Al–Zn–Mg–Cu系合金T4材の拡管加工性に及ぼす復元処理の影響

抄録

Severe working is required for structural materials in some cases for the purpose of reducing costs. The cost becomes higher with the increasing production process when working from O temper condition; therefore working from T4 temper condition is then desirable. In this study, the effect of the reversion process on the cold workability, especially the expanding of an Al–Zn–Mg–Cu alloy tube in T4 temper was investigated. The suitable condition of reversion treatment on which the hardness decreased and the workability which had decreased by long term room temperature aging improved was 433 K for 45 s. In the case of long time reversion at relatively low temperature, e. g., 393 K for 3600 s, the workability became better than that without the reversion treatment while the hardness after the reversion treatment became equal to that without the reversion treatment. Improvement of workability is due to the homogeneous deformation owing to the second–phase particles (η′and η phase) which precipitated during the reversion heat treatment. It was then suggested that the reversion heat treatment at a relatively lower temperature for a longer time could be industrially useful.