystallized nuclei with {111}<112> orientation in the initial stage of recrystallization in as-annealed interstitial-free (IF) steel sheet were investigated by the SEM-EBSD analysis. Specimens of cold rolled IF steel sheet were annealed at 650°C for 0min and 10min respectively with a 12-tesla magnetic field to obtain a partially recrystallized microstructure. During the magnetic field annealing, they were respectively placed at the center of the applied field with their rolling planes parallel to the magnetic field direction (MD), and with their rolling direction (RD) parallel and normal to the MD, respectively. It was found that different to the non-field annealed specimen, in the field annealed specimens, the {111}<112> oriented recrystallized nulei favored to nucleate in the {111}<112> deformed matrix and not in the {111}<110> deformed matrix. This phenomenon may be attributed to the magnetic ordered state induced by the magnetic field, which might suppress the formation of high-energy grain boundaries between the newly formed nuclei and the deformed matrix.

Abstract: The effects of magnetic annealing on recrystallization and texture evolution in asannealed interstitial-free (IF) steel sheet were investigated by means of X-ray diffraction ODF analysis, SEM-EBSD analysis, and optical microstructure observation. During the magnetic annealing, specimens were placed at the center of the applied magnetic field, with their rolling planes parallel to the field direction (MD) and their rolling direction (RD) normal to the field direction (MD). It was found that the magnetic annealing retards the recrystallization process, but promotes the nucleation at the initial stage of recrystallization. Magnetic annealing did not change the mechanism of recrystallization texture evolution but improved the development of γ-fiber texture during the process of recrystallization, and the magnetically annealed specimen had stronger γ-fiber texture compared with the conventionally annealed specimen; this interesting finding is quite different from the previous work on magnetically annealed IF steel.

Abstract: An experimental setup was designed to study the recrystallization kinetics of Interstitial Free (IF) steel in this work. The 80% cold rolled IF steel foils are heated rapidly to 680°C, 730°C and 780°C by a salt bath. The recrystallization kinetic curves were obtained by the quantitative analysis of texture components, microstructures and EBSP (electron back-scattering patterns) measurements. With the help of EBSD, the orientations of the recrystallization nuclei are determined. The growth rule of the recrystallization nuclei was analyzed statistically. The effect of nucleus orientation on the formation of the recrystallization texture was investigated.