The alloy based on vanadium and other elements is a promising refractory metal material, which has been used as structural material in convertor reactors.
The classification of vanadium alloys can be divided into two categories :(1) ferrovanadium alloys. There are three kinds of alloys containing vanadium 40%, 60% and 80% in common use. (2) Vanadium alloy for nuclear reactors and fusion reactors. Vanstar-7(V-9Cr-3Fe-1.3Zr), VanSTAR-8 (V-8Cr-10Ta-1.3Zr-0.05C), VanSTAR-9 (V-6Fe-5Nb-1.3Zr-0.05C), V-3Ti1Si, V-4Mo, V-9W, etc.
Vanadium alloy has excellent high temperature mechanical properties, better than 304 and 316 stainless steel. It has good corrosion resistance and radiation embrittlement resistance to all kinds of liquid metals. But vanadium alloy is sensitive to hydrogen in embrittlement interstitial element and easy to form compound with oxygen.
(1) Mechanical properties. V-Ti and Vanstar alloys are mainly composed of V-Ti series and Vanstar series. At room temperature, the tensile strength is generally 520 ~ 730MPa, the yield strength is 450 ~ 540MPa, and the elongation is 20% ~ 24%.
(2) Corrosion properties. Vanadium alloy has a high affinity with oxygen, so its resistance to liquid metal corrosion is closely related to the oxygen content in the medium. Vanadium alloys exhibit good corrosion resistance when the oxygen content is lower than 10×10-6 in liquid metal sodium. However, under the conditions of 10×10-6 to dozens of 10×10-6 oxygen content and 600℃ flowing metal sodium, the experiment showed that the corrosion rate of the alloy was as high as 72 ~ 170mg/dm2(24h), and the alloy lost weight and mass migration occurred. Vanadium alloys exhibit similar characteristics in liquid lithium metals.
The alloy ingot with uniform distribution of alloying elements can be prepared by two vacuum melting in consumable vacuum arc furnace or electron bombardment furnace. Alloy ingots can be forged into slabs or tube billets, hot rolled or cold rolled into plates, or extruded into tube billets at 1150℃ and then cold rolled into tubes of various specifications. The intermediate annealing temperature of cold rolling is 850 ~ 900℃. Alloy ingot can be forged into size is 6 ~ 10 mm thin rod, the rotary forging machine forging into ⏀ 3 mm wire billets, finally made into all kinds of wire rod.
Vanadium alloy has been preselected as the fuel cladding material for sodium-cooled fast reactor due to its low neutron capture cross section, high temperature mechanical properties and good corrosion resistance to low oxygen liquid metal. In recent years, Vanadium alloy (V-15CR-5TI) has been used as the structural material of nuclear fusion reactor cladding. It has high operating temperature, good strength, resistance to liquid metal (Li) corrosion, and strong resistance to radiation and thermal stress. Especially under high energy neutron irradiation, it has excellent low induced emission characteristics, and its comprehensive performance is better than stainless steel. However, vanadium alloy has poor weldability, high permeability to tritium and poor oxidation resistance. Vanadium alloys can also be used as materials for superconducting magnets, such as vanadium - gallium superconducting magnet alloys with a magnetic field up to 17.5t.
