$⟨001⟩$ edge dislocation nucleation mechanism of surface blistering in tungsten exposed to deuterium plasma

The mechanism of tungsten (W) blistering under deuterium (D) plasma exposure is still under investigation. To clearly demonstrate the microstructure and nucleation mechanism of blistering on W exposed to D plasma, special recrystallized W disc samples were prepared and electropolished with back-thinned method for TEM observation. D plasma exposure (2.0  ×  10²⁶ D m⁻², 573 K) brought it numerous intra-granular blisters and protrusions on W with typical orientation dependence. TEM observation revealed the intra-granular blister microstructure that substantial dislocations were generated on the center and edge of blister via severe plastic deformation of blister cap. Dislocation tangles formed by dislocations from blisters were revealed and supposed to be the nucleation of intra-granular blister. By using the g · b  =  0 and g · b  ×  u  =  0 criterion, 〈0 0 1〉 dislocations with edge component were identified which were generated by 〈1 1 1〉 edge dislocation interaction in dislocation tangles. A {0 0 1}〈0 0 1〉 edge dislocation nucleating and blistering mechanism based on previous works is proposed, and by applying which blistering in recrystallized W could be well explained. Dedicated experiments demonstrated that intra-granular blister formation depends on local dislocation density which validated the mechanism. (paper)