Simulation Of The Irradiation Damage In Tungsten And Tungsten-rhenium Alloy

The energy crisis is becoming more and more serious.As a kind of clean and safety energy,nuclear fusion energy can fundamentally solve the energy problem if it can be used on a large scale.However,the plasma-facing material（PFM）in nuclear fusion reactor would be irradiated by 14MeV high-energy neutrons,which will cause great degradation of the material properties.Therefore,the choice of the PFM is particularly critical.Tungsten（W）has been regarded as the most promising PFM for future fusion reactors due to its advantages of high melting point,low tritium retention and low sputtering etch rate.Some transmutat ion elements,such as rhenium（Re）,osmium（Os）and tantalum（Ta）,will be produced through nuclear transmutation reactions and the precipitations ofσ（WRe）and/orχ（WRe₃）phases will be induced in the case of high-energy neutron irradiations.These precipitates will lead to radiation hardening and embrittlement of the W materials.Therefore,it is of great significance to investigate the effects of Re on the generation of defects and microstructure evolution in W under irradiation conditions.In this paper,we firstly simulated the low-energy（1⁴0keV）collision cascades in pure W using the molecular dynamics method and then compared the number of stable Frenkel pairs（FPs）with that in the previous studies results.The results indicated that the present potential can be reasonably utilised for performing further cascade simulations.Secondly,we mainly simulated the high-energy（100³00keV）collision cascades in pure W and W–Re alloys.The effects of primary knock-on atom（PKA）energy and Re concentration on the defect generation,defect clusters and dislocation loops were analyzed.The results show that the number of stable FPs increases gradually with the increasing PKA energy in pure W and W-Re alloys,and the presence of 5%and 10%Re atoms does not significantly affect either the number of surviving defects or their clustered fractions.However,it potentially leads to the local enrichment of Re atoms in the W–Re system.This feature may drastically reduce the interstitial cluster mobility in W–Re when compared with pure W.In pure W and W-Re alloys,the interstitial-type dislocation loops are dominated by 1/2<111>loops,followed by the mixed 1/2<111>-<100>loops,and there is almost no<100>loops.The vacancy clusters and incomplete vacancy loops are observed,while no complete vacancy-type dislocation loops are formed in the present simulations.The pinning effect induced by the Re atom segregation leads to the lower mobility of the interstitial clusters and interstitial 1/2<111>loops in W–Re alloys than in pure W,thereby suppressing the growth of loops.The high-energy collision cascades cause subcascades and also induce a unique loop configuration that a loop takes the same Burgers vector but located on various habit planes.