Investigation of microstructural evolution of irradiation-induced defects in tungsten: an experimental-numerical approach

This study employs an integrated experimental-numerical approach to assess the microstructural evolution of irradiation-induced defects in tungsten (W), which is being considered for fusion applications. A cluster dynamics (CD) model is utilized, and simulations are performed for irradiated disk-shaped compact tension W specimens. Experimental results indicate that the primary irradiation-induced defects in W at temperatures of 400 °C and 600 °C include dislocation loops (½<111> and <100>) and voids. Both experimental and CD results reveal that, at higher temperatures, the ½<111> loop population surpasses that of <100> loops, primarily due to the higher formation free energy of <100> loops compared to ½<111> loops. Given the high mobility of ½<111> loops in W, in the absence of traps, most ½<111> loops are absorbed by sinks or coalesce with <100> loops, leading to a reduced ½<111> loop population, as supported by the CD model. However, the introduction of traps results in an increased ½<111> loop population. The long-term evolution of loops demonstrates that the interaction between ½<111> and <100> loops facilitates the transfer of self-interstitial atoms between loops with different Burgers vectors, causing shifts in the populations of both loop types. The CD model reliably predicts the irradiation-induced microstructure in neutron-irradiated W, considering loops, voids and C15 clusters, while integrating the current state-of-the-art knowledge on radiation damage evolution and W energetics.