A Study of Thermal Creep in the Vanadium Alloy, V-4Cr-4Ti, in a Lithium Environment

Vanadium alloys have been proposed as structural materials for fusion reactors. Although favorable high-temperature properties and low neutron activation encourage its use, it must be used with a coolant that does not allow the addition of interstitial, embrittling impurities to the alloy. Liquid lithium is the only acceptable coolant known at the present time. Unlike behavior with other candidate coolants, the oxygen level in vanadium alloys decrease with time in the presence of lithium.

In order to evaluate the thermal creep of this alloy in the presence of lithium, a set of internally pressurized tube specimens is being exposed to vacuum at another laboratory. To compliment this test, a similar series of specimens is being exposed to lithium in the present study. Deformation of the specimens is measured as a function of time and stress level and the results compared with the vacuum tests. The lower oxygen specimens, those in lithium, are exhibiting higher deformation, consistent with the lower strength resulting from reduced oxygen.