Biaxial thermal creep of two heats of V4Cr4Ti at 700 and 800 °C in a liquid lithium environment

This paper presents biaxial thermal creep results for the vanadium alloy V4Cr4Ti in liquid lithium using US Heat 832665 and two batches of tubing made from NIFS-Heat-2. The tests were performed at 700 and 800 °C over a stress range of 30–120 MPa using pressurized tube specimens. Lithium environments changed C, N and O concentrations in V4Cr4Ti. Oxygen removal from the alloy to lithium was small when there was a significant pickup of nitrogen during exposures. The creep response of V4Cr4Ti was characterized by an inverted primary creep followed by a secondary creep or an accelerating creep up to creep rupture. A normal primary creep was also observed in US Heat 832665 when tested at 700 °C and 120 MPa. Improved creep rupture properties were observed in the JP-NIFS-Heat-2 specimens compared to the US-NIFS-Heat-2 specimens. Creep response of V4Cr4Ti is apparently dependent on the heat, tubing production, and stress and temperature conditions.