Influence of hydrogenation on the microstructure and crystallization of Zr-Cu-Ni-Al-Y metallic glass

Zr-Cu-Ni-Al-Y metallic glass was electrochemically charged with hydrogen. The hydrogen content in the hydrogenated specimen was derived from the shift of scattering maxima of the X-ray diffraction (XRD) spectra. The microstructures of the untreated Zr-Cu-Ni-Al-Y metallic glass and the hydrogenated specimen have been studied using conventional transmission electron microscopy, high-resolution transmission electron microscopy and energy-dispersive X-ray spectrometry as well as XRD. The untreated Zr-Cu-Ni-Al-Y specimen was found to be almost totally amorphous with a trace amount of yttrium oxide. The addition of the rare-earth element yttrium is beneficial for decreasing the oxygen content in the matrix. Some nanosized precipitates have been found in the hydrogenated specimens. The crystallization of the precipitates was found to consist of two stages. The Zr(Cu, Ni, Al, Y) precipitates segregate in the first stage, while the formation of crystalline ZrH₂ dominates the second stage. The size, amount and distribution of the nanocrystals are mainly related to the charging current and time.