Characterization of microstructure in hydrogen ion irradiated vanadium at room temperature and the microstructural evolution during post-irradiation annealing

• Interstitial dislocation loops with Burgers vector of 1/2<111> were predominant.
• Less than 10% of 1/2<110> dislocation loops were present in pure vanadium.
• No <100> or vacancy type loops were present in pure vanadium.
• Density and size of dislocation loops changed sharply at temperature above 450 °C.
• Bubble coalescence occurred when annealing temperature was higher than 500 °C.

The microstructure of pure vanadium after hydrogen ion irradiation at room temperature to a fluence of 1 × 1017 ions/cm2 (and 5 × 1016 ions/cm2) was investigated by transmission electron microscopy (TEM). Small dislocation loops (black spots) and cavities are formed after the irradiation. The nature and Burgers vector of dislocation loops formed in vanadium was characterized using g·b technique and inside–outside method. Interstitial dislocation loops with Burgers vector of 1/2 < 111 > predominantly formed with less than 10% of 1/2 < 110 > type. No < 100 > type or vacancy type dislocation loop formed. The microstructural evolution during the annealing process was also studied. Density and size of dislocation loops changed sharply when the annealing temperature was lifted up to 450 °C. When the annealing temperature was higher than 500 °C, bubble coalescence occurred with some large hydrogen bubbles formed.