Creep mechanism of highly purified V–4Cr–4Ti alloys during thermal creep in a vacuum

Abstract

Pressurized thermal creep tubes of highly purified V–4Cr–4Ti, the NIFS-Heat-2 alloy have been examined following testing in the range 700–850 °C. It was found that the creep stress exponent of the NIFS-Heat-2 alloy is about five and that the characteristic creep mechanism was the dislocation creep usually observed in pure metals. The apparent activation energy of creep deformation is about 210 kJ/mol in the temperature range 700–850 °C. Creep deformation was considered to be controlled by climb-controlled dislocation-glide at 850 °C, where sub-grain boundary structure predominates and consists of dislocation dipole structures and pile-ups of dislocations.