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

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.