Mechanical properties of candidate vanadium alloys for fusion applications

Abstract

The results of tensile and creep tests are presented for three vanadium alloys; namely, V-20Ti, V-15Cr-5Ti, and VANSTAR-7 (V-9Cr-3.3Fe-1.2Zr-0.054C). The effects of controlled amounts of interstitial oxygen (up to 1200 wppm additional) on the mechanical properties and fracture behavior are also discussed. Tests were performed between RT and 800°C. Post-test examinations consisted of SEM fractography. In tension testing, all alloys showed ductile behavior (>15% elongation) and high strength in the noncontaminated condition. V-20Ti was the strongest in tension and VANSTAR-7 the weakest. These results were in general agreement with earlier studies on other heats of these alloys. Contamination with up to 1200 wppm oxygen affected both the tensile properties and the fracture behavior of the alloys to varying degrees. Alloy V-20Ti was the least sensitive to oxygen contamination, while the other two alloys were similar in their response, showing some brittle behavior at the surfaces while maintaining ductile deformation in the bulk; this latter effect is believed due to nonuniform distribution of the oxygen. V-15Cr-5Ti showed the highest creep strength, high (>13%) failure strains, and fracture predominately by ductile shear. The effect of oxygen contamination was not very significant in any of the alloys. All three alloys displayed better creep strength than 20% CW 316 SS at equivalent temperatures.