High temperature performance of highly purified V–4Cr–4Ti alloy, NIFS-Heat1

Abstract High temperature performance tests including tensile, creep and creep-fatigue tests were conducted using specimens from a large ingot of highly purified V–4Cr–4Ti alloys, NIFS-Heat1. The obtained tensile data of NIFS-Heat1 alloys agree well with previous V–4Cr–4Ti alloys data. The most significant effect for the impurity reduction in NIFS-Heat1 alloys was the higher temperature for the appearance of the dynamic strain hardening compared to previous heats of V–4Cr–4Ti. From uniaxial creep tests, a creep-stress exponent of the NIFS-Heat1 alloy is about 5–8 and the characteristic of creep mechanism is the dislocation creep in pure metals. The apparent activation energies of creep deformation ranged from 180 to 210 kJ/mol at a temperature regime from 750 to 800 °C. No significant degradation due to fatigue behavior was observed during creep-fatigue tests. The creep-fatigue behavior was superior to the load-constant creep behavior in the same stress and temperature conditions at a lower stress condition.