Mechanical Performances And Effects Of Hydrogen On The Vanadium Alloys As Fusion Reactor Materials

Vanadium alloys are better than ferritic/matensitic as attractive candidate materials for neutron interactive structural components of fusion energy system, because of their high temperature strength, high thermal stress factor, low activation for neutron irradiation and so on. Now it would be attention as a new kind of engineering material, especially for using in thermal reactors. Vanadium alloy is considered as one of the perfect wall materials of fusion reactor. Vanadium alloys can withstand higher heat load than stainless steel because of higher creep strength. It has less impact on environment, low radioactivity, low decay heat and low contact radiation dose rate for long time, and it can recycle. These properties offer it good safety and friendly environmental features. Furthermore, vanadium alloys have good compatibility with liquid metal, do not react with alkali metal, so it is likely to be used in cooling system with liquid metal fluid. Vanadium alloys have good machining performance;it can be rolled into sheets, extruded as tube and welded.It is mostly concerned that vanadium alloys have relatively high affinity withinterstitial impurities as H> Ch N% C and so on. Hydrogen-induced hardening and embrittlement are still important issues for the effect of hydrogen on vanadium alloys. For further studying the mechanical property of vanadium alloys with hydrogen used in engineering, this paper chooses two kinds of vanadium alloys. The mechanical properties and SEM observation of the fracture surfaces were investigated, from which the effect of hydrogen on vanadium alloys was analyzed. The tensile behaviors of vanadium alloys with hydrogen and without hydrogen were studied on different tensile rate> different constant loading time and different loading stress, by measuring hydrogen concentration after and before tension and analyzing mechanical properties. The change of hydrogen and mechanical properties were investigated, beside those, the microstructure of fracture surface was observed.The testing results indicate: hydrogen-induced hardening improved strength of vanadium alloys, and decreased toughness, which were also proved by fracture surface features. Hydrogen concentration affected the increment of strength as well. In the engineering application, vanadium alloys operate under loading, so the effect of stress on hydrogen behaviors of vanadium alloys can cause the change of mechanical properties. In the process of tensile, hydrogen released from vanadium alloys, and on the high stress loading, temperature creep can be occurred for vanadium alloys. These phenomena show hydrogen-induced hardening, hydrogen-induced unsteady change of elastic property and strength. These could bring about additional safety issues and should be further studied for a fully understanding of the behavior to avoid such instability.