AZ31B マグネシウム合金圧延板の面内圧縮加工および熱処理による室温成形性の向上

To improve the formability of rolled AZ31B magnesium alloy sheets at room temperature, the in-plane direction was restricted by precompression along 0 (rolling direction: RD), 30, 45, 60, and 90° (transverse direction: TD) from the rolling direction of the alloy sheets whose strain levels relative to the transverse direction were either 0.055 or 0.11. To avoid buckling during bending, a special fixture with comb teeth for thin sheet compression has been developed. The strong orientation of the basal rolling texture of the sheet was weakened after in-plane compression, and coarser grains were observed. The stretch formability was also improved. The circumferential strain (εθ) value was dramatically increased from 0.14 (as-received) to 0.30 (precompressed 11.0%) in Mg specimens. Recrystallization and grain growth occurred in grains with higher deformation energy compared with those having less energy after annealing at 250 °C. The intensity of in-plane anisotropy generated at the flange edge of the drawn product could be controlled to some extent by introducing precompressive strain.