Formation of vacancy-type defects and hydride introduced by irradiation in pure titanium

The effect of hydrogen ion irradiation on the formation of hydride and vacancy-type defects in pure titanium was investigated by X-ray diffraction (XRD), Doppler broadening spectrum (DBS), and coincidence Doppler broadening spectrum (CDB) based on slow positron beam. The XRD results showed that γ-TiH was observed in single hydrogen ion-irradiated and hydrogen + deuterium (H + D) sequentially irradiated specimens but not in the single deuterium plasma-implanted sample. This finding indicates that the vacancy-type defects caused by H ion irradiation greatly promoted the formation of γ-TiH. The DBS results showed that for the single D plasma-implanted sample, the damage peak was closer to the surface region and lower compared to the other two samples containing γ-TiH, indicating that vacancy generated by lattice distortion didn't diffuse to the depth of the matrix, and the concentration of that was smaller, which was not conducive to the deuteride formation. For the H + D sequentially irradiated sample, the number of hydrogen-vacancy complexes (HmVn) further increased compared with the single H ion-irradiated sample. Thus, the effective volume of vacancy defects was reduced, which led to the decrease in the S parameter.