In-situ study of heavy ion irradiation induced lattice defects and phase instability in β-Zr of a Zr–Nb alloy

In-situ heavy ion (1 MeV Kr2+) irradiation was carried out to investigate the evolution of irradiation induced lattice defects at room temperature and the stability of β-Zr under irradiation at temperatures ranging from 150 to 350 °C. It was found that the irradiation induced defects started to appear at a dose between 0.5 dpa and 0.75 dpa, which is relatively high compared to the case for α-Zr. The number density of dislocation loops increased exponentially with fluence, with an exponential index ∼3.52. The statistical results show that the electron beam with which in-situ observation was carried out had an influence on the size of the dislocation loops. The g·b analysis shows that dislocation loops with Burgers vector ½<1¯11> and <100> are both present in the sample after irradiation to 1.5 dpa. ω phase particles precipitate out during irradiation at 250 and 350 °C, as a result of the combination of the thermal treatment and irradiation enhanced concentration of point defects.