1990 年 56 巻 526 号 p. 1417-1420
The relationship between ductility at creep rupture and the change in the creep fracture mechanism has been discussed. The Ni-NiO eutectic alloys have considerably greater elongation at failure than pure Ni. A creep rupture strain has been divided into three groups of strains; i. e., strain for primary creep regions, for steady-state creep regions and for tertiary creep regions. Both stress and temperature dependence of the amount of these three strains have been investigated. The strain corresponding to the tertiary creep region increases with increasing stress. Consequently, the rupture strain for both materials increases. The rupture strain for both materials linearly increases with the strain for the steady-state creep region. It is suggested that greater elongation in Ni-NiO alloys may be attributed to the high ductilitiy in the nickel matrix which is produced by the addition of nickel oxide. The change in the fracture mechanism from intergranular creep fracture to transgranular creep fracture results in the increase of strain corresponding to the tertiary creep regime.