Nano-creep behavior of Ti-based bulk amorphous alloy after electrochemical hydrogen charging

In the present study, a Ti_32.85Zr_30.21Cu₉Ni_5.28Be_22.66 bulk amorphous alloy was hydrogenated by the electrochemical method. Samples with different H content were obtained by changing the H-charging current density and charging time. X-ray diffraction (XRD), nanoindentation, and positron annihilation experiments were used to investigate the amorphous structure, nanomechanical properties, and positron annihilation behavior of the Ti_32.85Zr_30.21Cu₉Ni_5.28Be_22.66 bulk amorphous alloy after electrochemical hydrogenation treatment. XRD analysis showed that the sample has an amorphous structure after hydrogen charging. Investigation of the nano-creep behavior using a nanoindentation instrument demonstrated that the creep displacement of the amorphous alloy decreases gradually with the increase of hydrogen content, and the creep stress index increases first and then decreases. The addition of hydrogen atoms inhibits the formation of the shear transformation zone (STZ), resulting in a decrease in the size and dimensions of STZ in the amorphous alloy and an increase in the activation energy. Three lifetime components were observed in the uncharged and charged samples, indicating the presence of three size ranges of open volume sites. The average annihilation lifetime of positrons decreases with the increase of current density and time of electrochemical hydrogen charging, indicating that the addition of hydrogen weakens the annihilation behavior of positrons. The defect range of the corresponding amorphous alloy decreases, making the creep behavior difficult to carry out. Compared with the uncharged hydrogenated sample, the Doppler broadening spectra showed that the hydrogenated sample contributes more to the positron annihilation of the core electrons, that is, the W parameter becomes larger and the S parameter becomes smaller. Although the addition of hydrogen affects the positron annihilation behavior, no new defects are generated in the amorphous alloy.