TEM Investigation Of The Mechanism Of Irradiation Harding For Ion-irradiation V-4Cr-4Ti And V-5Cr-5Ti Alloys

With the development of international fusion reactor project,more attention has been paid on the study of radiation damage of nuclear structure material.Vanadium alloys are considered to be one promising candidate low activation structural material for fusion reactor because of their excellent low activation characteristics,good high temperature strength and radiation resistance.Studying the microstructure of vanadium alloys irradiated is very important to understand the macroscopic mechanical properties and the mechanism of irradiation damage and develop new vanadium alloy materials.V-4Cr-4Ti and V-5Cr-5Ti alloys were irradiated with He ions at room temperature.The microstructures of materials such as dislocations and helium bubbles after irradiation were observed and characterized by transmission electron microscopy.The thickness of the sample was measured by CBED and EELS.The study found that:The actual extinction distance of the sample measured by CBED was matched with the effective extinction distance taking into account the offset vector value.Through modeling analysis,it could be seen that the He ions introduced during the irradiation did not nearly affect the extinction distance.This paper argued that CBED was more accurate.Compared with the thickness of the sample measured by CBED,the thickness measured by EELS was larger,which was attributed to the influence of the amorphous layers.He ions were implanted into vanadium alloys at room temperature,resulting in a large number of defects such as small He bubbles.The average size and density of the He bubbles in vanadium alloys are increasing with the increase of irradiated displacement damage.However,the average size and density of the He bubble in V-5Cr-5Ti alloy were both less than these in V-4Cr-4Ti at the same irradiation conditions,which indicated that the anti-radiation performance of V-5Cr-5Ti alloy was better.It also could be found that irradiation swelling rate of vanadium alloy has a linear relation with the displacement of irradiation damage.The swelling rate of V-5Cr-5Ti alloy was slightly lower than V-4Cr-4Ti alloy,which further illustrated the anti-radiation performance of V-5Cr-5Ti alloy was better than that of V-4Cr-4Ti alloys.The reaction of dislocations and helium bubbles in vanadium alloys conformed to the Orowan mechanism.The calculated hardness increments caused by helium bubbles were compared with the experimental values measured by nanoindentation experiments.It was found that the irradiating hardening of vanadium alloys was mainly attributed to helium bubbles.