Cu-Be合金の動的再結晶に及ぼすCo微量添加の影響
1994 年 58 巻 1 号 p. 15-22
詳細
1994 年 58 巻 1 号 p. 15-22
The effect of small additions of Co on dynamic recrystallization (DRX) of Cu-Be alloys was studied by means of tensile testing and microstructural observation at 1123 K and at strain rates from 10−5 to 10−1 s−1. The high-temperature flow curves were scarcely affected by the addition of Co and, in contrast, the room-temperature hardness of the hot-deformed matrix are clearly dependent on it. Such age hardening took place more clearly during hot deformation compared with static annealing of the Cu-Be-Co alloys. On the other hand, cuboid-shaped inclusions existing only in the Cu-Be-Co alloys were identified as the (CoCu) Be intermetallic compound. Their growth rate is accelerated by hot deformation. DRX of the Cu-Be alloy was almost the same as that of pure Cu in the whole range of deformation condition, and also that of the Cu-Be-Co alloys only in the region of flow stresses higher than 50 MPa. In the lower stress region, DRX as well as the growth of (CoCu) Be particles took place simultaneously during deformation, leading to the evolution of finer DRX grain structures. It is concluded that the critical condition in which the Cu-Be-Co alloys change the DRX characteristics is Ds=Dlim. (Here Ds and Dlim are the stable DRX grain size and the final grain size stabilized by second phase particles, respectively.) When Ds<Dlim in the higher stress region, dynamic grains can be controlled by DRX, leading to Ds. Conversely, when Ds>Dlim in the lower stress region, they can be controlled by second phase particles, leading to Dlim.
