Ti-6Al-2Sn-4Zr-6Mo合金の衝撃靱性に及ぼすミクロ組織因子の影響

Abstract

The instrumented Charpy impact test and dynamic fracture toughness test are carried out on variously heat treated Ti-6Al-2Sn-4Zr-6Mo alloy, and the effect of microstructure on toughness under impact loading is examined.In equiaxed α structural specimens, Charpy absorbed energy (Et) value increases with the increase of solution treatment temperature below 1 123 K, and then decreases with increase of solution treatment temperature above 1 123 K. Et value is strongly influenced by the cooling rate after solution treatment. In equiaxed α structural specimens, the tendency of the change in dynamic fracture toughness (Jd) with solution treatment temperature is similar to that of Et value. However, the degree of the change in Jd value and the effect of cooling rate after solution treatment on Jd value are significantly small. Et and Jd values are remarkably large in acicular structural specimens which are furnace cooled after solution treatment in the β region. In acicular α structural specimens, Et and Jd values increase with the increase of prior β grain size. However, in equiaxed α structural specimens, Et value rather decreases with increase of prior β grain size although Jd value increases. Et and Jd values increase with the increase of the roughness of fracture surface.