Simulation of defect evolution in tungsten during annealing by developing a vacancy and interstitial-type defect evolution model

Abstract

In this work, a Vacancy and Interstitial-Type Defect Evolution (VITDE) model is developed to study the annealing and clustering behaviors of the irradiation-induced defect in tungsten (W). The post annealing of W-ion damaging at 300 K (called post-damaging annealing) and simultaneous annealing of W-ion damaging (called dynamic annealing) are simulated. In the post-damaging annealing case, the W is damaged by 20 MeV W-ion irradiation for 1h at 300 K, then the damaged W is annealed for 1h via increasing the temperature to 1000 K. In the dynamic annealing case, the defect evolution under simultaneous damaging and annealing is simulated using the same parameters as Case 1. The simulation results indicate the dynamic annealing case has lower induced defects concentration than the post-irradiation annealing case, which is in qualitative agreement with the experiment. The diffusion of interstitial, vacancy, di-interstitial and di-vacancy, and the cluster properties in the defect annealing are investigated and larger size Vn clusters are observed in dynamic annealing case than in post-damaging annealing case. The dependences of the defect evolution on material temperature (T) and grain size are revealed. By increasing the T, the defect concentration is decreased, which reproduces and explains the experimental result. The Vn trap amount with the reduction of grain size for two cases show a larger difference at T = 400 K, observing the Vn trap amount is unchanged for post-damaging annealing, whereas it is significantly increased by dynamic annealing.