高温 2 段階圧縮加工により配向制御した 2 元系 TiAl 合金に生成した微細粒がクリープ特性に及ぼす影響

Abstract

In order to understand the effect of fine grains on creep property of lamellar orientation controlled Ti-43 mol%Al alloy, compressive creep tests were performed. Uniaxial compression process at α single-phase region and related compression process at (α+γ) two-phase region made the lamellar interface almost parallel to the compression process plane. Fine grains were observed around the orientation controlled lamellar colonies after the process at (α+γ) two-phase region. Volume fraction of fine grains increased with the decrease in true strain rate during the process. Further, in the same true strain rate, volume fraction of fine grains increased with the increase in true strain. These characteristics were almost the same in the case of dynamic recrystallization at the single-phase alloy. Thus, the formation of fine grains at (α+γ) two phase region may indicate the occurrence of dynamic recystallization. Minimum creep rate of the processed material increased with the increase in volume fraction of fine grains. The increase of creep rate of the entire material may be due to the preferential creep deformation of formed fine grains by a diffusional creep mechanism.